diff --git a/cc/util_test.go b/cc/util_test.go
new file mode 100644
index 0000000..3108294
--- /dev/null
+++ b/cc/util_test.go
@@ -0,0 +1,68 @@
+// Copyright 2018 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 cc
+
+import (
+	"testing"
+)
+
+func TestSplitFileExt(t *testing.T) {
+	t.Run("soname with version", func(t *testing.T) {
+		root, suffix, ext := splitFileExt("libtest.so.1.0.30")
+		expected := "libtest"
+		if root != expected {
+			t.Errorf("root should be %q but got %q", expected, root)
+		}
+		expected = ".so.1.0.30"
+		if suffix != expected {
+			t.Errorf("suffix should be %q but got %q", expected, suffix)
+		}
+		expected = ".so"
+		if ext != expected {
+			t.Errorf("ext should be %q but got %q", expected, ext)
+		}
+	})
+
+	t.Run("version numbers in the middle should be ignored", func(t *testing.T) {
+		root, suffix, ext := splitFileExt("libtest.1.0.30.so")
+		expected := "libtest.1.0.30"
+		if root != expected {
+			t.Errorf("root should be %q but got %q", expected, root)
+		}
+		expected = ".so"
+		if suffix != expected {
+			t.Errorf("suffix should be %q but got %q", expected, suffix)
+		}
+		expected = ".so"
+		if ext != expected {
+			t.Errorf("ext should be %q but got %q", expected, ext)
+		}
+	})
+
+	t.Run("no known file extension", func(t *testing.T) {
+		root, suffix, ext := splitFileExt("test.exe")
+		expected := "test"
+		if root != expected {
+			t.Errorf("root should be %q but got %q", expected, root)
+		}
+		expected = ".exe"
+		if suffix != expected {
+			t.Errorf("suffix should be %q but got %q", expected, suffix)
+		}
+		if ext != expected {
+			t.Errorf("ext should be %q but got %q", expected, ext)
+		}
+	})
+}