test: cleanup IIFE tests

A number of test files use IIFEs to separate distinct tests from
each other in the same file. The project has been moving toward
using block scopes and let/const in favor of IIFEs. This commit
moves IIFE tests to block scopes. Some additional cleanup such
as use of strictEqual() and common.mustCall() is also included.

PR-URL: https://github.com/nodejs/node/pull/7694
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

34 files changed, 667 insertions, 752 deletions

diff --git a/test/gc/test-net-timeout.js b/test/gc/test-net-timeout.js
index ff1d5656ce..2645ccc503 100644
--- a/test/gc/test-net-timeout.js
+++ b/test/gc/test-net-timeout.js
@@ -35,19 +35,16 @@ function getall() {
   if (count >= todo)
     return;
 
-  (function() {
-    var req = net.connect(server.address().port, server.address().address);
-    req.resume();
-    req.setTimeout(10, function() {
-      //console.log('timeout (expected)')
-      req.destroy();
-      done++;
-      global.gc();
-    });
+  const req = net.connect(server.address().port, server.address().address);
+  req.resume();
+  req.setTimeout(10, function() {
+    req.destroy();
+    done++;
+    global.gc();
+  });
 
-    count++;
-    weak(req, afterGC);
-  })();
+  count++;
+  weak(req, afterGC);
 
   setImmediate(getall);
 }
@@ -76,4 +73,3 @@ function status() {
     }, 200);
   }
 }
-
diff --git a/test/parallel/test-buffer-alloc.js b/test/parallel/test-buffer-alloc.js
index 42f8e27046..fead5cd807 100644
--- a/test/parallel/test-buffer-alloc.js
+++ b/test/parallel/test-buffer-alloc.js
@@ -1038,28 +1038,28 @@ Buffer.from(Buffer.allocUnsafe(0), 0, 0);
 
 
 // GH-5110
-(function() {
+{
   const buffer = Buffer.from('test');
   const string = JSON.stringify(buffer);
 
-  assert.equal(string, '{"type":"Buffer","data":[116,101,115,116]}');
+  assert.strictEqual(string, '{"type":"Buffer","data":[116,101,115,116]}');
 
   assert.deepStrictEqual(buffer, JSON.parse(string, function(key, value) {
     return value && value.type === 'Buffer'
       ? Buffer.from(value.data)
       : value;
   }));
-})();
+}
 
 // issue GH-7849
-(function() {
-  var buf = Buffer.from('test');
-  var json = JSON.stringify(buf);
-  var obj = JSON.parse(json);
-  var copy = Buffer.from(obj);
+{
+  const buf = Buffer.from('test');
+  const json = JSON.stringify(buf);
+  const obj = JSON.parse(json);
+  const copy = Buffer.from(obj);
 
   assert(buf.equals(copy));
-})();
+}
 
 // issue GH-4331
 assert.throws(function() {
@@ -1165,30 +1165,30 @@ assert.throws(function() {
 });
 
 // test for common read(U)IntLE/BE
-(function() {
+{
   var buf = Buffer.from([0x01, 0x02, 0x03, 0x04, 0x05, 0x06]);
 
-  assert.equal(buf.readUIntLE(0, 1), 0x01);
-  assert.equal(buf.readUIntBE(0, 1), 0x01);
-  assert.equal(buf.readUIntLE(0, 3), 0x030201);
-  assert.equal(buf.readUIntBE(0, 3), 0x010203);
-  assert.equal(buf.readUIntLE(0, 5), 0x0504030201);
-  assert.equal(buf.readUIntBE(0, 5), 0x0102030405);
-  assert.equal(buf.readUIntLE(0, 6), 0x060504030201);
-  assert.equal(buf.readUIntBE(0, 6), 0x010203040506);
-  assert.equal(buf.readIntLE(0, 1), 0x01);
-  assert.equal(buf.readIntBE(0, 1), 0x01);
-  assert.equal(buf.readIntLE(0, 3), 0x030201);
-  assert.equal(buf.readIntBE(0, 3), 0x010203);
-  assert.equal(buf.readIntLE(0, 5), 0x0504030201);
-  assert.equal(buf.readIntBE(0, 5), 0x0102030405);
-  assert.equal(buf.readIntLE(0, 6), 0x060504030201);
-  assert.equal(buf.readIntBE(0, 6), 0x010203040506);
-})();
+  assert.strictEqual(buf.readUIntLE(0, 1), 0x01);
+  assert.strictEqual(buf.readUIntBE(0, 1), 0x01);
+  assert.strictEqual(buf.readUIntLE(0, 3), 0x030201);
+  assert.strictEqual(buf.readUIntBE(0, 3), 0x010203);
+  assert.strictEqual(buf.readUIntLE(0, 5), 0x0504030201);
+  assert.strictEqual(buf.readUIntBE(0, 5), 0x0102030405);
+  assert.strictEqual(buf.readUIntLE(0, 6), 0x060504030201);
+  assert.strictEqual(buf.readUIntBE(0, 6), 0x010203040506);
+  assert.strictEqual(buf.readIntLE(0, 1), 0x01);
+  assert.strictEqual(buf.readIntBE(0, 1), 0x01);
+  assert.strictEqual(buf.readIntLE(0, 3), 0x030201);
+  assert.strictEqual(buf.readIntBE(0, 3), 0x010203);
+  assert.strictEqual(buf.readIntLE(0, 5), 0x0504030201);
+  assert.strictEqual(buf.readIntBE(0, 5), 0x0102030405);
+  assert.strictEqual(buf.readIntLE(0, 6), 0x060504030201);
+  assert.strictEqual(buf.readIntBE(0, 6), 0x010203040506);
+}
 
 // test for common write(U)IntLE/BE
-(function() {
-  var buf = Buffer.allocUnsafe(3);
+{
+  let buf = Buffer.allocUnsafe(3);
   buf.writeUIntLE(0x123456, 0, 3);
   assert.deepStrictEqual(buf.toJSON().data, [0x56, 0x34, 0x12]);
   assert.equal(buf.readUIntLE(0, 3), 0x123456);
@@ -1277,11 +1277,11 @@ assert.throws(function() {
   buf.writeIntBE(-0x0012000000, 0, 5);
   assert.deepStrictEqual(buf.toJSON().data, [0xff, 0xee, 0x00, 0x00, 0x00]);
   assert.equal(buf.readIntBE(0, 5), -0x0012000000);
-})();
+}
 
 // test Buffer slice
-(function() {
-  var buf = Buffer.from('0123456789');
+{
+  const buf = Buffer.from('0123456789');
   assert.equal(buf.slice(-10, 10), '0123456789');
   assert.equal(buf.slice(-20, 10), '0123456789');
   assert.equal(buf.slice(-20, -10), '');
@@ -1314,7 +1314,7 @@ assert.throws(function() {
     assert.equal(buf.slice(0, -i), s.slice(0, -i));
   }
 
-  var utf16Buf = Buffer.from('0123456789', 'utf16le');
+  const utf16Buf = Buffer.from('0123456789', 'utf16le');
   assert.deepStrictEqual(utf16Buf.slice(0, 6), Buffer.from('012', 'utf16le'));
 
   assert.equal(buf.slice('0', '1'), '0');
@@ -1328,7 +1328,7 @@ assert.throws(function() {
   // try to slice a zero length Buffer
   // see https://github.com/joyent/node/issues/5881
   Buffer.alloc(0).slice(0, 1);
-})();
+}
 
 // Regression test for #5482: should throw but not assert in C++ land.
 assert.throws(function() {
@@ -1337,20 +1337,20 @@ assert.throws(function() {
 
 // Regression test for #6111. Constructing a buffer from another buffer
 // should a) work, and b) not corrupt the source buffer.
-(function() {
-  var a = [0];
+{
+  let a = [0];
   for (let i = 0; i < 7; ++i) a = a.concat(a);
   a = a.map(function(_, i) { return i; });
   const b = Buffer.from(a);
   const c = Buffer.from(b);
-  assert.equal(b.length, a.length);
-  assert.equal(c.length, a.length);
+  assert.strictEqual(b.length, a.length);
+  assert.strictEqual(c.length, a.length);
   for (let i = 0, k = a.length; i < k; ++i) {
-    assert.equal(a[i], i);
-    assert.equal(b[i], i);
-    assert.equal(c[i], i);
+    assert.strictEqual(a[i], i);
+    assert.strictEqual(b[i], i);
+    assert.strictEqual(c[i], i);
   }
-})();
+}
 
 
 assert.throws(function() {
diff --git a/test/parallel/test-buffer.js b/test/parallel/test-buffer.js
index f3ab74902b..7f51b690fa 100644
--- a/test/parallel/test-buffer.js
+++ b/test/parallel/test-buffer.js
@@ -1054,28 +1054,28 @@ Buffer(Buffer(0), 0, 0);
 
 
 // GH-5110
-(function() {
+{
   const buffer = new Buffer('test');
   const string = JSON.stringify(buffer);
 
-  assert.equal(string, '{"type":"Buffer","data":[116,101,115,116]}');
+  assert.strictEqual(string, '{"type":"Buffer","data":[116,101,115,116]}');
 
   assert.deepStrictEqual(buffer, JSON.parse(string, function(key, value) {
     return value && value.type === 'Buffer'
       ? new Buffer(value.data)
       : value;
   }));
-})();
+}
 
 // issue GH-7849
-(function() {
-  var buf = new Buffer('test');
-  var json = JSON.stringify(buf);
-  var obj = JSON.parse(json);
-  var copy = new Buffer(obj);
+{
+  const buf = new Buffer('test');
+  const json = JSON.stringify(buf);
+  const obj = JSON.parse(json);
+  const copy = new Buffer(obj);
 
   assert(buf.equals(copy));
-})();
+}
 
 // issue GH-4331
 assert.throws(function() {
@@ -1191,30 +1191,30 @@ assert.throws(function() {
 });
 
 // test for common read(U)IntLE/BE
-(function() {
-  var buf = new Buffer([0x01, 0x02, 0x03, 0x04, 0x05, 0x06]);
-
-  assert.equal(buf.readUIntLE(0, 1), 0x01);
-  assert.equal(buf.readUIntBE(0, 1), 0x01);
-  assert.equal(buf.readUIntLE(0, 3), 0x030201);
-  assert.equal(buf.readUIntBE(0, 3), 0x010203);
-  assert.equal(buf.readUIntLE(0, 5), 0x0504030201);
-  assert.equal(buf.readUIntBE(0, 5), 0x0102030405);
-  assert.equal(buf.readUIntLE(0, 6), 0x060504030201);
-  assert.equal(buf.readUIntBE(0, 6), 0x010203040506);
-  assert.equal(buf.readIntLE(0, 1), 0x01);
-  assert.equal(buf.readIntBE(0, 1), 0x01);
-  assert.equal(buf.readIntLE(0, 3), 0x030201);
-  assert.equal(buf.readIntBE(0, 3), 0x010203);
-  assert.equal(buf.readIntLE(0, 5), 0x0504030201);
-  assert.equal(buf.readIntBE(0, 5), 0x0102030405);
-  assert.equal(buf.readIntLE(0, 6), 0x060504030201);
-  assert.equal(buf.readIntBE(0, 6), 0x010203040506);
-})();
+{
+  const buf = new Buffer([0x01, 0x02, 0x03, 0x04, 0x05, 0x06]);
+
+  assert.strictEqual(buf.readUIntLE(0, 1), 0x01);
+  assert.strictEqual(buf.readUIntBE(0, 1), 0x01);
+  assert.strictEqual(buf.readUIntLE(0, 3), 0x030201);
+  assert.strictEqual(buf.readUIntBE(0, 3), 0x010203);
+  assert.strictEqual(buf.readUIntLE(0, 5), 0x0504030201);
+  assert.strictEqual(buf.readUIntBE(0, 5), 0x0102030405);
+  assert.strictEqual(buf.readUIntLE(0, 6), 0x060504030201);
+  assert.strictEqual(buf.readUIntBE(0, 6), 0x010203040506);
+  assert.strictEqual(buf.readIntLE(0, 1), 0x01);
+  assert.strictEqual(buf.readIntBE(0, 1), 0x01);
+  assert.strictEqual(buf.readIntLE(0, 3), 0x030201);
+  assert.strictEqual(buf.readIntBE(0, 3), 0x010203);
+  assert.strictEqual(buf.readIntLE(0, 5), 0x0504030201);
+  assert.strictEqual(buf.readIntBE(0, 5), 0x0102030405);
+  assert.strictEqual(buf.readIntLE(0, 6), 0x060504030201);
+  assert.strictEqual(buf.readIntBE(0, 6), 0x010203040506);
+}
 
