diff --git a/gulpfile.js b/gulpfile.js
index 4588a9fdc..cb349583a 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -26,7 +26,7 @@ var tsProject = ts.createProject(TSC_OPTIONS);
 
 gulp.task('test.check-format', function() {
   return gulp.src(['*.js', 'src/**/*.ts', 'test/**/*.ts'])
-      .pipe(formatter.checkFormat('file', clangFormat))
+      .pipe(formatter.checkFormat('file', clangFormat, {verbose: true}))
       .on('warning', onError);
 });
 
@@ -73,15 +73,24 @@ gulp.task('test.unit', ['test.compile'], function(done) {
     done();
     return;
   }
-  return gulp.src('build/test/**/*.js').pipe(mocha({timeout: 500}));
+  return gulp.src(['build/test/**/*.js', '!build/test/**/e2e*.js']).pipe(mocha({timeout: 1000}));
 });
 
-gulp.task('test', ['test.unit', 'test.check-format']);
+gulp.task('test.e2e', ['test.compile'], function(done) {
+  if (hasError) {
+    done();
+    return;
+  }
+  return gulp.src(['build/test/**/e2e*.js']).pipe(mocha({timeout: 10000}));
+});
+
+gulp.task('test', ['test.unit', 'test.e2e', 'test.check-format']);
 
-gulp.task('watch', ['test.unit'], function() {
+gulp.task('watch', ['test.unit', 'test.check-format'], function() {
   failOnError = false;
   // Avoid watching generated .d.ts in the build (aka output) directory.
-  return gulp.watch(['src/**/*.ts', 'test/**/*.ts'], {ignoreInitial: true}, ['test.unit']);
+  return gulp.watch(
+      ['src/**/*.ts', 'test/**/*.ts', 'test_files/**'], {ignoreInitial: true}, ['test.unit']);
 });
 
 gulp.task('default', ['compile']);
diff --git a/package.json b/package.json
index a8b7ece67..2e168c460 100644
--- a/package.json
+++ b/package.json
@@ -9,13 +9,14 @@
   "dependencies": {
     "source-map": "^0.4.2",
     "source-map-support": "^0.3.1",
-    "typescript": "Microsoft/TypeScript"
+    "typescript": "^1.6.2"
   },
   "devDependencies": {
     "chai": "^2.1.1",
-    "clang-format": "1.0.30",
+    "clang-format": "^1.0.32",
+    "closure-compiler": "^0.2.12",
     "gulp": "^3.8.11",
-    "gulp-clang-format": "^1.0.21",
+    "gulp-clang-format": "^1.0.22",
     "gulp-mocha": "^2.0.0",
     "gulp-sourcemaps": "^1.5.0",
     "gulp-typescript": "^2.7.6",
diff --git a/src/sickle.ts b/src/sickle.ts
index e4265080e..5731b3391 100644
--- a/src/sickle.ts
+++ b/src/sickle.ts
@@ -14,10 +14,12 @@ export function formatDiagnostics(diags: ts.Diagnostic[]): string {
       .join('\n');
 }
 
-export type AnnotatedProgram = {
+export type StringMap = {
   [fileName: string]: string
 };
 
+export type AnnotatedProgram = StringMap;
+
 /**
  * A source processor that takes TypeScript code and annotates the output with Closure-style JSDoc
  * comments.
@@ -27,7 +29,7 @@ class Annotator {
 
   constructor() {}
 
-  transform(args: string[]): AnnotatedProgram {
+  annotate(args: string[]): AnnotatedProgram {
     let tsArgs = ts.parseCommandLine(args);
     if (tsArgs.errors) {
       this.fail(formatDiagnostics(tsArgs.errors));
@@ -35,10 +37,10 @@ class Annotator {
     let program = ts.createProgram(tsArgs.fileNames, tsArgs.options);
     let diags = ts.getPreEmitDiagnostics(program);
     if (diags && diags.length) this.fail(formatDiagnostics(diags));
-    return this.transformProgram(program);
+    return this.annotateProgram(program);
   }
 
-  transformProgram(program: ts.Program): AnnotatedProgram {
+  annotateProgram(program: ts.Program): AnnotatedProgram {
     let res: AnnotatedProgram = {};
     for (let sf of program.getSourceFiles()) {
       if (sf.fileName.match(/\.d\.ts$/)) continue;
@@ -136,13 +138,13 @@ function last<T>(elems: T[]): T {
   return elems.length ? elems[elems.length - 1] : null;
 }
 
