Avoid test flags in normal binary.

Change-Id: If1fba813a73bf93ea5918dcda326e3ffa81a797d

storage/local/test_helpers.go

@@ -11,10 +11,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// NOTE ON FILENAME: Do not rename this file helpers_test.go (which might appear
+// an obvious choice). We need NewTestStorage in tests outside of the local
+// package, too. On the other hand, moving NewTestStorage in its own package
+// would cause circular dependencies in the tests in packages local.
+
 package local
 
 import (
-	"testing"
 	"time"
 
 	"github.com/prometheus/prometheus/utility/test"
@@ -33,7 +37,7 @@ func (t *testStorageCloser) Close() {
 // NewTestStorage creates a storage instance backed by files in a temporary
 // directory. The returned storage is already in serving state. Upon closing the
 // returned test.Closer, the temporary directory is cleaned up.
-func NewTestStorage(t testing.TB) (Storage, test.Closer) {
+func NewTestStorage(t test.T) (Storage, test.Closer) {
 	directory := test.NewTemporaryDirectory("test_storage", t)
 	o := &MemorySeriesStorageOptions{
 		MemoryChunks:               1000000,

utility/test/directory.go

@@ -16,7 +16,6 @@ package test
 import (
 	"io/ioutil"
 	"os"
-	"testing"
 )
 
 const (
@@ -51,12 +50,21 @@ type (
 	// their interactions.
 	temporaryDirectory struct {
 		path   string
-		tester testing.TB
+		tester T
 	}
 
 	callbackCloser struct {
 		fn func()
 	}
+
+	// T implements the needed methods of testing.TB so that we do not need
+	// to actually import testing (which has the side affect of adding all
+	// the test flags, which we do not want in non-test binaries even if
+	// they make use of these utilities for some reason).
+	T interface {
+		Fatal(args ...interface{})
+		Fatalf(format string, args ...interface{})
+	}
 )
 
 func (c nilCloser) Close() {
@@ -90,7 +98,7 @@ func (t temporaryDirectory) Path() string {
 
 // NewTemporaryDirectory creates a new temporary directory for transient POSIX
 // activities.
-func NewTemporaryDirectory(name string, t testing.TB) (handler TemporaryDirectory) {
+func NewTemporaryDirectory(name string, t T) (handler TemporaryDirectory) {
 	var (
 		directory string
 		err       error