diff --git a/genrule/genrule_test.go b/genrule/genrule_test.go
new file mode 100644
index 0000000..0d690d4
--- /dev/null
+++ b/genrule/genrule_test.go
@@ -0,0 +1,374 @@
+// 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 genrule
+
+import (
+	"io/ioutil"
+	"os"
+	"strings"
+	"testing"
+
+	"android/soong/android"
+)
+
+var buildDir string
+
+func setUp() {
+	var err error
+	buildDir, err = ioutil.TempDir("", "soong_java_test")
+	if err != nil {
+		panic(err)
+	}
+}
+
+func tearDown() {
+	os.RemoveAll(buildDir)
+}
+
+func TestMain(m *testing.M) {
+	run := func() int {
+		setUp()
+		defer tearDown()
+
+		return m.Run()
+	}
+
+	os.Exit(run())
+}
+
+func testContext(config android.Config, bp string,
+	fs map[string][]byte) *android.TestContext {
+
+	ctx := android.NewTestArchContext()
+	ctx.RegisterModuleType("filegroup", android.ModuleFactoryAdaptor(android.FileGroupFactory))
+	ctx.RegisterModuleType("genrule", android.ModuleFactoryAdaptor(GenRuleFactory))
+	ctx.RegisterModuleType("tool", android.ModuleFactoryAdaptor(toolFactory))
+	ctx.Register()
+
+	bp += `
+		tool {
+			name: "tool",
+		}
+
+		filegroup {
+			name: "tool_files",
+			srcs: [
+				"tool_file1",
+				"tool_file2",
+			],
+		}
+
+		filegroup {
+			name: "1tool_file",
+			srcs: [
+				"tool_file1",
+			],
+		}
+
+		filegroup {
+			name: "ins",
+			srcs: [
+				"in1",
+				"in2",
+			],
+		}
+
+		filegroup {
+			name: "1in",
+			srcs: [
+				"in1",
+			],
+		}
+
+		filegroup {
+			name: "empty",
+		}
+	`
+
+	mockFS := map[string][]byte{
+		"Android.bp": []byte(bp),
+		"tool":       nil,
+		"tool_file1": nil,
+		"tool_file2": nil,
+		"in1":        nil,
+		"in2":        nil,
+	}
+
+	for k, v := range fs {
+		mockFS[k] = v
+	}
+
+	ctx.MockFileSystem(mockFS)
+
+	return ctx
+}
+
+func TestGenruleCmd(t *testing.T) {
+	testcases := []struct {
+		name string
+		prop string
+
+		err    string
+		expect string
+	}{
+		{
+			name: "empty location tool",
+			prop: `
+				tools: ["tool"],
+				out: ["out"],
+				cmd: "$(location) > $(out)",
+			`,
+			expect: "out/tool > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "empty location tool file",
+			prop: `
+				tool_files: ["tool_file1"],
+				out: ["out"],
+				cmd: "$(location) > $(out)",
+			`,
+			expect: "tool_file1 > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "empty location tool file fg",
+			prop: `
+				tool_files: [":1tool_file"],
+				out: ["out"],
+				cmd: "$(location) > $(out)",
+			`,
+			expect: "tool_file1 > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "empty location tool and tool file",
+			prop: `
+				tools: ["tool"],
+				tool_files: ["tool_file1"],
+				out: ["out"],
+				cmd: "$(location) > $(out)",
+			`,
+			expect: "out/tool > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "tool",
+			prop: `
+				tools: ["tool"],
+				out: ["out"],
+				cmd: "$(location tool) > $(out)",
+			`,
+			expect: "out/tool > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "tool file",
+			prop: `
+				tool_files: ["tool_file1"],
+				out: ["out"],
+				cmd: "$(location tool_file1) > $(out)",
+			`,
+			expect: "tool_file1 > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "tool file fg",
+			prop: `
+				tool_files: [":1tool_file"],
+				out: ["out"],
+				cmd: "$(location tool_file1) > $(out)",
+			`,
+			expect: "tool_file1 > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "tool files",
+			prop: `
+				tool_files: [":tool_files"],
+				out: ["out"],
+				cmd: "$(location tool_file1) $(location tool_file2) > $(out)",
+			`,
+			expect: "tool_file1 tool_file2 > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "in1",
+			prop: `
+				srcs: ["in1"],
+				out: ["out"],
+				cmd: "cat $(in) > $(out)",
+			`,
+			expect: "cat ${in} > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "in1 fg",
+			prop: `
+				srcs: [":1in"],
+				out: ["out"],
