diff --git a/prometheus/counter_test.go b/prometheus/counter_test.go
index 8f0dffd..b430e5e 100644
--- a/prometheus/counter_test.go
+++ b/prometheus/counter_test.go
@@ -9,9 +9,11 @@ package prometheus
 import (
 	"encoding/json"
 	"testing"
+
+	"github.com/prometheus/client_golang/test"
 )
 
-func testCounter(t tester) {
+func testCounter(t test.Tester) {
 	type input struct {
 		steps []func(g Counter)
 	}
diff --git a/prometheus/gauge_test.go b/prometheus/gauge_test.go
index 1380ad7..9346694 100644
--- a/prometheus/gauge_test.go
+++ b/prometheus/gauge_test.go
@@ -9,9 +9,11 @@ package prometheus
 import (
 	"encoding/json"
 	"testing"
+
+	"github.com/prometheus/client_golang/test"
 )
 
-func testGauge(t tester) {
+func testGauge(t test.Tester) {
 	type input struct {
 		steps []func(g Gauge)
 	}
diff --git a/prometheus/interface.go b/prometheus/interface.go
deleted file mode 100644
index 9b5de19..0000000
--- a/prometheus/interface.go
+++ /dev/null
@@ -1,14 +0,0 @@
-// Copyright (c) 2013, Prometheus Team
-// All rights reserved.
-//
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package prometheus
-
-type tester interface {
-	Error(args ...interface{})
-	Errorf(format string, args ...interface{})
-	Fatal(args ...interface{})
-	Fatalf(format string, args ...interface{})
-}
diff --git a/prometheus/registry_test.go b/prometheus/registry_test.go
index b153822..85cab7c 100644
--- a/prometheus/registry_test.go
+++ b/prometheus/registry_test.go
@@ -20,9 +20,10 @@ import (
 	"code.google.com/p/goprotobuf/proto"
 
 	"github.com/prometheus/client_golang/model"
+	"github.com/prometheus/client_golang/test"
 )
 
-func testRegister(t tester) {
+func testRegister(t test.Tester) {
 	var oldState = struct {
 		abortOnMisuse             bool
 		debugRegistration         bool
@@ -205,7 +206,7 @@ func (r *fakeResponseWriter) Write(d []byte) (l int, err error) {
 func (r *fakeResponseWriter) WriteHeader(c int) {
 }
 
-func testHandler(t tester) {
+func testHandler(t test.Tester) {
 
 	metric := NewCounter()
 	metric.Increment(map[string]string{"labelname": "val1"})
@@ -484,7 +485,7 @@ func BenchmarkHandler(b *testing.B) {
 	}
 }
 
-func testDecorateWriter(t tester) {
+func testDecorateWriter(t test.Tester) {
 	type input struct {
 		headers map[string]string
 		body    []byte
@@ -569,7 +570,7 @@ func BenchmarkDecorateWriter(b *testing.B) {
 	}
 }
 
-func testDumpToWriter(t tester) {
+func testDumpToWriter(t test.Tester) {
 	type input struct {
 		metrics map[string]Metric
 	}
diff --git a/prometheus/untyped_test.go b/prometheus/untyped_test.go
index f39cd87..b2a2b57 100644
--- a/prometheus/untyped_test.go
+++ b/prometheus/untyped_test.go
@@ -9,9 +9,11 @@ package prometheus
 import (
 	"encoding/json"
 	"testing"
+
+	"github.com/prometheus/client_golang/test"
 )
 
-func testUntyped(t tester) {
+func testUntyped(t test.Tester) {
 	type input struct {
 		steps []func(g Untyped)
 	}
diff --git a/test/test.go b/test/test.go
index 225aa70..a4440aa 100644
--- a/test/test.go
+++ b/test/test.go
@@ -14,6 +14,7 @@
 // Package test provides common test helpers to the client library.
 package test
 
+// Tester is an interface implemented by both, testing.T and testing.B.
 type Tester interface {
 	Error(args ...interface{})
 	Errorf(format string, args ...interface{})