Improve testutil.ErrorEqual (#6471)

Also improves TestPopulateLabels: testutil.ErrorEqual just returned a
bool without failing the test.

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

scrape/manager_test.go

@@ -215,7 +215,7 @@ func TestPopulateLabels(t *testing.T) {
 		in := c.in.Copy()
 
 		res, orig, err := populateLabels(c.in, c.cfg)
-		testutil.ErrorEqual(err, c.err)
+		testutil.ErrorEqual(t, c.err, err)
 		testutil.Equals(t, c.in, in)
 		testutil.Equals(t, c.res, res)
 		testutil.Equals(t, c.resOrig, orig)

storage/remote/client_test.go

@@ -75,9 +75,7 @@ func TestStoreHTTPErrorHandling(t *testing.T) {
 		testutil.Ok(t, err)
 
 		err = c.Store(context.Background(), []byte{})
-		if !testutil.ErrorEqual(err, test.err) {
-			t.Errorf("%d. Unexpected error; want %v, got %v", i, test.err, err)
-		}
+		testutil.ErrorEqual(t, err, test.err, "unexpected error in test %d", i)
 
 		server.Close()
 	}

util/testutil/error.go

@@ -1,27 +0,0 @@
-// Copyright 2013 The Prometheus Authors
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package testutil
-
-// ErrorEqual compares Go errors for equality.
-func ErrorEqual(left, right error) bool {
-	if left == right {
-		return true
-	}
-
-	if left != nil && right != nil {
-		return left.Error() == right.Error()
-	}
-
-	return false
-}

util/testutil/testing.go

@@ -71,6 +71,21 @@ func Equals(tb TB, exp, act interface{}, msgAndArgs ...interface{}) {
 	}
 }
 
+// ErrorEqual compares Go errors for equality.
+func ErrorEqual(tb TB, left, right error, msgAndArgs ...interface{}) {
+	tb.Helper()
+	if left == right {
+		return
+	}
+
+	if left != nil && right != nil {
+		Equals(tb, left.Error(), right.Error(), msgAndArgs...)
+		return
+	}
+
+	tb.Fatalf("\033[31m%s\n\nexp: %#v\n\ngot: %#v\033[39m\n", formatMessage(msgAndArgs), left, right)
+}
+
 func formatMessage(msgAndArgs []interface{}) string {
 	if len(msgAndArgs) == 0 {
 		return ""