1 files changed, 35 insertions, 0 deletions
diff --git a/date-fns/src/startOfISOWeek/test.ts b/date-fns/src/startOfISOWeek/test.ts
new file mode 100644
index 0000000..6e96187
--- /dev/null
+++ b/date-fns/src/startOfISOWeek/test.ts
@@ -0,0 +1,35 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'power-assert'
+import startOfISOWeek from '.'
+
+describe('startOfISOWeek', function() {
+  it('returns the date with the time set to 00:00:00 and the date set to the first day of an ISO week', function() {
+    const date = new Date(2014, 8 /* Sep */, 2, 11, 55, 0)
+    const result = startOfISOWeek(date)
+    assert.deepEqual(result, new Date(2014, 8 /* Sep */, 1))
+  })
+
+  it('accepts a timestamp', function() {
+    const date = new Date(2014, 1 /* Feb */, 11, 11, 55, 0).getTime()
+    const result = startOfISOWeek(date)
+    assert.deepEqual(result, new Date(2014, 1 /* Feb */, 10))
+  })
+
+  it('does not mutate the original date', function() {
+    const date = new Date(2014, 8 /* Sep */, 2, 11, 55, 0)
+    startOfISOWeek(date)
+    assert.deepEqual(date, new Date(2014, 8 /* Sep */, 2, 11, 55, 0))
+  })
+
+  it('returns `Invalid Date` if the given date is invalid', function() {
+    const result = startOfISOWeek(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(startOfISOWeek.bind(null), TypeError)
+  })
+})