diff --git a/shared/paths_test.go b/shared/paths_test.go
new file mode 100644
index 0000000..018d55f
--- /dev/null
+++ b/shared/paths_test.go
@@ -0,0 +1,32 @@
+// Copyright 2021 Google Inc. All rights reserved.
+//
+// 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 shared
+
+import (
+	"testing"
+)
+
+func assertEqual(t *testing.T, expected, actual string) {
+	t.Helper()
+	if expected != actual {
+		t.Errorf("expected %q != got %q", expected, actual)
+	}
+}
+
+func TestJoinPath(t *testing.T) {
+	assertEqual(t, "/a/b", JoinPath("c/d", "/a/b"))
+	assertEqual(t, "a/b", JoinPath("a", "b"))
+	assertEqual(t, "/a/b", JoinPath("x", "/a", "b"))
+}