 // test for common write(U)IntLE/BE
-(function() {
-  var buf = Buffer(3);
+{
+  let buf = Buffer(3);
   buf.writeUIntLE(0x123456, 0, 3);
   assert.deepStrictEqual(buf.toJSON().data, [0x56, 0x34, 0x12]);
   assert.equal(buf.readUIntLE(0, 3), 0x123456);
@@ -1303,11 +1303,11 @@ assert.throws(function() {
   buf.writeIntBE(-0x0012000000, 0, 5);
   assert.deepStrictEqual(buf.toJSON().data, [0xff, 0xee, 0x00, 0x00, 0x00]);
   assert.equal(buf.readIntBE(0, 5), -0x0012000000);
-})();
+}
 
 // test Buffer slice
-(function() {
-  var buf = new Buffer('0123456789');
+{
+  const buf = new Buffer('0123456789');
   assert.equal(buf.slice(-10, 10), '0123456789');
   assert.equal(buf.slice(-20, 10), '0123456789');
   assert.equal(buf.slice(-20, -10), '');
@@ -1340,7 +1340,7 @@ assert.throws(function() {
     assert.equal(buf.slice(0, -i), s.slice(0, -i));
   }
 
-  var utf16Buf = new Buffer('0123456789', 'utf16le');
+  const utf16Buf = new Buffer('0123456789', 'utf16le');
   assert.deepStrictEqual(utf16Buf.slice(0, 6), Buffer('012', 'utf16le'));
 
   assert.equal(buf.slice('0', '1'), '0');
@@ -1354,7 +1354,7 @@ assert.throws(function() {
   // try to slice a zero length Buffer
   // see https://github.com/joyent/node/issues/5881
   SlowBuffer(0).slice(0, 1);
-})();
+}
 
 // Regression test for #5482: should throw but not assert in C++ land.
 assert.throws(function() {
@@ -1363,20 +1363,20 @@ assert.throws(function() {
 
 // Regression test for #6111. Constructing a buffer from another buffer
 // should a) work, and b) not corrupt the source buffer.
-(function() {
-  var a = [0];
+{
+  let a = [0];
   for (let i = 0; i < 7; ++i) a = a.concat(a);
   a = a.map(function(_, i) { return i; });
   const b = Buffer(a);
   const c = Buffer(b);
-  assert.equal(b.length, a.length);
-  assert.equal(c.length, a.length);
+  assert.strictEqual(b.length, a.length);
+  assert.strictEqual(c.length, a.length);
   for (let i = 0, k = a.length; i < k; ++i) {
-    assert.equal(a[i], i);
-    assert.equal(b[i], i);
-    assert.equal(c[i], i);
+    assert.strictEqual(a[i], i);
+    assert.strictEqual(b[i], i);
+    assert.strictEqual(c[i], i);
   }
-})();
+}
 
 
 assert.throws(function() {
diff --git a/test/parallel/test-child-process-cwd.js b/test/parallel/test-child-process-cwd.js
index 108538629e..acba57939f 100644
--- a/test/parallel/test-child-process-cwd.js
+++ b/test/parallel/test-child-process-cwd.js
@@ -44,18 +44,11 @@ if (common.isWindows) {
 }
 
 // Assume does-not-exist doesn't exist, expect exitCode=-1 and errno=ENOENT
-(function() {
-  var errors = 0;
-
-  testCwd({cwd: 'does-not-exist'}, -1).on('error', function(e) {
+{
+  testCwd({cwd: 'does-not-exist'}, -1).on('error', common.mustCall(function(e) {
     assert.equal(e.code, 'ENOENT');
-    errors++;
-  });
-
-  process.on('exit', function() {
-    assert.equal(errors, 1);
-  });
-})();
+  }));
+}
 
 // Spawn() shouldn't try to chdir() so this should just work
 testCwd(undefined, 0);
diff --git a/test/parallel/test-crypto-authenticated.js b/test/parallel/test-crypto-authenticated.js
index f1b92f8a19..331c2d20e0 100644
--- a/test/parallel/test-crypto-authenticated.js
+++ b/test/parallel/test-crypto-authenticated.js
@@ -322,34 +322,34 @@ for (var i in TEST_CASES) {
     continue;
   }
 
-  (function() {
-    var encrypt = crypto.createCipheriv(test.algo,
+  {
+    const encrypt = crypto.createCipheriv(test.algo,
       Buffer.from(test.key, 'hex'), Buffer.from(test.iv, 'hex'));
     if (test.aad)
       encrypt.setAAD(Buffer.from(test.aad, 'hex'));
 
-    var inputEncoding = test.plainIsHex ? 'hex' : 'ascii';
-    var hex = encrypt.update(test.plain, inputEncoding, 'hex');
+    const inputEncoding = test.plainIsHex ? 'hex' : 'ascii';
+    let hex = encrypt.update(test.plain, inputEncoding, 'hex');
     hex += encrypt.final('hex');
 
-    var auth_tag = encrypt.getAuthTag();
+    const auth_tag = encrypt.getAuthTag();
     // only test basic encryption run if output is marked as tampered.
     if (!test.tampered) {
-      assert.equal(hex, test.ct);
-      assert.equal(auth_tag.toString('hex'), test.tag);
+      assert.strictEqual(hex, test.ct);
+      assert.strictEqual(auth_tag.toString('hex'), test.tag);
     }
-  })();
+  }
 
-  (function() {
-    var decrypt = crypto.createDecipheriv(test.algo,
+  {
+    const decrypt = crypto.createDecipheriv(test.algo,
       Buffer.from(test.key, 'hex'), Buffer.from(test.iv, 'hex'));
     decrypt.setAuthTag(Buffer.from(test.tag, 'hex'));
     if (test.aad)
       decrypt.setAAD(Buffer.from(test.aad, 'hex'));
 
-    var outputEncoding = test.plainIsHex ? 'hex' : 'ascii';
+    const outputEncoding = test.plainIsHex ? 'hex' : 'ascii';
 
-    var msg = decrypt.update(test.ct, 'hex', outputEncoding);
+    let msg = decrypt.update(test.ct, 'hex', outputEncoding);
     if (!test.tampered) {
       msg += decrypt.final(outputEncoding);
       assert.equal(msg, test.plain);
@@ -357,48 +357,48 @@ for (var i in TEST_CASES) {
       // assert that final throws if input data could not be verified!
       assert.throws(function() { decrypt.final('ascii'); }, / auth/);
     }
-  })();
+  }
 
-  (function() {
+  {
     if (!test.password) return;
     if (common.hasFipsCrypto) {
       assert.throws(() => { crypto.createCipher(test.algo, test.password); },
                     /not supported in FIPS mode/);
     } else {
-      var encrypt = crypto.createCipher(test.algo, test.password);
+      const encrypt = crypto.createCipher(test.algo, test.password);
       if (test.aad)
         encrypt.setAAD(Buffer.from(test.aad, 'hex'));
-      var hex = encrypt.update(test.plain, 'ascii', 'hex');
+      let hex = encrypt.update(test.plain, 'ascii', 'hex');
       hex += encrypt.final('hex');
-      var auth_tag = encrypt.getAuthTag();
+      const auth_tag = encrypt.getAuthTag();
       // only test basic encryption run if output is marked as tampered.
       if (!test.tampered) {
-        assert.equal(hex, test.ct);
-        assert.equal(auth_tag.toString('hex'), test.tag);
+        assert.strictEqual(hex, test.ct);
+        assert.strictEqual(auth_tag.toString('hex'), test.tag);
       }
     }
-  })();
+  }
 
-  (function() {
+  {
     if (!test.password) return;
     if (common.hasFipsCrypto) {
       assert.throws(() => { crypto.createDecipher(test.algo, test.password); },
                     /not supported in FIPS mode/);
     } else {
-      var decrypt = crypto.createDecipher(test.algo, test.password);
+      const decrypt = crypto.createDecipher(test.algo, test.password);
       decrypt.setAuthTag(Buffer.from(test.tag, 'hex'));
       if (test.aad)
         decrypt.setAAD(Buffer.from(test.aad, 'hex'));
-      var msg = decrypt.update(test.ct, 'hex', 'ascii');
+      let msg = decrypt.update(test.ct, 'hex', 'ascii');
       if (!test.tampered) {
         msg += decrypt.final('ascii');
-        assert.equal(msg, test.plain);
+        assert.strictEqual(msg, test.plain);
       } else {
         // assert that final throws if input data could not be verified!
         assert.throws(function() { decrypt.final('ascii'); }, / auth/);
       }
     }
-  })();
+  }
 
   // after normal operation, test some incorrect ways of calling the API:
   // it's most certainly enough to run these tests with one algorithm only.
@@ -407,41 +407,41 @@ for (var i in TEST_CASES) {
     continue;
   }
 
-  (function() {
+  {
     // non-authenticating mode:
-    var encrypt = crypto.createCipheriv('aes-128-cbc',
+    const encrypt = crypto.createCipheriv('aes-128-cbc',
       'ipxp9a6i1Mb4USb4', '6fKjEjR3Vl30EUYC');
     encrypt.update('blah', 'ascii');
     encrypt.final();
     assert.throws(() => { encrypt.getAuthTag(); }, / state/);
     assert.throws(() => { encrypt.setAAD(Buffer.from('123', 'ascii')); },
                   / state/);
-  })();
+  }
 
-  (function() {
+  {
     // trying to get tag before inputting all data:
-    var encrypt = crypto.createCipheriv(test.algo,
+    const encrypt = crypto.createCipheriv(test.algo,
       Buffer.from(test.key, 'hex'), Buffer.from(test.iv, 'hex'));
     encrypt.update('blah', 'ascii');
     assert.throws(function() { encrypt.getAuthTag(); }, / state/);
-  })();
+  }
 
-  (function() {
+  {
     // trying to set tag on encryption object:
-    var encrypt = crypto.createCipheriv(test.algo,
+    const encrypt = crypto.createCipheriv(test.algo,
       Buffer.from(test.key, 'hex'), Buffer.from(test.iv, 'hex'));
     assert.throws(() => { encrypt.setAuthTag(Buffer.from(test.tag, 'hex')); },
                   / state/);
-  })();
+  }
 
-  (function() {
+  {
     // trying to read tag from decryption object:
-    var decrypt = crypto.createDecipheriv(test.algo,
+    const decrypt = crypto.createDecipheriv(test.algo,
       Buffer.from(test.key, 'hex'), Buffer.from(test.iv, 'hex'));
     assert.throws(function() { decrypt.getAuthTag(); }, / state/);
-  })();
+  }
 
-  (function() {
+  {
     // trying to create cipher with incorrect IV length
     assert.throws(function() {
       crypto.createCipheriv(
@@ -450,5 +450,5 @@ for (var i in TEST_CASES) {
         Buffer.alloc(0)
       );
     }, /Invalid IV length/);
-  })();
+  }
 }
diff --git a/test/parallel/test-crypto-binary-default.js b/test/parallel/test-crypto-binary-default.js
index bca8e13dd5..e163c9e4cd 100644
--- a/test/parallel/test-crypto-binary-default.js
+++ b/test/parallel/test-crypto-binary-default.js
@@ -580,58 +580,58 @@ assert.strictEqual(rsaVerify.verify(rsaPubPem, rsaSignature, 'hex'), true);
 //
 // Test RSA signing and verification
 //
-(function() {
-  var privateKey = fs.readFileSync(
+{
+  const privateKey = fs.readFileSync(
       common.fixturesDir + '/test_rsa_privkey_2.pem');
 
-  var publicKey = fs.readFileSync(
+  const publicKey = fs.readFileSync(
       common.fixturesDir + '/test_rsa_pubkey_2.pem');
 
-  var input = 'I AM THE WALRUS';
+  const input = 'I AM THE WALRUS';
 
