diff --git a/modules/angular2/test/dev_mode_spec.ts b/modules/angular2/test/dev_mode_spec.ts
new file mode 100644
index 0000000000..e241e76bd8
--- /dev/null
+++ b/modules/angular2/test/dev_mode_spec.ts
@@ -0,0 +1,20 @@
+import {
+  AsyncTestCompleter,
+  beforeEach,
+  ddescribe,
+  describe,
+  expect,
+  iit,
+  inject,
+  it,
+  xdescribe,
+  xit
+} from 'angular2/testing_internal';
+
+import {assertionsEnabled} from 'angular2/src/core/facade/lang';
+
+export function main() {
+  describe('dev mode', () => {
+    it('is enabled in our tests by default', () => { expect(assertionsEnabled()).toBe(true); });
+  });
+}
diff --git a/modules/angular2/test/public_api_spec.ts b/modules/angular2/test/public_api_spec.ts
index f4cae4eda2..472220d19a 100644
--- a/modules/angular2/test/public_api_spec.ts
+++ b/modules/angular2/test/public_api_spec.ts
@@ -738,6 +738,7 @@ var NG_ALL = [
 
   'OutputMetadata',
   'OutputMetadata.bindingPropertyName',
+  'enableDevMode():js',
   'ExpressionChangedAfterItHasBeenCheckedException',
   'ExpressionChangedAfterItHasBeenCheckedException.message',
   'ExpressionChangedAfterItHasBeenCheckedException.stackTrace',
diff --git a/test-main.js b/test-main.js
index 40c4be42eb..144930c51e 100644
--- a/test-main.js
+++ b/test-main.js
@@ -18,6 +18,8 @@ System.config({
   }
 });
 
+window.angularDevMode = true;
+
 // Import all the specs, execute their `main()` method and kick off Karma (Jasmine).
 System.import('angular2/src/core/dom/browser_adapter').then(function(browser_adapter) {
   browser_adapter.BrowserDomAdapter.makeCurrent();
diff --git a/tools/broccoli/html-replace/SCRIPTS.html b/tools/broccoli/html-replace/SCRIPTS.html
index 0402ad59c7..38bd5efe0e 100644
--- a/tools/broccoli/html-replace/SCRIPTS.html
+++ b/tools/broccoli/html-replace/SCRIPTS.html
@@ -18,6 +18,7 @@
 <script src="/bundle/http.js"></script>
 <script src="/bundle/router.dev.js"></script>
 <script>
+  window.angularDevMode = true;
   var filename = '@@PATH/@@FILENAME';
   System.import(filename).then(function(m) { m.main(); }, console.error.bind(console));
 </script>
diff --git a/tools/broccoli/js-replace/SCRIPTS.js b/tools/broccoli/js-replace/SCRIPTS.js
index 7ef18d10ad..feb581a9e7 100644
--- a/tools/broccoli/js-replace/SCRIPTS.js
+++ b/tools/broccoli/js-replace/SCRIPTS.js
@@ -1,2 +1,3 @@
+self.angularDevMode = true;
 importScripts("es6-shim.js", "zone-microtask.js", "long-stack-trace-zone.js", "system.src.js",
               "Reflect.js");
diff --git a/tools/cjs-jasmine/index.js b/tools/cjs-jasmine/index.js
index 0e97d7fa61..10fc759c0c 100644
--- a/tools/cjs-jasmine/index.js
+++ b/tools/cjs-jasmine/index.js
@@ -6,6 +6,8 @@ var path = require('path');
 require('es6-shim/es6-shim.js');
 require('reflect-metadata/Reflect');
 
+global.angularDevMode = true;
+
 var jrunner = new JasmineRunner();
 
 // Tun on full stack traces in errors to help debugging