-export function transformProgram(program: ts.Program): AnnotatedProgram {
-  return new Annotator().transformProgram(program);
+export function annotateProgram(program: ts.Program): AnnotatedProgram {
+  return new Annotator().annotateProgram(program);
 }
 
 // CLI entry point
 if (require.main === module) {
-  let res = new Annotator().transform(process.argv);
+  let res = new Annotator().annotate(process.argv);
   // TODO(martinprobst): Do something useful here...
   console.log(JSON.stringify(res));
 }
diff --git a/test/closure-compiler.d.ts b/test/closure-compiler.d.ts
new file mode 100644
index 000000000..096d55cae
--- /dev/null
+++ b/test/closure-compiler.d.ts
@@ -0,0 +1,5 @@
+declare module 'closure-compiler' {
+  export interface CompileOptions { [k: string]: boolean | string | string[]; }
+  type Callback = (err: Error, stdout: string, stderr: string) => void;
+  function compile(src: string, options?: CompileOptions | Callback, callback?: Callback): void;
+}
diff --git a/test/e2e_test.ts b/test/e2e_test.ts
new file mode 100644
index 000000000..547198ccc
--- /dev/null
+++ b/test/e2e_test.ts
@@ -0,0 +1,33 @@
+import * as fs from 'fs';
+import * as path from 'path';
+import * as ts from 'typescript';
+import {expect} from 'chai';
+import {CompileOptions, compile} from 'closure-compiler';
+
+import {annotateProgram, formatDiagnostics} from '../src/sickle';
+import {goldenTests} from './test_support';
+
+export function checkClosureCompile(jsFiles: string[], done: (err: Error) => void) {
+  var startTime = Date.now();
+  var total = jsFiles.length;
+  if (!total) throw new Error('No JS files in ' + JSON.stringify(jsFiles));
+
+  var CLOSURE_COMPILER_OPTS: CompileOptions = {
+    'checks-only': true,
+    'jscomp_error': 'checkTypes',
+    'js': jsFiles,
+    'language_in': 'ECMASCRIPT6'
+  };
+
+  compile(null, CLOSURE_COMPILER_OPTS, (err, stdout, stderr) => {
+    console.log('Closure compilation:', total, 'done after', Date.now() - startTime, 'ms');
+    done(err);
+  });
+}
+
+describe('golden file tests', () => {
+  it('generates correct Closure code', (done: (err: Error) => void) => {
+    var goldenJs = goldenTests().map((t) => t.jsPath);
+    checkClosureCompile(goldenJs, done);
+  });
+});
diff --git a/test/sickle_test.ts b/test/sickle_test.ts
index 65b87cc2a..87d50d758 100644
--- a/test/sickle_test.ts
+++ b/test/sickle_test.ts
@@ -1,64 +1,15 @@
-import {expect} from 'chai';
+import * as fs from 'fs';
+import * as path from 'path';
 import * as ts from 'typescript';
+import {expect} from 'chai';
 
-import {transformProgram, formatDiagnostics} from '../src/sickle';
-
-const OPTIONS: ts.CompilerOptions = {
-  noImplicitAny: true,
-  noResolve: true,
-  skipDefaultLibCheck: true,
-};
-
-const {cachedLibName, cachedLib} = (function() {
-  let host = ts.createCompilerHost(OPTIONS);
-  let fn = host.getDefaultLibFileName(OPTIONS);
-  return {cachedLibName: fn, cachedLib: host.getSourceFile(fn, ts.ScriptTarget.ES6)};
-})();
-
-function transformSource(src: string): string {
-  var host = ts.createCompilerHost(OPTIONS);
-  var original = host.getSourceFile.bind(host);
-  host.getSourceFile = function(fileName: string, languageVersion: ts.ScriptTarget,
-                                onError?: (msg: string) => void): ts.SourceFile {
-    if (fileName === cachedLibName) return cachedLib;
-    if (fileName === 'main.ts') {
-      return ts.createSourceFile(fileName, src, ts.ScriptTarget.Latest, true);
-    }
-    return original(fileName, languageVersion, onError);
-  };
-
-  var program = ts.createProgram(['main.ts'], {}, host);
-  if (program.getSyntacticDiagnostics().length) {
-    throw new Error(formatDiagnostics(ts.getPreEmitDiagnostics(program)));
-  }
-
-  var res = transformProgram(program);
-  expect(Object.keys(res)).to.deep.equal(['main.ts']);
-  return res['main.ts'];
-}
-
-function expectSource(src: string) {
-  return expect(transformSource(src));
-}
+import {annotateProgram, formatDiagnostics} from '../src/sickle';
+import {expectSource, goldenTests} from './test_support';
 
