diff --git a/api/test/metrics/metric.cc b/api/test/metrics/metric.cc
new file mode 100644
index 0000000..7bace78d
--- /dev/null
+++ b/api/test/metrics/metric.cc
@@ -0,0 +1,48 @@
+/*
+ *  Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+#include "api/test/metrics/metric.h"
+
+#include <string>
+
+namespace webrtc {
+namespace test {
+
+absl::string_view ToString(Unit unit) {
+  switch (unit) {
+    case Unit::kTimeMs:
+      return "TimeMs";
+    case Unit::kPercent:
+      return "Percent";
+    case Unit::kSizeInBytes:
+      return "SizeInBytes";
+    case Unit::kKilobitsPerSecond:
+      return "KilobitsPerSecond";
+    case Unit::kHertz:
+      return "Hertz";
+    case Unit::kUnitless:
+      return "Unitless";
+    case Unit::kCount:
+      return "Count";
+  }
+}
+
+absl::string_view ToString(ImprovementDirection direction) {
+  switch (direction) {
+    case ImprovementDirection::kBiggerIsBetter:
+      return "BiggerIsBetter";
+    case ImprovementDirection::kNeitherIsBetter:
+      return "NeitherIsBetter";
+    case ImprovementDirection::kSmallerIsBetter:
+      return "SmallerIsBetter";
+  }
+}
+
+}  // namespace test
+}  // namespace webrtc