-  var signature =
+  const signature =
       '79d59d34f56d0e94aa6a3e306882b52ed4191f07521f25f505a078dc2f89' +
       '396e0c8ac89e996fde5717f4cb89199d8fec249961fcb07b74cd3d2a4ffa' +
       '235417b69618e4bcd76b97e29975b7ce862299410e1b522a328e44ac9bb2' +
       '8195e0268da7eda23d9825ac43c724e86ceeee0d0d4465678652ccaf6501' +
       '0ddfb299bedeb1ad';
 
-  var sign = crypto.createSign('RSA-SHA256');
+  const sign = crypto.createSign('RSA-SHA256');
   sign.update(input);
 
-  var output = sign.sign(privateKey, 'hex');
-  assert.equal(output, signature);
+  const output = sign.sign(privateKey, 'hex');
+  assert.strictEqual(output, signature);
 
-  var verify = crypto.createVerify('RSA-SHA256');
+  const verify = crypto.createVerify('RSA-SHA256');
   verify.update(input);
 
   assert.strictEqual(verify.verify(publicKey, signature, 'hex'), true);
-})();
+}
 
 
 //
 // Test DSA signing and verification
 //
-(function() {
-  var privateKey = fs.readFileSync(
+{
+  const privateKey = fs.readFileSync(
       common.fixturesDir + '/test_dsa_privkey.pem');
 
-  var publicKey = fs.readFileSync(
+  const publicKey = fs.readFileSync(
       common.fixturesDir + '/test_dsa_pubkey.pem');
 
-  var input = 'I AM THE WALRUS';
+  const input = 'I AM THE WALRUS';
 
   // DSA signatures vary across runs so there is no static string to verify
   // against
-  var sign = crypto.createSign('DSS1');
+  const sign = crypto.createSign('DSS1');
   sign.update(input);
-  var signature = sign.sign(privateKey, 'hex');
+  const signature = sign.sign(privateKey, 'hex');
 
-  var verify = crypto.createVerify('DSS1');
+  const verify = crypto.createVerify('DSS1');
   verify.update(input);
 
   assert.strictEqual(verify.verify(publicKey, signature, 'hex'), true);
-})();
+}
 
 
 //
diff --git a/test/parallel/test-crypto-cipher-decipher.js b/test/parallel/test-crypto-cipher-decipher.js
index eef329b5f3..8c9daa16e8 100644
--- a/test/parallel/test-crypto-cipher-decipher.js
+++ b/test/parallel/test-crypto-cipher-decipher.js
@@ -73,35 +73,35 @@ testCipher2('0123456789abcdef');
 testCipher2(Buffer.from('0123456789abcdef'));
 
 // Base64 padding regression test, see #4837.
-(function() {
-  var c = crypto.createCipher('aes-256-cbc', 'secret');
-  var s = c.update('test', 'utf8', 'base64') + c.final('base64');
-  assert.equal(s, '375oxUQCIocvxmC5At+rvA==');
-})();
+{
+  const c = crypto.createCipher('aes-256-cbc', 'secret');
+  const s = c.update('test', 'utf8', 'base64') + c.final('base64');
+  assert.strictEqual(s, '375oxUQCIocvxmC5At+rvA==');
+}
 
 // Calling Cipher.final() or Decipher.final() twice should error but
 // not assert. See #4886.
-(function() {
-  var c = crypto.createCipher('aes-256-cbc', 'secret');
+{
+  const c = crypto.createCipher('aes-256-cbc', 'secret');
   try { c.final('xxx'); } catch (e) { /* Ignore. */ }
   try { c.final('xxx'); } catch (e) { /* Ignore. */ }
   try { c.final('xxx'); } catch (e) { /* Ignore. */ }
-  var d = crypto.createDecipher('aes-256-cbc', 'secret');
+  const d = crypto.createDecipher('aes-256-cbc', 'secret');
   try { d.final('xxx'); } catch (e) { /* Ignore. */ }
   try { d.final('xxx'); } catch (e) { /* Ignore. */ }
   try { d.final('xxx'); } catch (e) { /* Ignore. */ }
-})();
+}
 
 // Regression test for #5482: string to Cipher#update() should not assert.
-(function() {
-  var c = crypto.createCipher('aes192', '0123456789abcdef');
+{
+  const c = crypto.createCipher('aes192', '0123456789abcdef');
   c.update('update');
   c.final();
-})();
+}
 
 // #5655 regression tests, 'utf-8' and 'utf8' are identical.
-(function() {
-  var c = crypto.createCipher('aes192', '0123456789abcdef');
+{
+  let c = crypto.createCipher('aes192', '0123456789abcdef');
   c.update('update', '');  // Defaults to "utf8".
   c.final('utf-8');  // Should not throw.
 
@@ -112,4 +112,4 @@ testCipher2(Buffer.from('0123456789abcdef'));
   c = crypto.createCipher('aes192', '0123456789abcdef');
   c.update('update', 'utf-8');
   c.final('utf8');  // Should not throw.
-})();
+}
diff --git a/test/parallel/test-crypto-dh.js b/test/parallel/test-crypto-dh.js
index 9d383ed417..6a067bef1b 100644
--- a/test/parallel/test-crypto-dh.js
+++ b/test/parallel/test-crypto-dh.js
@@ -57,19 +57,19 @@ var secret3 = dh3.computeSecret(key2, 'hex', 'base64');
 assert.equal(secret1, secret3);
 
 // Run this one twice to make sure that the dh3 clears its error properly
-(function() {
-  var c = crypto.createDecipheriv('aes-128-ecb', crypto.randomBytes(16), '');
+{
+  const c = crypto.createDecipheriv('aes-128-ecb', crypto.randomBytes(16), '');
   assert.throws(function() { c.final('utf8'); }, /wrong final block length/);
-})();
+}
 
 assert.throws(function() {
   dh3.computeSecret('');
 }, /key is too small/i);
 
-(function() {
-  var c = crypto.createDecipheriv('aes-128-ecb', crypto.randomBytes(16), '');
+{
+  const c = crypto.createDecipheriv('aes-128-ecb', crypto.randomBytes(16), '');
   assert.throws(function() { c.final('utf8'); }, /wrong final block length/);
-})();
+}
 
 // Create a shared using a DH group.
 var alice = crypto.createDiffieHellmanGroup('modp5');
diff --git a/test/parallel/test-crypto-from-binary.js b/test/parallel/test-crypto-from-binary.js
index 5c7e75a721..0889541ef6 100644
--- a/test/parallel/test-crypto-from-binary.js
+++ b/test/parallel/test-crypto-from-binary.js
@@ -29,18 +29,18 @@ var b = Buffer.from(ucs2_control + ucs2_control, 'ucs2');
 //
 // Test updating from birant data
 //
-(function() {
-  var datum1 = b.slice(700000);
-  var hash1_converted = crypto.createHash('sha1')
+{
+  const datum1 = b.slice(700000);
+  const hash1_converted = crypto.createHash('sha1')
     .update(datum1.toString('base64'), 'base64')
     .digest('hex');
-  var hash1_direct = crypto.createHash('sha1').update(datum1).digest('hex');
-  assert.equal(hash1_direct, hash1_converted, 'should hash the same.');
+  const hash1_direct = crypto.createHash('sha1').update(datum1).digest('hex');
+  assert.strictEqual(hash1_direct, hash1_converted, 'should hash the same.');
 
-  var datum2 = b;
-  var hash2_converted = crypto.createHash('sha1')
+  const datum2 = b;
+  const hash2_converted = crypto.createHash('sha1')
     .update(datum2.toString('base64'), 'base64')
     .digest('hex');
-  var hash2_direct = crypto.createHash('sha1').update(datum2).digest('hex');
-  assert.equal(hash2_direct, hash2_converted, 'should hash the same.');
-})();
+  const hash2_direct = crypto.createHash('sha1').update(datum2).digest('hex');
+  assert.strictEqual(hash2_direct, hash2_converted, 'should hash the same.');
+}
diff --git a/test/parallel/test-crypto-rsa-dsa.js b/test/parallel/test-crypto-rsa-dsa.js
index 15b56c642b..396717ef74 100644
--- a/test/parallel/test-crypto-rsa-dsa.js
+++ b/test/parallel/test-crypto-rsa-dsa.js
@@ -27,20 +27,20 @@ var dsaKeyPemEncrypted = fs.readFileSync(
   common.fixturesDir + '/test_dsa_privkey_encrypted.pem', 'ascii');
 
 // Test RSA encryption/decryption
-(function() {
-  var input = 'I AM THE WALRUS';
-  var bufferToEncrypt = Buffer.from(input);
+{
+  const input = 'I AM THE WALRUS';
+  const bufferToEncrypt = Buffer.from(input);
 
-  var encryptedBuffer = crypto.publicEncrypt(rsaPubPem, bufferToEncrypt);
+  let encryptedBuffer = crypto.publicEncrypt(rsaPubPem, bufferToEncrypt);
 
-  var decryptedBuffer = crypto.privateDecrypt(rsaKeyPem, encryptedBuffer);
-  assert.equal(input, decryptedBuffer.toString());
+  let decryptedBuffer = crypto.privateDecrypt(rsaKeyPem, encryptedBuffer);
+  assert.strictEqual(input, decryptedBuffer.toString());
 
-  var decryptedBufferWithPassword = crypto.privateDecrypt({
+  let decryptedBufferWithPassword = crypto.privateDecrypt({
     key: rsaKeyPemEncrypted,
     passphrase: 'password'
   }, encryptedBuffer);
-  assert.equal(input, decryptedBufferWithPassword.toString());
+  assert.strictEqual(input, decryptedBufferWithPassword.toString());
 
   encryptedBuffer = crypto.publicEncrypt({
     key: rsaKeyPemEncrypted,
@@ -51,7 +51,7 @@ var dsaKeyPemEncrypted = fs.readFileSync(
     key: rsaKeyPemEncrypted,
     passphrase: 'password'
   }, encryptedBuffer);
-  assert.equal(input, decryptedBufferWithPassword.toString());
+  assert.strictEqual(input, decryptedBufferWithPassword.toString());
 
   encryptedBuffer = crypto.privateEncrypt({
     key: rsaKeyPemEncrypted,
@@ -62,22 +62,22 @@ var dsaKeyPemEncrypted = fs.readFileSync(
     key: rsaKeyPemEncrypted,
     passphrase: Buffer.from('password')
   }, encryptedBuffer);
-  assert.equal(input, decryptedBufferWithPassword.toString());
+  assert.strictEqual(input, decryptedBufferWithPassword.toString());
 
   encryptedBuffer = crypto.publicEncrypt(certPem, bufferToEncrypt);
 
   decryptedBuffer = crypto.privateDecrypt(keyPem, encryptedBuffer);
-  assert.equal(input, decryptedBuffer.toString());
+  assert.strictEqual(input, decryptedBuffer.toString());
 
   encryptedBuffer = crypto.publicEncrypt(keyPem, bufferToEncrypt);
 
   decryptedBuffer = crypto.privateDecrypt(keyPem, encryptedBuffer);
-  assert.equal(input, decryptedBuffer.toString());
+  assert.strictEqual(input, decryptedBuffer.toString());
 
   encryptedBuffer = crypto.privateEncrypt(keyPem, bufferToEncrypt);
 
   decryptedBuffer = crypto.publicDecrypt(keyPem, encryptedBuffer);
-  assert.equal(input, decryptedBuffer.toString());
+  assert.strictEqual(input, decryptedBuffer.toString());
 
   assert.throws(function() {
     crypto.privateDecrypt({
@@ -104,7 +104,7 @@ var dsaKeyPemEncrypted = fs.readFileSync(
       passphrase: [].concat.apply([], Buffer.from('password'))
     }, encryptedBuffer);
   });
-})();
+}
 
 function test_rsa(padding) {
   var input = Buffer.allocUnsafe(padding === 'RSA_NO_PADDING' ? 1024 / 8 : 32);
@@ -176,52 +176,52 @@ assert.throws(function() {
 //
 // Test RSA signing and verification
 //
-(function() {
-  var privateKey = fs.readFileSync(
+{
+  const privateKey = fs.readFileSync(
       common.fixturesDir + '/test_rsa_privkey_2.pem');
 