-describe('adding JSDoc types', () => {
-  it('handles variable declarations', () => {
-    expectSource('var x: string;').to.equal('var /** string */ x: string;');
-    expectSource('var x: string, y: number;')
-        .to.equal('var /** string */ x: string, /** number */ y: number;');
-  });
-  it('handles function declarations', () => {
-    expectSource('function x(a: number): string {\n' +
-                 '  return "a";\n' +
-                 '}')
-        .to.equal(' /** @return { string} */function x( /** number */a: number): string {\n' +
-                  '  return "a";\n' +
-                  '}');
-    expectSource('function x(a: number, b: number) {}')
-        .to.equal('function x( /** number */a: number, /** number */ b: number) {}');
-  });
-  it('handles arrow functions', () => {
-    expectSource('var x = (a: number): number => 12;')
-        .to.equal('var x = /** @return { number} */ ( /** number */a: number): number => 12;');
+describe('golden tests', () => {
+  goldenTests().forEach((test) => {
+    var tsSource = fs.readFileSync(test.tsPath, 'utf-8');
+    var jsSource = fs.readFileSync(test.jsPath, 'utf-8');
+    it(test.name, () => { expectSource(tsSource).to.equal(jsSource); });
   });
 });
diff --git a/test/test_support.ts b/test/test_support.ts
index 2d6bdde49..c15ae98ca 100644
--- a/test/test_support.ts
+++ b/test/test_support.ts
@@ -1,42 +1,98 @@
 import {expect} from 'chai';
 import * as ts from 'typescript';
+import * as fs from 'fs';
+import * as path from 'path';
 
-import {transformProgram, formatDiagnostics} from '../src/sickle';
+import {annotateProgram, formatDiagnostics, StringMap} from '../src/sickle';
 
 const OPTIONS: ts.CompilerOptions = {
+  target: ts.ScriptTarget.ES6,
   noImplicitAny: true,
   noResolve: true,
   skipDefaultLibCheck: true,
 };
 
-const {cachedLibName, cachedLib} = (function() {
+const {cachedLibPath, cachedLib} = (function() {
   let host = ts.createCompilerHost(OPTIONS);
   let fn = host.getDefaultLibFileName(OPTIONS);
-  return {cachedLibName: fn, cachedLib: host.getSourceFile(fn, ts.ScriptTarget.ES6)};
+  let p = ts.getDefaultLibFilePath(OPTIONS);
+  return {cachedLibPath: p, cachedLib: host.getSourceFile(fn, ts.ScriptTarget.ES6)};
 })();
 
-function transformSource(src: string): string {
+function annotateSource(src: string): string {
   var host = ts.createCompilerHost(OPTIONS);
   var original = host.getSourceFile.bind(host);
-  host.getSourceFile = function(fileName: string, languageVersion: ts.ScriptTarget,
-                                onError?: (msg: string) => void): ts.SourceFile {
-    if (fileName === cachedLibName) return cachedLib;
+  host.getSourceFile = function(
+                           fileName: string, languageVersion: ts.ScriptTarget,
+                           onError?: (msg: string) => void): ts.SourceFile {
+    if (fileName === cachedLibPath) return cachedLib;
     if (fileName === 'main.ts') {
       return ts.createSourceFile(fileName, src, ts.ScriptTarget.Latest, true);
     }
     return original(fileName, languageVersion, onError);
   };
 
-  var program = ts.createProgram(['main.ts'], {}, host);
+  var program = ts.createProgram(['main.ts'], OPTIONS, host);
   if (program.getSyntacticDiagnostics().length) {
     throw new Error(formatDiagnostics(ts.getPreEmitDiagnostics(program)));
   }
 
-  var res = transformProgram(program);
+  var res = annotateProgram(program);
   expect(Object.keys(res)).to.deep.equal(['main.ts']);
   return res['main.ts'];
 }
 
