Merge pull request #9 from xmidt-org/feature/check-system-clock

Feature/check system clock

CHANGELOG.md

@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+- IsSystemClock for verifying production code initialization
 
 ## [v0.1.0]
 - basic examples

systemClock.go

@@ -87,3 +87,11 @@ func (sc systemClock) NewTimer(d time.Duration) Timer {
 func SystemClock() Clock {
 	return systemClock{}
 }
+
+// IsSystemClock tests if c is actually a Clock returned by SystemClock().
+// This function is primarily useful in test code to verify that production
+// code correctly initializes itself.
+func IsSystemClock(c Clock) bool {
+	_, ok := c.(systemClock)
+	return ok
+}

systemClock_test.go

@@ -117,6 +117,16 @@ func (suite *SystemClockSuite) TestNewTicker() {
 	suite.requireSignal(t.C(), 16*time.Millisecond)
 }
 
+func (suite *SystemClockSuite) TestIsSystemClock() {
+	suite.True(
+		IsSystemClock(SystemClock()),
+	)
+
+	suite.False(
+		IsSystemClock(NewFakeClock(time.Now())),
+	)
+}
+
 func TestSystemClock(t *testing.T) {
 	suite.Run(t, new(SystemClockSuite))
 }