-  var publicKey = fs.readFileSync(
+  const publicKey = fs.readFileSync(
       common.fixturesDir + '/test_rsa_pubkey_2.pem');
 
-  var input = 'I AM THE WALRUS';
+  const input = 'I AM THE WALRUS';
 
-  var signature =
+  const signature =
       '79d59d34f56d0e94aa6a3e306882b52ed4191f07521f25f505a078dc2f89' +
       '396e0c8ac89e996fde5717f4cb89199d8fec249961fcb07b74cd3d2a4ffa' +
       '235417b69618e4bcd76b97e29975b7ce862299410e1b522a328e44ac9bb2' +
       '8195e0268da7eda23d9825ac43c724e86ceeee0d0d4465678652ccaf6501' +
       '0ddfb299bedeb1ad';
 
-  var sign = crypto.createSign('RSA-SHA256');
+  const sign = crypto.createSign('RSA-SHA256');
   sign.update(input);
 
-  var output = sign.sign(privateKey, 'hex');
-  assert.equal(output, signature);
+  const output = sign.sign(privateKey, 'hex');
+  assert.strictEqual(output, signature);
 
-  var verify = crypto.createVerify('RSA-SHA256');
+  const verify = crypto.createVerify('RSA-SHA256');
   verify.update(input);
 
   assert.strictEqual(verify.verify(publicKey, signature, 'hex'), true);
-})();
+}
 
 
 //
 // Test DSA signing and verification
 //
-(function() {
-  var input = 'I AM THE WALRUS';
+{
+  const input = 'I AM THE WALRUS';
 
   // DSA signatures vary across runs so there is no static string to verify
   // against
-  var sign = crypto.createSign('DSS1');
+  const sign = crypto.createSign('DSS1');
   sign.update(input);
-  var signature = sign.sign(dsaKeyPem, 'hex');
+  const signature = sign.sign(dsaKeyPem, 'hex');
 
-  var verify = crypto.createVerify('DSS1');
+  const verify = crypto.createVerify('DSS1');
   verify.update(input);
 
   assert.strictEqual(verify.verify(dsaPubPem, signature, 'hex'), true);
-})();
+}
 
 
 //
diff --git a/test/parallel/test-fs-mkdir.js b/test/parallel/test-fs-mkdir.js
index ae13b9bc7a..2b8e8b8f02 100644
--- a/test/parallel/test-fs-mkdir.js
+++ b/test/parallel/test-fs-mkdir.js
@@ -12,53 +12,47 @@ function unlink(pathname) {
 
 common.refreshTmpDir();
 
-(function() {
-  var ncalls = 0;
-  var pathname = common.tmpDir + '/test1';
+{
+  const pathname = common.tmpDir + '/test1';
 
   unlink(pathname);
 
-  fs.mkdir(pathname, function(err) {
-    assert.equal(err, null);
-    assert.equal(common.fileExists(pathname), true);
-    ncalls++;
-  });
+  fs.mkdir(pathname, common.mustCall(function(err) {
+    assert.strictEqual(err, null);
+    assert.strictEqual(common.fileExists(pathname), true);
+  }));
 
   process.on('exit', function() {
     unlink(pathname);
-    assert.equal(ncalls, 1);
   });
-})();
+}
 
-(function() {
-  var ncalls = 0;
-  var pathname = common.tmpDir + '/test2';
+{
+  const pathname = common.tmpDir + '/test2';
 
   unlink(pathname);
 
-  fs.mkdir(pathname, 0o777, function(err) {
+  fs.mkdir(pathname, 0o777, common.mustCall(function(err) {
     assert.equal(err, null);
     assert.equal(common.fileExists(pathname), true);
-    ncalls++;
-  });
+  }));
 
   process.on('exit', function() {
     unlink(pathname);
-    assert.equal(ncalls, 1);
   });
-})();
+}
 
-(function() {
-  var pathname = common.tmpDir + '/test3';
+{
+  const pathname = common.tmpDir + '/test3';
 
   unlink(pathname);
   fs.mkdirSync(pathname);
 
-  var exists = common.fileExists(pathname);
+  const exists = common.fileExists(pathname);
   unlink(pathname);
 
-  assert.equal(exists, true);
-})();
+  assert.strictEqual(exists, true);
+}
 
 // Keep the event loop alive so the async mkdir() requests
 // have a chance to run (since they don't ref the event loop).
diff --git a/test/parallel/test-fs-truncate-GH-6233.js b/test/parallel/test-fs-truncate-GH-6233.js
index 023d08b151..acfdd1ccae 100644
--- a/test/parallel/test-fs-truncate-GH-6233.js
+++ b/test/parallel/test-fs-truncate-GH-6233.js
@@ -8,19 +8,19 @@ var filename = common.tmpDir + '/truncate-file.txt';
 common.refreshTmpDir();
 
 // Synchronous test.
-(function() {
+{
   fs.writeFileSync(filename, '0123456789');
-  assert.equal(fs.readFileSync(filename).toString(), '0123456789');
+  assert.strictEqual(fs.readFileSync(filename).toString(), '0123456789');
   fs.truncateSync(filename, 5);
-  assert.equal(fs.readFileSync(filename).toString(), '01234');
-})();
+  assert.strictEqual(fs.readFileSync(filename).toString(), '01234');
+}
 
 // Asynchronous test.
-(function() {
+{
   fs.writeFileSync(filename, '0123456789');
-  assert.equal(fs.readFileSync(filename).toString(), '0123456789');
+  assert.strictEqual(fs.readFileSync(filename).toString(), '0123456789');
   fs.truncate(filename, 5, common.mustCall(function(err) {
-    if (err) throw err;
-    assert.equal(fs.readFileSync(filename).toString(), '01234');
+    assert.ifError(err);
+    assert.strictEqual(fs.readFileSync(filename).toString(), '01234');
   }));
-})();
+}
diff --git a/test/parallel/test-fs-write-stream-end.js b/test/parallel/test-fs-write-stream-end.js
index a8af29d132..ade6777d5f 100644
--- a/test/parallel/test-fs-write-stream-end.js
+++ b/test/parallel/test-fs-write-stream-end.js
@@ -6,19 +6,19 @@ var fs = require('fs');
 
 common.refreshTmpDir();
 
-(function() {
-  var file = path.join(common.tmpDir, 'write-end-test0.txt');
-  var stream = fs.createWriteStream(file);
+{
+  const file = path.join(common.tmpDir, 'write-end-test0.txt');
+  const stream = fs.createWriteStream(file);
   stream.end();
   stream.on('close', common.mustCall(function() { }));
-})();
+}
 
-(function() {
-  var file = path.join(common.tmpDir, 'write-end-test1.txt');
-  var stream = fs.createWriteStream(file);
+{
+  const file = path.join(common.tmpDir, 'write-end-test1.txt');
+  const stream = fs.createWriteStream(file);
   stream.end('a\n', 'utf8');
   stream.on('close', common.mustCall(function() {
-    var content = fs.readFileSync(file, 'utf8');
-    assert.equal(content, 'a\n');
+    const content = fs.readFileSync(file, 'utf8');
+    assert.strictEqual(content, 'a\n');
   }));
-})();
+}
diff --git a/test/parallel/test-fs-write-stream.js b/test/parallel/test-fs-write-stream.js
index 5d29e60545..71aaaa75dd 100644
--- a/test/parallel/test-fs-write-stream.js
+++ b/test/parallel/test-fs-write-stream.js
@@ -8,7 +8,7 @@ var file = path.join(common.tmpDir, 'write.txt');
 
 common.refreshTmpDir();
 
-(function() {
+{
   const stream = fs.WriteStream(file);
   const _fs_close = fs.close;
 
@@ -17,15 +17,14 @@ common.refreshTmpDir();
     fs.close = _fs_close;
   };
   stream.destroy();
-})();
+}
 
-(function() {
-  var stream = fs.createWriteStream(file);
+{
+  const stream = fs.createWriteStream(file);
 
   stream.on('drain', function() {
-    assert.fail(null, null, '\'drain\' event must not be emitted before ' +
+    common.fail('\'drain\' event must not be emitted before ' +
                 'stream.write() has been called at least once.');
   });
   stream.destroy();
-})();
-
+}
diff --git a/test/parallel/test-http-1.0.js b/test/parallel/test-http-1.0.js
index 622dd4a16f..d01613de45 100644
--- a/test/parallel/test-http-1.0.js
+++ b/test/parallel/test-http-1.0.js
@@ -35,11 +35,11 @@ function test(handler, request_generator, response_validator) {
   });
 }
 
-(function() {
+{
   function handler(req, res) {
-    assert.equal('1.0', req.httpVersion);
-    assert.equal(1, req.httpVersionMajor);
-    assert.equal(0, req.httpVersionMinor);
+    assert.strictEqual('1.0', req.httpVersion);
+    assert.strictEqual(1, req.httpVersionMajor);
+    assert.strictEqual(0, req.httpVersionMinor);
     res.writeHead(200, {'Content-Type': 'text/plain'});
     res.end(body);
   }
@@ -49,25 +49,25 @@ function test(handler, request_generator, response_validator) {
   }
 
   function response_validator(server_response, client_got_eof, timed_out) {
-    var m = server_response.split('\r\n\r\n');
-    assert.equal(m[1], body);
-    assert.equal(true, client_got_eof);
-    assert.equal(false, timed_out);
+    const m = server_response.split('\r\n\r\n');
+    assert.strictEqual(m[1], body);
+    assert.strictEqual(true, client_got_eof);
+    assert.strictEqual(false, timed_out);
   }
 
   test(handler, request_generator, response_validator);
-})();
+}
 
 //
 // Don't send HTTP/1.1 status lines to HTTP/1.0 clients.
 //
 // https://github.com/joyent/node/issues/1234
 //
-(function() {
+{
   function handler(req, res) {
-    assert.equal('1.0', req.httpVersion);
-    assert.equal(1, req.httpVersionMajor);
-    assert.equal(0, req.httpVersionMinor);
+    assert.strictEqual('1.0', req.httpVersion);
+    assert.strictEqual(1, req.httpVersionMajor);
+    assert.strictEqual(0, req.httpVersionMinor);
     res.sendDate = false;
     res.writeHead(200, {'Content-Type': 'text/plain'});
     res.write('Hello, '); res._send('');
@@ -85,25 +85,25 @@ function test(handler, request_generator, response_validator) {
   }
 
   function response_validator(server_response, client_got_eof, timed_out) {
-    var expected_response = 'HTTP/1.1 200 OK\r\n' +
-                            'Content-Type: text/plain\r\n' +
-                            'Connection: close\r\n' +
-                            '\r\n' +
-                            'Hello, world!';
-
-    assert.equal(expected_response, server_response);
-    assert.equal(true, client_got_eof);
-    assert.equal(false, timed_out);
+    const expected_response = 'HTTP/1.1 200 OK\r\n' +
+                              'Content-Type: text/plain\r\n' +
+                              'Connection: close\r\n' +
+                              '\r\n' +
+                              'Hello, world!';
+
+    assert.strictEqual(expected_response, server_response);
+    assert.strictEqual(true, client_got_eof);
+    assert.strictEqual(false, timed_out);
   }
 
   test(handler, request_generator, response_validator);
-})();
+}
 
-(function() {
+{
   function handler(req, res) {
-    assert.equal('1.1', req.httpVersion);
-    assert.equal(1, req.httpVersionMajor);
-    assert.equal(1, req.httpVersionMinor);
+    assert.strictEqual('1.1', req.httpVersion);
+    assert.strictEqual(1, req.httpVersionMajor);
+    assert.strictEqual(1, req.httpVersionMinor);
     res.sendDate = false;
     res.writeHead(200, {'Content-Type': 'text/plain'});
     res.write('Hello, '); res._send('');
@@ -112,32 +112,32 @@ function test(handler, request_generator, response_validator) {
   }
 
   function request_generator() {
-    return ('GET / HTTP/1.1\r\n' +
+    return 'GET / HTTP/1.1\r\n' +
         'User-Agent: curl/7.19.7 (x86_64-pc-linux-gnu) libcurl/7.19.7 ' +
         'OpenSSL/0.9.8k zlib/1.2.3.3 libidn/1.15\r\n' +
         'Connection: close\r\n' +
         'Host: 127.0.0.1:1337\r\n' +
         'Accept: */*\r\n' +
-        '\r\n');
+        '\r\n';
   }
 
