1 files changed, 34 insertions, 0 deletions
diff --git a/date-fns/src/startOfYesterday/test.ts b/date-fns/src/startOfYesterday/test.ts
new file mode 100644
index 0000000..5847393
--- /dev/null
+++ b/date-fns/src/startOfYesterday/test.ts
@@ -0,0 +1,34 @@
+// @flow
+/* eslint-env mocha */
+
+import assert from 'assert'
+import sinon from 'sinon'
+import startOfYesterday from '.'
+
+describe('startOfYesterday', function() {
+  it('returns the start of yesterday', function() {
+    const clock = sinon.useFakeTimers(
+      new Date(2014, 8 /* Sep */, 25, 14, 30, 45, 500).getTime()
+    )
+
+    const result = startOfYesterday()
+    assert.deepEqual(result, new Date(2014, 8 /* Sep */, 24))
+
+    clock.restore()
+  })
+
+  it('handles dates before 100 AD', function() {
+    const now = new Date(0)
+    now.setFullYear(14, 8 /* Sep */, 25)
+    now.setHours(0, 0, 0, 0)
+    const clock = sinon.useFakeTimers(now.getTime())
+
+    const expectedResult = new Date(0)
+    expectedResult.setFullYear(14, 8 /* Sep */, 24)
+    expectedResult.setHours(0, 0, 0, 0)
+    const result = startOfYesterday()
+    assert.deepEqual(result, expectedResult)
+
+    clock.restore()
+  })
+})