Add tests, fix a bug

breaker/breaker.go

@@ -88,8 +88,7 @@ func (b *Breaker) processResult(result error, panicValue interface{}) {
 		}
 	} else {
 		if b.errors > 0 {
-			expiry := b.lastError //time.Add mutates, so take a copy
-			expiry.Add(b.timeout)
+			expiry := b.lastError.Add(b.timeout)
 			if time.Now().After(expiry) {
 				b.errors = 0
 			}

breaker/breaker_test.go

@@ -0,0 +1,78 @@
+package breaker
+
+import (
+	"errors"
+	"testing"
+	"time"
+)
+
+var someError = errors.New("someError")
+
+func returnsError() error {
+	return someError
+}
+
+func returnsSuccess() error {
+	return nil
+}
+
+func TestBreakerErrorExpiry(t *testing.T) {
+	breaker := New(2, 1, 1*time.Second)
+
+	for i := 0; i < 5; i++ {
+		if err := breaker.Run(returnsError); err != someError {
+			t.Error(err)
+		}
+		time.Sleep(1 * time.Second)
+	}
+}
+
+func TestBreakerStateTransitions(t *testing.T) {
+	breaker := New(3, 2, 1*time.Second)
+
+	// three errors opens the breaker
+	for i := 0; i < 3; i++ {
+		if err := breaker.Run(returnsError); err != someError {
+			t.Error(err)
+		}
+	}
+
+	// breaker is open
+	for i := 0; i < 5; i++ {
+		if err := breaker.Run(returnsError); err != BreakerOpen {
+			t.Error(err)
+		}
+	}
+
+	// wait for it to half-close
+	time.Sleep(2 * time.Second)
+	// one success works, but is not enough to fully close
+	if err := breaker.Run(returnsSuccess); err != nil {
+		t.Error(err)
+	}
+	// error works, but re-opens immediately
+	if err := breaker.Run(returnsError); err != someError {
+		t.Error(err)
+	}
+	// breaker is open
+	if err := breaker.Run(returnsError); err != BreakerOpen {
+		t.Error(err)
+	}
+
+	// wait for it to half-close
+	time.Sleep(2 * time.Second)
+	// two successes is enough to close it for good
+	for i := 0; i < 2; i++ {
+		if err := breaker.Run(returnsSuccess); err != nil {
+			t.Error(err)
+		}
+	}
+	// error works
+	if err := breaker.Run(returnsError); err != someError {
+		t.Error(err)
+	}
+	// breaker is still closed
+	if err := breaker.Run(returnsSuccess); err != nil {
+		t.Error(err)
+	}
+}