Extra testing for engine.Shutdown

Signed-off-by: Solomon Hykes <solomon@docker.com>

engine/shutdown_test.go

@@ -0,0 +1,80 @@
+package engine
+
+import (
+	"testing"
+	"time"
+)
+
+func TestShutdownEmpty(t *testing.T) {
+	eng := New()
+	if eng.IsShutdown() {
+		t.Fatalf("IsShutdown should be false")
+	}
+	eng.Shutdown()
+	if !eng.IsShutdown() {
+		t.Fatalf("IsShutdown should be true")
+	}
+}
+
+func TestShutdownAfterRun(t *testing.T) {
+	eng := New()
+	var called bool
+	eng.Register("foo", func(job *Job) Status {
+		called = true
+		return StatusOK
+	})
+	if err := eng.Job("foo").Run(); err != nil {
+		t.Fatal(err)
+	}
+	eng.Shutdown()
+	if err := eng.Job("foo").Run(); err == nil {
+		t.Fatalf("%#v", *eng)
+	}
+}
+
+// An approximate and racy, but better-than-nothing test that
+//
+func TestShutdownDuringRun(t *testing.T) {
+	var (
+		jobDelay     time.Duration = 500 * time.Millisecond
+		jobDelayLow  time.Duration = 100 * time.Millisecond
+		jobDelayHigh time.Duration = 700 * time.Millisecond
+	)
+	eng := New()
+	var completed bool
+	eng.Register("foo", func(job *Job) Status {
+		time.Sleep(jobDelay)
+		completed = true
+		return StatusOK
+	})
+	go eng.Job("foo").Run()
+	time.Sleep(50 * time.Millisecond)
+	done := make(chan struct{})
+	var startShutdown time.Time
+	go func() {
+		startShutdown = time.Now()
+		eng.Shutdown()
+		close(done)
+	}()
+	time.Sleep(50 * time.Millisecond)
+	if err := eng.Job("foo").Run(); err == nil {
+		t.Fatalf("run on shutdown should fail: %#v", *eng)
+	}
+	<-done
+	// Verify that Shutdown() blocks for roughly 500ms, instead
+	// of returning almost instantly.
+	//
+	// We use >100ms to leave ample margin for race conditions between
+	// goroutines. It's possible (but unlikely in reasonable testing
+	// conditions), that this test will cause a false positive or false
+	// negative. But it's probably better than not having any test
+	// for the 99.999% of time where testing conditions are reasonable.
+	if d := time.Since(startShutdown); d.Nanoseconds() < jobDelayLow.Nanoseconds() {
+		t.Fatalf("shutdown did not block long enough: %v", d)
+	} else if d.Nanoseconds() > jobDelayHigh.Nanoseconds() {
+		t.Fatalf("shutdown blocked too long: %v", d)
+	}
+	if !completed {
+		t.Fatalf("job did not complete")
+	}
+}