   function response_validator(server_response, client_got_eof, timed_out) {
-    var expected_response = 'HTTP/1.1 200 OK\r\n' +
-                            'Content-Type: text/plain\r\n' +
-                            'Connection: close\r\n' +
-                            'Transfer-Encoding: chunked\r\n' +
-                            '\r\n' +
-                            '7\r\n' +
-                            'Hello, \r\n' +
-                            '6\r\n' +
-                            'world!\r\n' +
-                            '0\r\n' +
-                            '\r\n';
-
-    assert.equal(expected_response, server_response);
-    assert.equal(true, client_got_eof);
-    assert.equal(false, timed_out);
+    const expected_response = 'HTTP/1.1 200 OK\r\n' +
+                              'Content-Type: text/plain\r\n' +
+                              'Connection: close\r\n' +
+                              'Transfer-Encoding: chunked\r\n' +
+                              '\r\n' +
+                              '7\r\n' +
+                              'Hello, \r\n' +
+                              '6\r\n' +
+                              'world!\r\n' +
+                              '0\r\n' +
+                              '\r\n';
+
+    assert.strictEqual(expected_response, server_response);
+    assert.strictEqual(true, client_got_eof);
+    assert.strictEqual(false, timed_out);
   }
 
   test(handler, request_generator, response_validator);
-})();
+}
diff --git a/test/parallel/test-http-parser.js b/test/parallel/test-http-parser.js
index 360dc6ccc9..abc1d096df 100644
--- a/test/parallel/test-http-parser.js
+++ b/test/parallel/test-http-parser.js
@@ -72,21 +72,21 @@ function expectBody(expected) {
 //
 // Simple request test.
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'GET /hello HTTP/1.1' + CRLF +
       CRLF);
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 1);
-    assert.equal(method, methods.indexOf('GET'));
-    assert.equal(url || parser.url, '/hello');
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 1);
+    assert.strictEqual(method, methods.indexOf('GET'));
+    assert.strictEqual(url || parser.url, '/hello');
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser.execute(request, 0, request.length);
 
@@ -104,72 +104,72 @@ function expectBody(expected) {
   assert.throws(function() {
     parser.execute(request, 0, request.length);
   }, Error, 'hello world');
-})();
+}
 
 
 //
 // Simple response test.
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'HTTP/1.1 200 OK' + CRLF +
       'Content-Type: text/plain' + CRLF +
       'Content-Length: 4' + CRLF +
       CRLF +
       'pong');
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(method, undefined);
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 1);
-    assert.equal(statusCode, 200);
-    assert.equal(statusMessage, 'OK');
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, undefined);
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 1);
+    assert.strictEqual(statusCode, 200);
+    assert.strictEqual(statusMessage, 'OK');
   };
 
-  var onBody = function(buf, start, len) {
-    var body = '' + buf.slice(start, start + len);
-    assert.equal(body, 'pong');
+  const onBody = function(buf, start, len) {
+    const body = '' + buf.slice(start, start + len);
+    assert.strictEqual(body, 'pong');
   };
 
-  var parser = newParser(RESPONSE);
+  const parser = newParser(RESPONSE);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser[kOnBody] = mustCall(onBody);
   parser.execute(request, 0, request.length);
-})();
+}
 
 
 //
 // Response with no headers.
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'HTTP/1.0 200 Connection established' + CRLF +
       CRLF);
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 0);
-    assert.equal(method, undefined);
-    assert.equal(statusCode, 200);
-    assert.equal(statusMessage, 'Connection established');
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 0);
+    assert.strictEqual(method, undefined);
+    assert.strictEqual(statusCode, 200);
+    assert.strictEqual(statusMessage, 'Connection established');
     assert.deepStrictEqual(headers || parser.headers, []);
   };
 
-  var parser = newParser(RESPONSE);
+  const parser = newParser(RESPONSE);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser.execute(request, 0, request.length);
-})();
+}
 
 
 //
 // Trailing headers.
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'POST /it HTTP/1.1' + CRLF +
       'Transfer-Encoding: chunked' + CRLF +
       CRLF +
@@ -180,139 +180,139 @@ function expectBody(expected) {
       'Content-Type: text/plain' + CRLF +
       CRLF);
 
-  var seen_body = false;
+  let seen_body = false;
 
-  var onHeaders = function(headers, url) {
+  const onHeaders = function(headers, url) {
     assert.ok(seen_body); // trailers should come after the body
     assert.deepStrictEqual(headers,
                            ['Vary', '*', 'Content-Type', 'text/plain']);
   };
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(method, methods.indexOf('POST'));
-    assert.equal(url || parser.url, '/it');
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 1);
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, methods.indexOf('POST'));
+    assert.strictEqual(url || parser.url, '/it');
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 1);
     // expect to see trailing headers now
     parser[kOnHeaders] = mustCall(onHeaders);
   };
 
-  var onBody = function(buf, start, len) {
-    var body = '' + buf.slice(start, start + len);
-    assert.equal(body, 'ping');
+  const onBody = function(buf, start, len) {
+    const body = '' + buf.slice(start, start + len);
+    assert.strictEqual(body, 'ping');
     seen_body = true;
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser[kOnBody] = mustCall(onBody);
   parser.execute(request, 0, request.length);
-})();
+}
 
 
 //
 // Test header ordering.
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'GET / HTTP/1.0' + CRLF +
       'X-Filler: 1337' + CRLF +
       'X-Filler:   42' + CRLF +
       'X-Filler2:  42' + CRLF +
       CRLF);
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(method, methods.indexOf('GET'));
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 0);
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, methods.indexOf('GET'));
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 0);
     assert.deepStrictEqual(
         headers || parser.headers,
         ['X-Filler', '1337', 'X-Filler', '42', 'X-Filler2', '42']);
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser.execute(request, 0, request.length);
-})();
+}
 
 
 //
 // Test large number of headers
 //
-(function() {
+{
   // 256 X-Filler headers
-  var lots_of_headers = 'X-Filler: 42' + CRLF;
+  let lots_of_headers = 'X-Filler: 42' + CRLF;
   lots_of_headers = lots_of_headers.repeat(256);
 
-  var request = Buffer.from(
+  const request = Buffer.from(
       'GET /foo/bar/baz?quux=42#1337 HTTP/1.0' + CRLF +
       lots_of_headers +
       CRLF);
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(method, methods.indexOf('GET'));
-    assert.equal(url || parser.url, '/foo/bar/baz?quux=42#1337');
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 0);
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, methods.indexOf('GET'));
+    assert.strictEqual(url || parser.url, '/foo/bar/baz?quux=42#1337');
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 0);
 
     headers = headers || parser.headers;
 
-    assert.equal(headers.length, 2 * 256); // 256 key/value pairs
-    for (var i = 0; i < headers.length; i += 2) {
-      assert.equal(headers[i], 'X-Filler');
-      assert.equal(headers[i + 1], '42');
+    assert.strictEqual(headers.length, 2 * 256); // 256 key/value pairs
+    for (let i = 0; i < headers.length; i += 2) {
+      assert.strictEqual(headers[i], 'X-Filler');
+      assert.strictEqual(headers[i + 1], '42');
     }
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser.execute(request, 0, request.length);
-})();
+}
 
 
 //
 // Test request body
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'POST /it HTTP/1.1' + CRLF +
       'Content-Type: application/x-www-form-urlencoded' + CRLF +
       'Content-Length: 15' + CRLF +
       CRLF +
       'foo=42&bar=1337');
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(method, methods.indexOf('POST'));
-    assert.equal(url || parser.url, '/it');
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 1);
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, methods.indexOf('POST'));
+    assert.strictEqual(url || parser.url, '/it');
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 1);
   };
 
-  var onBody = function(buf, start, len) {
-    var body = '' + buf.slice(start, start + len);
-    assert.equal(body, 'foo=42&bar=1337');
+  const onBody = function(buf, start, len) {
+    const body = '' + buf.slice(start, start + len);
+    assert.strictEqual(body, 'foo=42&bar=1337');
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser[kOnBody] = mustCall(onBody);
   parser.execute(request, 0, request.length);
-})();
+}
 
 
 //
 // Test chunked request body
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'POST /it HTTP/1.1' + CRLF +
       'Content-Type: text/plain' + CRLF +
       'Transfer-Encoding: chunked' + CRLF +
@@ -325,35 +325,35 @@ function expectBody(expected) {
       '1234567890' + CRLF +
       '0' + CRLF);
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(method, methods.indexOf('POST'));
-    assert.equal(url || parser.url, '/it');
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 1);
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, methods.indexOf('POST'));
+    assert.strictEqual(url || parser.url, '/it');
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 1);
   };
 
   let body_part = 0;
   const body_parts = ['123', '123456', '1234567890'];
 
-  var onBody = function(buf, start, len) {
-    var body = '' + buf.slice(start, start + len);
-    assert.equal(body, body_parts[body_part++]);
+  const onBody = function(buf, start, len) {
+    const body = '' + buf.slice(start, start + len);
+    assert.strictEqual(body, body_parts[body_part++]);
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser[kOnBody] = mustCall(onBody, body_parts.length);
   parser.execute(request, 0, request.length);
-})();
+}
 
 
 //
 // Test chunked request body spread over multiple buffers (packets)
 //
-(function() {
-  var request = Buffer.from(
+{
+  let request = Buffer.from(
       'POST /it HTTP/1.1' + CRLF +
       'Content-Type: text/plain' + CRLF +
       'Transfer-Encoding: chunked' + CRLF +
@@ -363,25 +363,25 @@ function expectBody(expected) {
       '6' + CRLF +
       '123456' + CRLF);
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(method, methods.indexOf('POST'));
-    assert.equal(url || parser.url, '/it');
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 1);
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, methods.indexOf('POST'));
+    assert.strictEqual(url || parser.url, '/it');
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 1);
   };
 
   let body_part = 0;
   const body_parts =
           ['123', '123456', '123456789', '123456789ABC', '123456789ABCDEF'];
 
-  var onBody = function(buf, start, len) {
-    var body = '' + buf.slice(start, start + len);
-    assert.equal(body, body_parts[body_part++]);
+  const onBody = function(buf, start, len) {
+    const body = '' + buf.slice(start, start + len);
+    assert.strictEqual(body, body_parts[body_part++]);
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser[kOnBody] = mustCall(onBody, body_parts.length);
   parser.execute(request, 0, request.length);
@@ -396,14 +396,14 @@ function expectBody(expected) {
       '0' + CRLF);
 
   parser.execute(request, 0, request.length);
-})();
+}
 
 
 //
 // Stress test.
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'POST /helpme HTTP/1.1' + CRLF +
       'Content-Type: text/plain' + CRLF +
       'Transfer-Encoding: chunked' + CRLF +
@@ -421,30 +421,30 @@ function expectBody(expected) {
       '0' + CRLF);
 
   function test(a, b) {
-    var onHeadersComplete = function(versionMajor, versionMinor, headers,
-                                     method, url, statusCode, statusMessage,
-                                     upgrade, shouldKeepAlive) {
-      assert.equal(method, methods.indexOf('POST'));
-      assert.equal(url || parser.url, '/helpme');
-      assert.equal(versionMajor, 1);
-      assert.equal(versionMinor, 1);
+    const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                       method, url, statusCode, statusMessage,
+                                       upgrade, shouldKeepAlive) {
+      assert.strictEqual(method, methods.indexOf('POST'));
+      assert.strictEqual(url || parser.url, '/helpme');
+      assert.strictEqual(versionMajor, 1);
+      assert.strictEqual(versionMinor, 1);
     };
 
-    var expected_body = '123123456123456789123456789ABC123456789ABCDEF';
+    let expected_body = '123123456123456789123456789ABC123456789ABCDEF';
 
-    var onBody = function(buf, start, len) {
-      var chunk = '' + buf.slice(start, start + len);
-      assert.equal(expected_body.indexOf(chunk), 0);
+    const onBody = function(buf, start, len) {
+      const chunk = '' + buf.slice(start, start + len);
+      assert.strictEqual(expected_body.indexOf(chunk), 0);
       expected_body = expected_body.slice(chunk.length);
     };
 
