--- /dev/null
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//+build go1.13
+
+package xerrors_test
+
+import (
+ "errors"
+ "testing"
+
+ "golang.org/x/xerrors"
+)
+
+func TestErrorsIs(t *testing.T) {
+ var errSentinel = errors.New("sentinel")
+
+ got := errors.Is(xerrors.Errorf("%w", errSentinel), errSentinel)
+ if !got {
+ t.Error("got false, want true")
+ }
+
+ got = errors.Is(xerrors.Errorf("%w: %s", errSentinel, "foo"), errSentinel)
+ if !got {
+ t.Error("got false, want true")
+ }
+}