1 files changed, 59 insertions, 0 deletions
diff --git a/date-fns/src/addSeconds/test.ts b/date-fns/src/addSeconds/test.ts
new file mode 100644
index 0000000..86032ed
--- /dev/null
+++ b/date-fns/src/addSeconds/test.ts
@@ -0,0 +1,59 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'assert'
+import addSeconds from '.'
+
+describe('addSeconds', function() {
+  it('adds the given number of seconds', function() {
+    const result = addSeconds(new Date(2014, 6 /* Jul */, 10, 12, 45, 0), 30)
+    assert.deepStrictEqual(result, new Date(2014, 6 /* Jul */, 10, 12, 45, 30))
+  })
+
+  it('accepts a timestamp', function() {
+    const result = addSeconds(
+      new Date(2014, 6 /* Jul */, 10, 12, 45, 0).getTime(),
+      20
+    )
+    assert.deepStrictEqual(result, new Date(2014, 6 /* Jul */, 10, 12, 45, 20))
+  })
+
+  it('converts a fractional number to an integer', function() {
+    const result = addSeconds(
+      new Date(2014, 6 /* Jul */, 10, 12, 45, 0),
+      30.777
+    )
+    assert.deepStrictEqual(result, new Date(2014, 6 /* Jul */, 10, 12, 45, 30))
+  })
+
+  it('implicitly converts number arguments', function() {
+    // @ts-expect-error
+    const result = addSeconds(new Date(2014, 6 /* Jul */, 10, 12, 45, 5), '30')
+    assert.deepStrictEqual(result, new Date(2014, 6 /* Jul */, 10, 12, 45, 35))
+  })
+
+  it('does not mutate the original date', function() {
+    const date = new Date(2014, 6 /* Jul */, 10, 12, 45, 0)
+    addSeconds(date, 15)
+    assert.deepStrictEqual(date, new Date(2014, 6 /* Jul */, 10, 12, 45, 0))
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function() {
+    const result = addSeconds(new Date(NaN), 30)
+    // @ts-expect-error
+    assert(result instanceof Date && isNaN(result))
+  })
+
+  it('returns `Invalid Date` if the given amount is NaN', function() {
+    const result = addSeconds(new Date(2014, 6 /* Jul */, 10, 12, 45, 0), NaN)
+    // @ts-expect-error
+    assert(result instanceof Date && isNaN(result))
+  })
+
+  it('throws TypeError exception if passed less than 2 arguments', function() {
+    // @ts-expect-error
+    assert.throws(addSeconds.bind(null), TypeError)
+    // @ts-expect-error
+    assert.throws(addSeconds.bind(null, 1), TypeError)
+  })
+})