1 files changed, 35 insertions, 0 deletions
diff --git a/date-fns/src/startOfSecond/test.ts b/date-fns/src/startOfSecond/test.ts
new file mode 100644
index 0000000..a7444c1
--- /dev/null
+++ b/date-fns/src/startOfSecond/test.ts
@@ -0,0 +1,35 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'power-assert'
+import startOfSecond from '.'
+
+describe('startOfSecond', function() {
+  it('returns the date with the time set to the first millisecond of a second', function() {
+    const date = new Date(2014, 11 /* Dec */, 1, 22, 15, 45, 400)
+    const result = startOfSecond(date)
+    assert.deepEqual(result, new Date(2014, 11 /* Dec */, 1, 22, 15, 45))
+  })
+
+  it('accepts a timestamp', function() {
+    const date = new Date(2014, 11 /* Dec */, 1, 22, 15, 45, 400).getTime()
+    const result = startOfSecond(date)
+    assert.deepEqual(result, new Date(2014, 11 /* Dec */, 1, 22, 15, 45))
+  })
+
+  it('does not mutate the original date', function() {
+    const date = new Date(2014, 11 /* Dec */, 1, 22, 15, 45, 400)
+    startOfSecond(date)
+    assert.deepEqual(date, new Date(2014, 11 /* Dec */, 1, 22, 15, 45, 400))
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function() {
+    const result = startOfSecond(new Date(NaN))
+    //@ts-expect-error
+    assert(result instanceof Date && isNaN(result))
+  })
+
+  it('throws TypeError exception if passed less than 1 argument', function() {
+    assert.throws(startOfSecond.bind(null), TypeError)
+  })
+})