diff --git a/android/expand_test.go b/android/expand_test.go
new file mode 100644
index 0000000..ca50b39
--- /dev/null
+++ b/android/expand_test.go
@@ -0,0 +1,153 @@
+// Copyright 2016 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 android
+
+import (
+	"fmt"
+	"testing"
+)
+
+var vars = map[string]string{
+	"var1": "abc",
+	"var2": "",
+	"var3": "def",
+	"💩":    "😃",
+}
+
+func expander(s string) (string, error) {
+	if val, ok := vars[s]; ok {
+		return val, nil
+	} else {
+		return "", fmt.Errorf("unknown variable %q", s)
+	}
+}
+
+var expandTestCases = []struct {
+	in  string
+	out string
+	err bool
+}{
+	{
+		in:  "$(var1)",
+		out: "abc",
+	},
+	{
+		in:  "$( var1 )",
+		out: "abc",
+	},
+	{
+		in:  "def$(var1)",
+		out: "defabc",
+	},
+	{
+		in:  "$(var1)def",
+		out: "abcdef",
+	},
+	{
+		in:  "def$(var1)def",
+		out: "defabcdef",
+	},
+	{
+		in:  "$(var2)",
+		out: "",
+	},
+	{
+		in:  "def$(var2)",
+		out: "def",
+	},
+	{
+		in:  "$(var2)def",
+		out: "def",
+	},
+	{
+		in:  "def$(var2)def",
+		out: "defdef",
+	},
+	{
+		in:  "$(var1)$(var3)",
+		out: "abcdef",
+	},
+	{
+		in:  "$(var1)g$(var3)",
+		out: "abcgdef",
+	},
+	{
+		in:  "$$",
+		out: "$",
+	},
+	{
+		in:  "$$(var1)",
+		out: "$(var1)",
+	},
+	{
+		in:  "$$$(var1)",
+		out: "$abc",
+	},
+	{
+		in:  "$(var1)$$",
+		out: "abc$",
+	},
+	{
+		in:  "$(💩)",
+		out: "😃",
+	},
+
+	// Errors
+	{
+		in:  "$",
+		err: true,
+	},
+	{
+		in:  "$$$",
+		err: true,
+	},
+	{
+		in:  "$(var1)$",
+		err: true,
+	},
+	{
+		in:  "$(var1)$",
+		err: true,
+	},
+	{
+		in:  "$(var4)",
+		err: true,
+	},
+	{
+		in:  "$var1",
+		err: true,
+	},
+	{
+		in:  "$(var1",
+		err: true,
+	},
+	{
+		in:  "$a💩c",
+		err: true,
+	},
+}
+
+func TestExpand(t *testing.T) {
+	for _, test := range expandTestCases {
+		got, err := Expand(test.in, expander)
+		if err != nil && !test.err {
+			t.Errorf("%q: unexpected error %s", test.in, err.Error())
+		} else if err == nil && test.err {
+			t.Errorf("%q: expected error, got %q", test.in, got)
+		} else if !test.err && got != test.out {
+			t.Errorf("%q: expected %q, got %q", test.in, test.out, got)
+		}
+	}
+}