-    var parser = newParser(REQUEST);
+    const parser = newParser(REQUEST);
     parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
     parser[kOnBody] = onBody;
     parser.execute(a, 0, a.length);
     parser.execute(b, 0, b.length);
 
-    assert.equal(expected_body, '');
+    assert.strictEqual(expected_body, '');
   }
 
   for (var i = 1; i < request.length - 1; ++i) {
@@ -456,14 +456,14 @@ function expectBody(expected) {
                   JSON.stringify(b.toString()));
     test(a, b);
   }
-})();
+}
 
 
 //
 // Byte by byte test.
 //
-(function() {
-  var request = Buffer.from(
+{
+  const request = Buffer.from(
       'POST /it HTTP/1.1' + CRLF +
       'Content-Type: text/plain' + CRLF +
       'Transfer-Encoding: chunked' + CRLF +
@@ -480,43 +480,43 @@ function expectBody(expected) {
       '123456789ABCDEF' + CRLF +
       '0' + CRLF);
 
-  var onHeadersComplete = function(versionMajor, versionMinor, headers, method,
-                                   url, statusCode, statusMessage, upgrade,
-                                   shouldKeepAlive) {
-    assert.equal(method, methods.indexOf('POST'));
-    assert.equal(url || parser.url, '/it');
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 1);
+  const onHeadersComplete = function(versionMajor, versionMinor, headers,
+                                     method, url, statusCode, statusMessage,
+                                     upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, methods.indexOf('POST'));
+    assert.strictEqual(url || parser.url, '/it');
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 1);
     assert.deepStrictEqual(
         headers || parser.headers,
         ['Content-Type', 'text/plain', 'Transfer-Encoding', 'chunked']);
   };
 
-  var expected_body = '123123456123456789123456789ABC123456789ABCDEF';
+  let expected_body = '123123456123456789123456789ABC123456789ABCDEF';
 
-  var onBody = function(buf, start, len) {
-    var chunk = '' + buf.slice(start, start + len);
-    assert.equal(expected_body.indexOf(chunk), 0);
+  const onBody = function(buf, start, len) {
+    const chunk = '' + buf.slice(start, start + len);
+    assert.strictEqual(expected_body.indexOf(chunk), 0);
     expected_body = expected_body.slice(chunk.length);
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = mustCall(onHeadersComplete);
   parser[kOnBody] = onBody;
 
-  for (var i = 0; i < request.length; ++i) {
+  for (let i = 0; i < request.length; ++i) {
     parser.execute(request, i, 1);
   }
 
-  assert.equal(expected_body, '');
-})();
+  assert.strictEqual(expected_body, '');
+}
 
 
 //
 // Test parser reinit sequence.
 //
-(function() {
-  var req1 = Buffer.from(
+{
+  const req1 = Buffer.from(
       'PUT /this HTTP/1.1' + CRLF +
       'Content-Type: text/plain' + CRLF +
       'Transfer-Encoding: chunked' + CRLF +
@@ -525,16 +525,16 @@ function expectBody(expected) {
       'ping' + CRLF +
       '0' + CRLF);
 
-  var req2 = Buffer.from(
+  const req2 = Buffer.from(
       'POST /that HTTP/1.0' + CRLF +
       'Content-Type: text/plain' + CRLF +
       'Content-Length: 4' + CRLF +
       CRLF +
       'pong');
 
-  var onHeadersComplete1 = function(versionMajor, versionMinor, headers, method,
-                                    url, statusCode, statusMessage, upgrade,
-                                    shouldKeepAlive) {
+  const onHeadersComplete1 = function(versionMajor, versionMinor, headers,
+                                      method, url, statusCode, statusMessage,
+                                      upgrade, shouldKeepAlive) {
     assert.equal(method, methods.indexOf('PUT'));
     assert.equal(url, '/this');
     assert.equal(versionMajor, 1);
@@ -544,20 +544,20 @@ function expectBody(expected) {
         ['Content-Type', 'text/plain', 'Transfer-Encoding', 'chunked']);
   };
 
-  var onHeadersComplete2 = function(versionMajor, versionMinor, headers, method,
-                                    url, statusCode, statusMessage, upgrade,
-                                    shouldKeepAlive) {
-    assert.equal(method, methods.indexOf('POST'));
-    assert.equal(url, '/that');
-    assert.equal(versionMajor, 1);
-    assert.equal(versionMinor, 0);
+  const onHeadersComplete2 = function(versionMajor, versionMinor, headers,
+                                      method, url, statusCode, statusMessage,
+                                      upgrade, shouldKeepAlive) {
+    assert.strictEqual(method, methods.indexOf('POST'));
+    assert.strictEqual(url, '/that');
+    assert.strictEqual(versionMajor, 1);
+    assert.strictEqual(versionMinor, 0);
     assert.deepStrictEqual(
       headers,
       ['Content-Type', 'text/plain', 'Content-Length', '4']
     );
   };
 
-  var parser = newParser(REQUEST);
+  const parser = newParser(REQUEST);
   parser[kOnHeadersComplete] = onHeadersComplete1;
   parser[kOnBody] = expectBody('ping');
   parser.execute(req1, 0, req1.length);
@@ -566,7 +566,7 @@ function expectBody(expected) {
   parser[kOnBody] = expectBody('pong');
   parser[kOnHeadersComplete] = onHeadersComplete2;
   parser.execute(req2, 0, req2.length);
-})();
+}
 
 // Test parser 'this' safety
 // https://github.com/joyent/node/issues/6690
diff --git a/test/parallel/test-querystring.js b/test/parallel/test-querystring.js
index 5d52fe6544..37cf66705d 100644
--- a/test/parallel/test-querystring.js
+++ b/test/parallel/test-querystring.js
@@ -134,7 +134,7 @@ qsNoMungeTestCases.forEach(function(testCase) {
 });
 
 // test the nested qs-in-qs case
-(function() {
+{
   const f = qs.parse('a=b&q=x%3Dy%26y%3Dz');
   check(f, createWithNoPrototype([
     { key: 'a', value: 'b'},
@@ -147,10 +147,10 @@ qsNoMungeTestCases.forEach(function(testCase) {
     {key: 'y', value: 'z' }
   ]);
   check(f.q, expectedInternal);
-})();
+}
 
 // nested in colon
-(function() {
+{
   const f = qs.parse('a:b;q:x%3Ay%3By%3Az', ';', ':');
   check(f, createWithNoPrototype([
     {key: 'a', value: 'b'},
@@ -162,7 +162,7 @@ qsNoMungeTestCases.forEach(function(testCase) {
     {key: 'y', value: 'z' }
   ]);
   check(f.q, expectedInternal);
-})();
+}
 
 // now test stringifying
 
diff --git a/test/parallel/test-require-cache.js b/test/parallel/test-require-cache.js
index 7ea68dd051..247590197d 100644
--- a/test/parallel/test-require-cache.js
+++ b/test/parallel/test-require-cache.js
@@ -2,22 +2,22 @@
 require('../common');
 var assert = require('assert');
 
-(function testInjectFakeModule() {
-  var relativePath = '../fixtures/semicolon';
-  var absolutePath = require.resolve(relativePath);
-  var fakeModule = {};
+{
+  const relativePath = '../fixtures/semicolon';
+  const absolutePath = require.resolve(relativePath);
+  const fakeModule = {};
 
   require.cache[absolutePath] = {exports: fakeModule};
 
   assert.strictEqual(require(relativePath), fakeModule);
-})();
+}
 
 
-(function testInjectFakeNativeModule() {
-  var relativePath = 'fs';
-  var fakeModule = {};
+{
+  const relativePath = 'fs';
+  const fakeModule = {};
 
   require.cache[relativePath] = {exports: fakeModule};
 
   assert.strictEqual(require(relativePath), fakeModule);
-})();
+}
diff --git a/test/parallel/test-stream-pipe-error-handling.js b/test/parallel/test-stream-pipe-error-handling.js
index 88a70fb58e..b2c25cfe8c 100644
--- a/test/parallel/test-stream-pipe-error-handling.js
+++ b/test/parallel/test-stream-pipe-error-handling.js
@@ -1,33 +1,33 @@
 'use strict';
-require('../common');
-var assert = require('assert');
-var Stream = require('stream').Stream;
+const common = require('../common');
+const assert = require('assert');
+const Stream = require('stream').Stream;
 
-(function testErrorListenerCatches() {
-  var source = new Stream();
-  var dest = new Stream();
+{
+  const source = new Stream();
+  const dest = new Stream();
 
   source.pipe(dest);
 
-  var gotErr = null;
+  let gotErr = null;
   source.on('error', function(err) {
     gotErr = err;
   });
 
-  var err = new Error('This stream turned into bacon.');
+  const err = new Error('This stream turned into bacon.');
   source.emit('error', err);
   assert.strictEqual(gotErr, err);
-})();
+}
 
-(function testErrorWithoutListenerThrows() {
-  var source = new Stream();
-  var dest = new Stream();
+{
+  const source = new Stream();
+  const dest = new Stream();
 
   source.pipe(dest);
 
-  var err = new Error('This stream turned into bacon.');
+  const err = new Error('This stream turned into bacon.');
 
-  var gotErr = null;
+  let gotErr = null;
   try {
     source.emit('error', err);
   } catch (e) {
@@ -35,30 +35,23 @@ var Stream = require('stream').Stream;
   }
 
   assert.strictEqual(gotErr, err);
-})();
+}
 
-(function testErrorWithRemovedListenerThrows() {
-  var R = Stream.Readable;
-  var W = Stream.Writable;
+{
+  const R = Stream.Readable;
+  const W = Stream.Writable;
 
-  var r = new R();
-  var w = new W();
-  var removed = false;
-  var didTest = false;
-
-  process.on('exit', function() {
-    assert(didTest);
-    console.log('ok');
-  });
+  const r = new R();
+  const w = new W();
+  let removed = false;
 
   r._read = function() {
-    setTimeout(function() {
+    setTimeout(common.mustCall(function() {
       assert(removed);
       assert.throws(function() {
         w.emit('error', new Error('fail'));
       });
-      didTest = true;
-    });
+    }));
   };
 
   w.on('error', myOnError);
@@ -69,41 +62,28 @@ var Stream = require('stream').Stream;
   function myOnError(er) {
     throw new Error('this should not happen');
   }
-})();
+}
 
-(function testErrorWithRemovedListenerThrows() {
-  var R = Stream.Readable;
-  var W = Stream.Writable;
+{
+  const R = Stream.Readable;
+  const W = Stream.Writable;
 
-  var r = new R();
-  var w = new W();
-  var removed = false;
-  var didTest = false;
-  var caught = false;
-
-  process.on('exit', function() {
-    assert(didTest);
-    console.log('ok');
-  });
+  const r = new R();
+  const w = new W();
+  let removed = false;
 
   r._read = function() {
-    setTimeout(function() {
+    setTimeout(common.mustCall(function() {
       assert(removed);
       w.emit('error', new Error('fail'));
-      didTest = true;
-    });
+    }));
   };
 
-  w.on('error', myOnError);
+  w.on('error', common.mustCall(function(er) {}));
   w._write = function() {};
 
   r.pipe(w);
   // Removing some OTHER random listener should not do anything
   w.removeListener('error', function() {});
   removed = true;
-
-  function myOnError(er) {
-    assert(!caught);
-    caught = true;
-  }
-})();
+}
diff --git a/test/parallel/test-stream-readable-event.js b/test/parallel/test-stream-readable-event.js
index 957f409781..a20fc2ee73 100644
--- a/test/parallel/test-stream-readable-event.js
+++ b/test/parallel/test-stream-readable-event.js
@@ -1,106 +1,64 @@
 'use strict';
-require('../common');
-var assert = require('assert');
+const common = require('../common');
+const assert = require('assert');
 
-var Readable = require('stream').Readable;
+const Readable = require('stream').Readable;
 
-(function first() {
+{
   // First test, not reading when the readable is added.
   // make sure that on('readable', ...) triggers a readable event.
-  var r = new Readable({
+  const r = new Readable({
     highWaterMark: 3
   });
 
-  var _readCalled = false;
-  r._read = function(n) {
-    _readCalled = true;
-  };
+  r._read = common.fail;
 
   // This triggers a 'readable' event, which is lost.
   r.push(Buffer.from('blerg'));
 
-  var caughtReadable = false;
   setTimeout(function() {
     // we're testing what we think we are
     assert(!r._readableState.reading);
-    r.on('readable', function() {
-      caughtReadable = true;
-    });
+    r.on('readable', common.mustCall(function() {}));
   });
+}
 
-  process.on('exit', function() {
-    // we're testing what we think we are
-    assert(!_readCalled);
-
-    assert(caughtReadable);
-    console.log('ok 1');
-  });
-})();
-
-(function second() {
+{
   // second test, make sure that readable is re-emitted if there's
   // already a length, while it IS reading.
 