+function transformSource(src: string): string {
+  var host = ts.createCompilerHost(OPTIONS);
+  var original = host.getSourceFile.bind(host);
+  var mainSrc = ts.createSourceFile('main.ts', src, ts.ScriptTarget.Latest, true);
+  host.getSourceFile = function(
+                           fileName: string, languageVersion: ts.ScriptTarget,
+                           onError?: (msg: string) => void): ts.SourceFile {
+    if (fileName === cachedLibPath) return cachedLib;
+    if (fileName === 'main.ts') {
+      return mainSrc;
+    }
+    return original(fileName, languageVersion, onError);
+  };
+
+  var program = ts.createProgram(['main.ts'], OPTIONS, host);
+  if (program.getSyntacticDiagnostics().length) {
+    throw new Error(formatDiagnostics(ts.getPreEmitDiagnostics(program)));
+  }
+
+  var transformed: StringMap = {};
+  var emitRes =
+      program.emit(mainSrc, (fileName: string, data: string) => { transformed[fileName] = data; });
+  if (emitRes.diagnostics.length) {
+    throw new Error(formatDiagnostics(emitRes.diagnostics));
+  }
+  expect(Object.keys(transformed)).to.deep.equal(['main.js']);
+  return transformed['main.js'];
+}
+
 export function expectSource(src: string) {
-  return expect(transformSource(src));
+  var annotated = annotateSource(src);
+  // console.log('Annotated', annotated);
+  var transformed = transformSource(annotated);
+  return expect(transformed);
+}
+
+export interface GoldenFileTest {
+  name: string;
+  tsPath: string;
+  jsPath: string;
+}
+
+export function goldenTests(): GoldenFileTest[] {
+  var tsExtRe = /\.ts$/;
+  var testFolder = path.join(__dirname, '..', '..', 'test_files');
+  var files = fs.readdirSync(testFolder).filter((fn) => !!fn.match(tsExtRe));
+  return files.map((fn) => {
+    return {
+      name: fn,
+      tsPath: path.join(testFolder, fn),
+      jsPath: path.join(testFolder, fn.replace(tsExtRe, '.js')),
+    };
+  });
 }
diff --git a/test_files/arrow_fn.js b/test_files/arrow_fn.js
new file mode 100644
index 000000000..6a9e76003
--- /dev/null
+++ b/test_files/arrow_fn.js
@@ -0,0 +1 @@
+var fn3 = (/** number */ a) => 12;
diff --git a/test_files/arrow_fn.ts b/test_files/arrow_fn.ts
new file mode 100644
index 000000000..9ba372ea8
--- /dev/null
+++ b/test_files/arrow_fn.ts
@@ -0,0 +1 @@
+var fn3 = (a: number): number => 12;
diff --git a/test_files/functions.js b/test_files/functions.js
new file mode 100644
index 000000000..c11b2a462
--- /dev/null
+++ b/test_files/functions.js
@@ -0,0 +1,4 @@
+/** @return { string} */ function fn1(/** number */ a) {
+    return "a";
+}
+function fn2(/** number */ a, /** number */ b) { }
diff --git a/test_files/functions.ts b/test_files/functions.ts
new file mode 100644
index 000000000..7484cba48
--- /dev/null
+++ b/test_files/functions.ts
@@ -0,0 +1,4 @@
+function fn1(a: number): string {
+  return "a";
+}
+function fn2(a: number, b: number) {}
diff --git a/test_files/variables.js b/test_files/variables.js
new file mode 100644
index 000000000..a05a0b9e8
--- /dev/null
+++ b/test_files/variables.js
@@ -0,0 +1,2 @@
+var /** string */ v1;
+var /** string */ v2, /** number */ v3;
diff --git a/test_files/variables.ts b/test_files/variables.ts
new file mode 100644
index 000000000..648ac0a33
--- /dev/null
+++ b/test_files/variables.ts
@@ -0,0 +1,2 @@
+var v1: string;
+var v2: string, v3: number;
diff --git a/tsconfig.json b/tsconfig.json
index 43ab3564d..e722047b4 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -7,6 +7,7 @@
   "files": [
     "src/sickle.ts",
     "test/sickle_test.ts",
+    "test/closure-compiler.d.ts",
     "typings/tsd.d.ts"
   ]
 }