+				cmd: "cat $(in) > $(out)",
+			`,
+			expect: "cat ${in} > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "ins",
+			prop: `
+				srcs: ["in1", "in2"],
+				out: ["out"],
+				cmd: "cat $(in) > $(out)",
+			`,
+			expect: "cat ${in} > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "ins fg",
+			prop: `
+				srcs: [":ins"],
+				out: ["out"],
+				cmd: "cat $(in) > $(out)",
+			`,
+			expect: "cat ${in} > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "outs",
+			prop: `
+				out: ["out", "out2"],
+				cmd: "echo foo > $(out)",
+			`,
+			expect: "echo foo > __SBOX_OUT_FILES__",
+		},
+		{
+			name: "depfile",
+			prop: `
+				out: ["out"],
+				depfile: true,
+				cmd: "echo foo > $(out) && touch $(depfile)",
+			`,
+			expect: "echo foo > __SBOX_OUT_FILES__ && touch __SBOX_DEPFILE__",
+		},
+		{
+			name: "gendir",
+			prop: `
+				out: ["out"],
+				cmd: "echo foo > $(genDir)/foo && cp $(genDir)/foo $(out)",
+			`,
+			expect: "echo foo > __SBOX_OUT_DIR__/foo && cp __SBOX_OUT_DIR__/foo __SBOX_OUT_FILES__",
+		},
+
+		{
+			name: "error empty location",
+			prop: `
+				out: ["out"],
+				cmd: "$(location) > $(out)",
+			`,
+			err: "at least one `tools` or `tool_files` is required if $(location) is used",
+		},
+		{
+			name: "error location",
+			prop: `
+				out: ["out"],
+				cmd: "echo foo > $(location missing)",
+			`,
+			err: `unknown location label "missing"`,
+		},
+		{
+			name: "error variable",
+			prop: `
+					out: ["out"],
+					srcs: ["in1"],
+					cmd: "echo $(foo) > $(out)",
+			`,
+			err: `unknown variable '$(foo)'`,
+		},
+		{
+			name: "error depfile",
+			prop: `
+				out: ["out"],
+				cmd: "echo foo > $(out) && touch $(depfile)",
+			`,
+			err: "$(depfile) used without depfile property",
+		},
+		{
+			name: "error no depfile",
+			prop: `
+				out: ["out"],
+				depfile: true,
+				cmd: "echo foo > $(out)",
+			`,
+			err: "specified depfile=true but did not include a reference to '${depfile}' in cmd",
+		},
+		{
+			name: "error no out",
+			prop: `
+				cmd: "echo foo > $(out)",
+			`,
+			err: "must have at least one output file",
+		},
+	}
+
+	for _, test := range testcases {
+		t.Run(test.name, func(t *testing.T) {
+			config := android.TestArchConfig(buildDir, nil)
+			bp := "genrule {\n"
+			bp += "name: \"gen\",\n"
+			bp += test.prop
+			bp += "}\n"
+
+			ctx := testContext(config, bp, nil)
+
+			_, errs := ctx.ParseFileList(".", []string{"Android.bp"})
+			if errs == nil {
+				_, errs = ctx.PrepareBuildActions(config)
+			}
+			if errs == nil && test.err != "" {
+				t.Fatalf("want error %q, got no error", test.err)
+			} else if errs != nil && test.err == "" {
+				android.FailIfErrored(t, errs)
+			} else if test.err != "" {
+				if len(errs) != 1 {
+					t.Errorf("want 1 error, got %d errors:", len(errs))
+					for _, err := range errs {
+						t.Errorf("   %s", err.Error())
+					}
+					t.FailNow()
+				}
+				if !strings.Contains(errs[0].Error(), test.err) {
+					t.Fatalf("want %q, got %q", test.err, errs[0].Error())
+				}
+				return
+			}
+
+			gen := ctx.ModuleForTests("gen", "").Module().(*Module)
+			if gen.rawCommand != "'"+test.expect+"'" {
+				t.Errorf("want %q, got %q", test.expect, gen.rawCommand)
+			}
+		})
+	}
+
+}
+
+type testTool struct {
+	android.ModuleBase
+	outputFile android.Path
+}
+
+func toolFactory() android.Module {
+	module := &testTool{}
+	android.InitAndroidArchModule(module, android.HostSupported, android.MultilibFirst)
+	return module
+}
+
+func (t *testTool) DepsMutator(ctx android.BottomUpMutatorContext) {}
+
+func (t *testTool) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	t.outputFile = android.PathForTesting("out", ctx.ModuleName())
+}
+
+func (t *testTool) HostToolPath() android.OptionalPath {
+	return android.OptionalPathForPath(t.outputFile)
+}
+
+var _ HostToolProvider = (*testTool)(nil)