-  var r = new Readable({
+  const r = new Readable({
     highWaterMark: 3
   });
 
-  var _readCalled = false;
-  r._read = function(n) {
-    _readCalled = true;
-  };
+  r._read = common.mustCall(function(n) {});
 
   // This triggers a 'readable' event, which is lost.
   r.push(Buffer.from('bl'));
 
-  var caughtReadable = false;
   setTimeout(function() {
     // assert we're testing what we think we are
     assert(r._readableState.reading);
-    r.on('readable', function() {
-      caughtReadable = true;
-    });
-  });
-
-  process.on('exit', function() {
-    // we're testing what we think we are
-    assert(_readCalled);
-
-    assert(caughtReadable);
-    console.log('ok 2');
+    r.on('readable', common.mustCall(function() {}));
   });
-})();
+}
 
-(function third() {
+{
   // Third test, not reading when the stream has not passed
   // the highWaterMark but *has* reached EOF.
-  var r = new Readable({
+  const r = new Readable({
     highWaterMark: 30
   });
 
-  var _readCalled = false;
-  r._read = function(n) {
-    _readCalled = true;
-  };
+  r._read = common.fail;
 
   // This triggers a 'readable' event, which is lost.
   r.push(Buffer.from('blerg'));
   r.push(null);
 
-  var caughtReadable = false;
   setTimeout(function() {
     // assert we're testing what we think we are
     assert(!r._readableState.reading);
-    r.on('readable', function() {
-      caughtReadable = true;
-    });
-  });
-
-  process.on('exit', function() {
-    // we're testing what we think we are
-    assert(!_readCalled);
-
-    assert(caughtReadable);
-    console.log('ok 3');
+    r.on('readable', common.mustCall(function() {}));
   });
-})();
+}
diff --git a/test/parallel/test-stream-writable-decoded-encoding.js b/test/parallel/test-stream-writable-decoded-encoding.js
index 75d5d42476..621e342a3c 100644
--- a/test/parallel/test-stream-writable-decoded-encoding.js
+++ b/test/parallel/test-stream-writable-decoded-encoding.js
@@ -17,24 +17,22 @@ MyWritable.prototype._write = function(chunk, encoding, callback) {
   callback();
 };
 
-(function decodeStringsTrue() {
-  var m = new MyWritable(function(isBuffer, type, enc) {
+{
+  const m = new MyWritable(function(isBuffer, type, enc) {
     assert(isBuffer);
-    assert.equal(type, 'object');
-    assert.equal(enc, 'buffer');
-    console.log('ok - decoded string is decoded');
+    assert.strictEqual(type, 'object');
+    assert.strictEqual(enc, 'buffer');
   }, { decodeStrings: true });
   m.write('some-text', 'utf8');
   m.end();
-})();
+}
 
-(function decodeStringsFalse() {
-  var m = new MyWritable(function(isBuffer, type, enc) {
+{
+  const m = new MyWritable(function(isBuffer, type, enc) {
     assert(!isBuffer);
-    assert.equal(type, 'string');
-    assert.equal(enc, 'utf8');
-    console.log('ok - un-decoded string is not decoded');
+    assert.strictEqual(type, 'string');
+    assert.strictEqual(enc, 'utf8');
   }, { decodeStrings: false });
   m.write('some-text', 'utf8');
   m.end();
-})();
+}
diff --git a/test/parallel/test-stream2-pipe-error-handling.js b/test/parallel/test-stream2-pipe-error-handling.js
index 65397566c2..bdf7a4a9a3 100644
--- a/test/parallel/test-stream2-pipe-error-handling.js
+++ b/test/parallel/test-stream2-pipe-error-handling.js
@@ -3,77 +3,77 @@ require('../common');
 var assert = require('assert');
 var stream = require('stream');
 
-(function testErrorListenerCatches() {
-  var count = 1000;
+{
+  let count = 1000;
 
-  var source = new stream.Readable();
+  const source = new stream.Readable();
   source._read = function(n) {
     n = Math.min(count, n);
     count -= n;
     source.push(Buffer.allocUnsafe(n));
   };
 
-  var unpipedDest;
+  let unpipedDest;
   source.unpipe = function(dest) {
     unpipedDest = dest;
     stream.Readable.prototype.unpipe.call(this, dest);
   };
 
-  var dest = new stream.Writable();
+  const dest = new stream.Writable();
   dest._write = function(chunk, encoding, cb) {
     cb();
   };
 
   source.pipe(dest);
 
-  var gotErr = null;
+  let gotErr = null;
   dest.on('error', function(err) {
     gotErr = err;
   });
 
-  var unpipedSource;
+  let unpipedSource;
   dest.on('unpipe', function(src) {
     unpipedSource = src;
   });
 
-  var err = new Error('This stream turned into bacon.');
+  const err = new Error('This stream turned into bacon.');
   dest.emit('error', err);
   assert.strictEqual(gotErr, err);
   assert.strictEqual(unpipedSource, source);
   assert.strictEqual(unpipedDest, dest);
-})();
+}
 
-(function testErrorWithoutListenerThrows() {
-  var count = 1000;
+{
+  let count = 1000;
 
-  var source = new stream.Readable();
+  const source = new stream.Readable();
   source._read = function(n) {
     n = Math.min(count, n);
     count -= n;
     source.push(Buffer.allocUnsafe(n));
   };
 
-  var unpipedDest;
+  let unpipedDest;
   source.unpipe = function(dest) {
     unpipedDest = dest;
     stream.Readable.prototype.unpipe.call(this, dest);
   };
 
-  var dest = new stream.Writable();
+  const dest = new stream.Writable();
   dest._write = function(chunk, encoding, cb) {
     cb();
   };
 
   source.pipe(dest);
 
-  var unpipedSource;
+  let unpipedSource;
   dest.on('unpipe', function(src) {
     unpipedSource = src;
   });
 
-  var err = new Error('This stream turned into bacon.');
+  const err = new Error('This stream turned into bacon.');
 
-  var gotErr = null;
+  let gotErr = null;
   try {
     dest.emit('error', err);
   } catch (e) {
@@ -82,4 +82,4 @@ var stream = require('stream');
   assert.strictEqual(gotErr, err);
   assert.strictEqual(unpipedSource, source);
   assert.strictEqual(unpipedDest, dest);
-})();
+}
diff --git a/test/parallel/test-stringbytes-external.js b/test/parallel/test-stringbytes-external.js
index ec7ae5aa75..a34612f75d 100644
--- a/test/parallel/test-stringbytes-external.js
+++ b/test/parallel/test-stringbytes-external.js
@@ -66,57 +66,57 @@ var RADIOS = 2;
 var PRE_HALF_APEX = Math.ceil(EXTERN_APEX / 2) - RADIOS;
 var PRE_3OF4_APEX = Math.ceil((EXTERN_APEX / 4) * 3) - RADIOS;
 
-(function() {
-  for (var j = 0; j < RADIOS * 2; j += 1) {
-    var datum = b;
-    var slice = datum.slice(0, PRE_HALF_APEX + j);
-    var slice2 = datum.slice(0, PRE_HALF_APEX + j + 2);
-    var pumped_string = slice.toString('hex');
-    var pumped_string2 = slice2.toString('hex');
-    var decoded = Buffer.from(pumped_string, 'hex');
+{
+  for (let j = 0; j < RADIOS * 2; j += 1) {
+    const datum = b;
+    const slice = datum.slice(0, PRE_HALF_APEX + j);
+    const slice2 = datum.slice(0, PRE_HALF_APEX + j + 2);
+    const pumped_string = slice.toString('hex');
+    const pumped_string2 = slice2.toString('hex');
+    const decoded = Buffer.from(pumped_string, 'hex');
 
     // the string are the same?
-    for (var k = 0; k < pumped_string.length; ++k) {
-      assert.equal(pumped_string[k], pumped_string2[k]);
+    for (let k = 0; k < pumped_string.length; ++k) {
+      assert.strictEqual(pumped_string[k], pumped_string2[k]);
     }
 
     // the recoded buffer is the same?
-    for (var i = 0; i < decoded.length; ++i) {
-      assert.equal(datum[i], decoded[i]);
+    for (let i = 0; i < decoded.length; ++i) {
+      assert.strictEqual(datum[i], decoded[i]);
     }
   }
-})();
+}
 
-(function() {
-  for (var j = 0; j < RADIOS * 2; j += 1) {
-    var datum = b;
-    var slice = datum.slice(0, PRE_3OF4_APEX + j);
-    var slice2 = datum.slice(0, PRE_3OF4_APEX + j + 2);
-    var pumped_string = slice.toString('base64');
-    var pumped_string2 = slice2.toString('base64');
-    var decoded = Buffer.from(pumped_string, 'base64');
+{
+  for (let j = 0; j < RADIOS * 2; j += 1) {
+    const datum = b;
+    const slice = datum.slice(0, PRE_3OF4_APEX + j);
+    const slice2 = datum.slice(0, PRE_3OF4_APEX + j + 2);
+    const pumped_string = slice.toString('base64');
+    const pumped_string2 = slice2.toString('base64');
+    const decoded = Buffer.from(pumped_string, 'base64');
 
     // the string are the same?
-    for (var k = 0; k < pumped_string.length - 3; ++k) {
-      assert.equal(pumped_string[k], pumped_string2[k]);
+    for (let k = 0; k < pumped_string.length - 3; ++k) {
+      assert.strictEqual(pumped_string[k], pumped_string2[k]);
     }
 
     // the recoded buffer is the same?
-    for (var i = 0; i < decoded.length; ++i) {
-      assert.equal(datum[i], decoded[i]);
+    for (let i = 0; i < decoded.length; ++i) {
+      assert.strictEqual(datum[i], decoded[i]);
     }
   }
-})();
+}
 
 // https://github.com/nodejs/node/issues/1024
-(function() {
-  var a = Array(1 << 20).join('x');
-  var b = Buffer.from(a, 'ucs2').toString('ucs2');
-  var c = Buffer.from(b, 'utf8').toString('utf8');
+{
+  const a = Array(1 << 20).join('x');
+  const b = Buffer.from(a, 'ucs2').toString('ucs2');
+  const c = Buffer.from(b, 'utf8').toString('utf8');
 
-  assert.equal(a.length, b.length);
-  assert.equal(b.length, c.length);
+  assert.strictEqual(a.length, b.length);
+  assert.strictEqual(b.length, c.length);
 
-  assert.equal(a, b);
-  assert.equal(b, c);
-})();
+  assert.strictEqual(a, b);
+  assert.strictEqual(b, c);
+}
diff --git a/test/parallel/test-timers-unref.js b/test/parallel/test-timers-unref.js
index 570c51b9ac..801b34792a 100644
--- a/test/parallel/test-timers-unref.js
+++ b/test/parallel/test-timers-unref.js
@@ -55,11 +55,11 @@ setInterval(function() {
 }, SHORT_TIME);
 
 // Should not assert on args.Holder()->InternalFieldCount() > 0. See #4261.
-(function() {
-  var t = setInterval(function() {}, 1);
+{
+  const t = setInterval(function() {}, 1);
   process.nextTick(t.unref.bind({}));
   process.nextTick(t.unref.bind(t));
-})();
+}
 
 process.on('exit', function() {
   assert.strictEqual(interval_fired, false,
diff --git a/test/parallel/test-timers-zero-timeout.js b/test/parallel/test-timers-zero-timeout.js
index ab0c38f608..00e75b7ea8 100644
--- a/test/parallel/test-timers-zero-timeout.js
+++ b/test/parallel/test-timers-zero-timeout.js
@@ -1,39 +1,32 @@
 'use strict';
-require('../common');
-var assert = require('assert');
+const common = require('../common');
+const assert = require('assert');
 
