coder
diff --git a/‎clock/clock.go
+25 b/‎clock/clock.go
+25
@@ -0,0 +1,25 @@
+// Package clock is a library for testing time related code.  It exports an interface Clock that
+// mimics the standard library time package functions.  In production, an implementation that calls
+// thru to the standard library is used.  In testing, a Mock clock is used to precisely control and
+// intercept time functions.
+package clock
+
+import (
+	"context"
+	"time"
+)
+
+type Clock interface {
+	// TickerFunc is a convenience function that calls f on the interval d until either the given
+	// context expires or f returns an error.  Callers may call Wait() on the returned Waiter to
+	// wait until this happens and obtain the error.
+	TickerFunc(ctx context.Context, d time.Duration, f func() error, tags ...string) Waiter
+	// NewTimer creates a new Timer that will send the current time on its channel after at least
+	// duration d.
+	NewTimer(d time.Duration, tags ...string) *Timer
+}
+
+// Waiter can be waited on for an error.
+type Waiter interface {
+	Wait(tags ...string) error
+}