fixup! k6runner/test: ensure logs are sent to loki when runner report…

…s user errors

internal/k6runner/k6runner_test.go

@@ -307,7 +307,7 @@ func TestScriptHTTPRun(t *testing.T) {
 			var (
 				registry = prometheus.NewRegistry()
 				logBuf   = bytes.Buffer{}
-				logger   = &testLogger{buf: &logBuf}
+				logger   = recordingLogger{buf: &logBuf}
 				zlogger  = zerolog.Nop()
 			)
 
@@ -417,23 +417,30 @@ func TestK6LogsToLogger(t *testing.T) {
 	require.NoError(t, err)
 }
 
-type testLogger struct {
-	buf *bytes.Buffer
-}
+type testLogger struct{}
 
 var _ logger.Logger = &testLogger{}
 
 func (l *testLogger) Log(keyvals ...any) error {
 	if len(keyvals) == 0 {
 		return errors.New("empty log message")
 	}
+	return nil
+}
 
-	if len(keyvals)%2 != 0 {
-		return errors.New("not the same number of keys and vals")
+type recordingLogger struct {
+	buf *bytes.Buffer
+}
+
+var _ logger.Logger = &recordingLogger{}
+
+func (l recordingLogger) Log(keyvals ...any) error {
+	if len(keyvals) == 0 {
+		return errors.New("empty log message")
 	}
 
-	if l.buf == nil {
-		return nil
+	if len(keyvals)%2 != 0 {
+		return errors.New("not the same number of keys and vals")
 	}
 
 	line := make([]string, 0, len(keyvals)/2)