 // https://github.com/joyent/node/issues/2079 - zero timeout drops extra args
-(function() {
-  var ncalled = 0;
-
-  setTimeout(f, 0, 'foo', 'bar', 'baz');
+{
+  setTimeout(common.mustCall(f), 0, 'foo', 'bar', 'baz');
   setTimeout(function() {}, 0);
 
   function f(a, b, c) {
-    assert.equal(a, 'foo');
-    assert.equal(b, 'bar');
-    assert.equal(c, 'baz');
-    ncalled++;
+    assert.strictEqual(a, 'foo');
+    assert.strictEqual(b, 'bar');
+    assert.strictEqual(c, 'baz');
   }
+}
 
-  process.on('exit', function() {
-    assert.equal(ncalled, 1);
-  });
-})();
-
-(function() {
-  var ncalled = 0;
+{
+  let ncalled = 0;
 
-  var iv = setInterval(f, 0, 'foo', 'bar', 'baz');
+  const iv = setInterval(f, 0, 'foo', 'bar', 'baz');
 
   function f(a, b, c) {
-    assert.equal(a, 'foo');
-    assert.equal(b, 'bar');
-    assert.equal(c, 'baz');
+    assert.strictEqual(a, 'foo');
+    assert.strictEqual(b, 'bar');
+    assert.strictEqual(c, 'baz');
     if (++ncalled == 3) clearTimeout(iv);
   }
 
   process.on('exit', function() {
-    assert.equal(ncalled, 3);
+    assert.strictEqual(ncalled, 3);
   });
-})();
+}
diff --git a/test/parallel/test-tls-connect.js b/test/parallel/test-tls-connect.js
index 3853ea66bc..96de1b0ad6 100644
--- a/test/parallel/test-tls-connect.js
+++ b/test/parallel/test-tls-connect.js
@@ -13,37 +13,38 @@ var path = require('path');
 
 // https://github.com/joyent/node/issues/1218
 // uncatchable exception on TLS connection error
-(function() {
-  var cert = fs.readFileSync(path.join(common.fixturesDir, 'test_cert.pem'));
-  var key = fs.readFileSync(path.join(common.fixturesDir, 'test_key.pem'));
+{
+  const cert = fs.readFileSync(path.join(common.fixturesDir, 'test_cert.pem'));
+  const key = fs.readFileSync(path.join(common.fixturesDir, 'test_key.pem'));
 
-  var errorEmitted = false;
+  let errorEmitted = false;
 
   process.on('exit', function() {
     assert.ok(errorEmitted);
   });
 
-  var conn = tls.connect({cert: cert, key: key, port: common.PORT}, function() {
+  const options = {cert: cert, key: key, port: common.PORT};
+  const conn = tls.connect(options, function() {
     assert.ok(false); // callback should never be executed
   });
 
   conn.on('error', function() {
     errorEmitted = true;
   });
-})();
+}
 
 // SSL_accept/SSL_connect error handling
-(function() {
-  var cert = fs.readFileSync(path.join(common.fixturesDir, 'test_cert.pem'));
-  var key = fs.readFileSync(path.join(common.fixturesDir, 'test_key.pem'));
+{
+  const cert = fs.readFileSync(path.join(common.fixturesDir, 'test_cert.pem'));
+  const key = fs.readFileSync(path.join(common.fixturesDir, 'test_key.pem'));
 
-  var errorEmitted = false;
+  let errorEmitted = false;
 
   process.on('exit', function() {
     assert.ok(errorEmitted);
   });
 
-  var conn = tls.connect({
+  const conn = tls.connect({
     cert: cert,
     key: key,
     port: common.PORT,
@@ -55,4 +56,4 @@ var path = require('path');
   conn.on('error', function() {
     errorEmitted = true;
   });
-})();
+}
diff --git a/test/parallel/test-util-format.js b/test/parallel/test-util-format.js
index 92c448578b..f3702ef2f0 100644
--- a/test/parallel/test-util-format.js
+++ b/test/parallel/test-util-format.js
@@ -48,11 +48,11 @@ assert.equal(util.format('%s:%s', 'foo', 'bar', 'baz'), 'foo:bar baz');
 assert.equal(util.format('%%%s%%', 'hi'), '%hi%');
 assert.equal(util.format('%%%s%%%%', 'hi'), '%hi%%');
 
-(function() {
-  var o = {};
+{
+  const o = {};
   o.o = o;
   assert.equal(util.format('%j', o), '[Circular]');
-})();
+}
 
 // Errors
 const err = new Error('foo');
diff --git a/test/parallel/test-vm-debug-context.js b/test/parallel/test-vm-debug-context.js
index 07335fad56..9b8da58756 100644
--- a/test/parallel/test-vm-debug-context.js
+++ b/test/parallel/test-vm-debug-context.js
@@ -31,9 +31,9 @@ assert.strictEqual(vm.runInDebugContext(undefined), undefined);
 
 // See https://github.com/nodejs/node/issues/1190, accessing named interceptors
 // and accessors inside a debug event listener should not crash.
-(function() {
-  var Debug = vm.runInDebugContext('Debug');
-  var breaks = 0;
+{
+  const Debug = vm.runInDebugContext('Debug');
+  let breaks = 0;
 
   function ondebugevent(evt, exc) {
     if (evt !== Debug.DebugEvent.Break) return;
@@ -51,10 +51,10 @@ assert.strictEqual(vm.runInDebugContext(undefined), undefined);
   assert.equal(breaks, 0);
   breakpoint();
   assert.equal(breaks, 1);
-})();
+}
 
 // Can set listeners and breakpoints on a single line file
-(function() {
+{
   const Debug = vm.runInDebugContext('Debug');
   const fn = require(common.fixturesDir + '/exports-function-with-param');
   let called = false;
@@ -69,7 +69,7 @@ assert.strictEqual(vm.runInDebugContext(undefined), undefined);
   fn('foo');
   assert.strictEqual(Debug.showBreakPoints(fn), '(arg) { [B0]return arg; }');
   assert.strictEqual(called, true);
-})();
+}
 
 // See https://github.com/nodejs/node/issues/1190, fatal errors should not
 // crash the process.
diff --git a/test/parallel/test-zlib-dictionary-fail.js b/test/parallel/test-zlib-dictionary-fail.js
index 2c8939c68f..21c94b2c41 100644
--- a/test/parallel/test-zlib-dictionary-fail.js
+++ b/test/parallel/test-zlib-dictionary-fail.js
@@ -4,8 +4,8 @@ var assert = require('assert');
 var zlib = require('zlib');
 
 // Should raise an error, not trigger an assertion in src/node_zlib.cc
-(function() {
-  var stream = zlib.createInflate();
+{
+  const stream = zlib.createInflate();
 
   stream.on('error', common.mustCall(function(err) {
     assert(/Missing dictionary/.test(err.message));
@@ -13,11 +13,11 @@ var zlib = require('zlib');
 
   // String "test" encoded with dictionary "dict".
   stream.write(Buffer.from([0x78, 0xBB, 0x04, 0x09, 0x01, 0xA5]));
-})();
+}
 
 // Should raise an error, not trigger an assertion in src/node_zlib.cc
-(function() {
-  var stream = zlib.createInflate({ dictionary: Buffer.from('fail') });
+{
+  const stream = zlib.createInflate({ dictionary: Buffer.from('fail') });
 
   stream.on('error', common.mustCall(function(err) {
     assert(/Bad dictionary/.test(err.message));
@@ -25,4 +25,4 @@ var zlib = require('zlib');
 
   // String "test" encoded with dictionary "dict".
   stream.write(Buffer.from([0x78, 0xBB, 0x04, 0x09, 0x01, 0xA5]));
-})();
+}
diff --git a/test/pummel/test-https-ci-reneg-attack.js b/test/pummel/test-https-ci-reneg-attack.js
index 701963606e..8bda7cc102 100644
--- a/test/pummel/test-https-ci-reneg-attack.js
+++ b/test/pummel/test-https-ci-reneg-attack.js
@@ -20,15 +20,15 @@ if (!common.opensslCli) {
 // renegotiation limits to test
 var LIMITS = [0, 1, 2, 3, 5, 10, 16];
 
-(function() {
-  var n = 0;
+{
+  let n = 0;
   function next() {
     if (n >= LIMITS.length) return;
     tls.CLIENT_RENEG_LIMIT = LIMITS[n++];
     test(next);
   }
   next();
-})();
+}
 
 function test(next) {
   var options = {
diff --git a/test/pummel/test-net-connect-memleak.js b/test/pummel/test-net-connect-memleak.js
index e30ca2e6b0..7c74011755 100644
--- a/test/pummel/test-net-connect-memleak.js
+++ b/test/pummel/test-net-connect-memleak.js
@@ -9,10 +9,11 @@ assert(typeof global.gc === 'function', 'Run this test with --expose-gc');
 net.createServer(function() {}).listen(common.PORT);
 
 var before = 0;
-(function() {
+{
   // 2**26 == 64M entries
   global.gc();
-  for (var i = 0, junk = [0]; i < 26; ++i) junk = junk.concat(junk);
+  let junk = [0];
+  for (let i = 0; i < 26; ++i) junk = junk.concat(junk);
   before = process.memoryUsage().rss;
 
   net.createConnection(common.PORT, '127.0.0.1', function() {
@@ -20,7 +21,7 @@ var before = 0;
     setTimeout(done, 10);
     global.gc();
   });
-})();
+}
 
 function done() {
   global.gc();
diff --git a/test/pummel/test-tls-ci-reneg-attack.js b/test/pummel/test-tls-ci-reneg-attack.js
index b62b894435..5075806c10 100644
--- a/test/pummel/test-tls-ci-reneg-attack.js
+++ b/test/pummel/test-tls-ci-reneg-attack.js
@@ -19,15 +19,15 @@ if (!common.opensslCli) {
 // renegotiation limits to test
 var LIMITS = [0, 1, 2, 3, 5, 10, 16];
 
-(function() {
-  var n = 0;
+{
+  let n = 0;
   function next() {
     if (n >= LIMITS.length) return;
     tls.CLIENT_RENEG_LIMIT = LIMITS[n++];
     test(next);
   }
   next();
-})();
+}
 
 function test(next) {
   var options = {
diff --git a/test/pummel/test-tls-connect-memleak.js b/test/pummel/test-tls-connect-memleak.js
index 2ea61ead6f..227d9c56f4 100644
--- a/test/pummel/test-tls-connect-memleak.js
+++ b/test/pummel/test-tls-connect-memleak.js
@@ -19,17 +19,19 @@ tls.createServer({
   key: fs.readFileSync(common.fixturesDir + '/test_key.pem')
 }).listen(common.PORT);
 
-(function() {
+{
   // 2**26 == 64M entries
-  for (var i = 0, junk = [0]; i < 26; ++i) junk = junk.concat(junk);
+  let junk = [0];
 
-  var options = { rejectUnauthorized: false };
+  for (let i = 0; i < 26; ++i) junk = junk.concat(junk);
+
+  const options = { rejectUnauthorized: false };
   tls.connect(common.PORT, '127.0.0.1', options, function() {
     assert(junk.length != 0);  // keep reference alive
     setTimeout(done, 10);
     global.gc();
   });
-})();
+}
 
 function done() {
   var before = process.memoryUsage().rss;
diff --git a/test/sequential/test-child-process-execsync.js b/test/sequential/test-child-process-execsync.js
index 2fad4ba8c2..fc3c0494dc 100644
--- a/test/sequential/test-child-process-execsync.js
+++ b/test/sequential/test-child-process-execsync.js
@@ -70,8 +70,8 @@ assert.strictEqual(ret, msg + '\n',
 }
 
 // Verify that stderr is not accessed when stdio = 'ignore' - GH #7966
-(function() {
+{
   assert.throws(function() {
     execSync('exit -1', {stdio: 'ignore'});
   }, /Command failed: exit -1/);
-})();
+}