add testing logger

log/testing_logger.go

@@ -0,0 +1,31 @@
+package log
+
+import (
+	"os"
+	"testing"
+)
+
+var (
+	// reuse the same logger across all tests
+	_testingLogger Logger
+)
+
+// TestingLogger returns a TMLogger which writes to STDOUT if testing being run
+// with the verbose (-v) flag, NopLogger otherwise.
+//
+// Note that the call to TestingLogger() must be made
+// inside a test (not in the init func) because
+// verbose flag only set at the time of testing.
+func TestingLogger() Logger {
+	if _testingLogger != nil {
+		return _testingLogger
+	}
+
+	if testing.Verbose() {
+		_testingLogger = NewTMLogger(os.Stdout)
+	} else {
+		_testingLogger = NewNopLogger()
+	}
+
+	return _testingLogger
+}