diff --git a/javascript/externs/lib/bdd.js b/javascript/externs/lib/bdd.js
new file mode 100644
index 00000000000..dca2d9008c6
--- /dev/null
+++ b/javascript/externs/lib/bdd.js
@@ -0,0 +1,96 @@
+/*
+ * Copyright 2018 Semmle
+ *
+ * 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.
+ */
+
+/**
+ * @fileoverview Simple externs definitions for various BDD and TDD APIs.
+ *
+ * The goal is to declare global functions provided by frameworks like Chai,
+ * Mocha and Jasmine. No type information is included at the moment.
+ *
+ * @externs
+ */
+
+/** @param {...*} args */
+function after(args) {}
+
+/** @param {...*} args */
+function afterAll(args) {}
+
+/** @param {...*} args */
+function afterEach(args) {}
+
+/** @param {...*} args */
+function assert(args) {}
+
+/** @param {...*} args */
+function before(args) {}
+
+/** @param {...*} args */
+function beforeAll(args) {}
+
+/** @param {...*} args */
+function beforeEach(args) {}
+
+/** @param {...*} args */
+function context(args) {}
+
+/** @param {...*} args */
+function describe(args) {}
+
+/** @param {...*} args */
+function expect(args) {}
+
+/** @param {...*} args */
+function fdescribe(args) {}
+
+/** @param {...*} args */
+function fit(args) {}
+
+/** @param {...*} args */
+function it(args) {}
+
+/** @param {...*} args */
+function pending(args) {}
+
+/** @param {...*} args */
+function setup(args) {}
+
+/** @param {...*} args */
+function specify(args) {}
+
+/** @param {...*} args */
+function spyOn(args) {}
+
+/** @param {...*} args */
+function suite(args) {}
+
+/** @param {...*} args */
+function suiteSetup(args) {}
+
+/** @param {...*} args */
+function suiteTeardown(args) {}
+
+/** @param {...*} args */
+function teardown(args) {}
+
+/** @param {...*} args */
+function test(args) {}
+
+/** @param {...*} args */
+function xdescribe(args) {}
+
+/** @param {...*} args */
+function xit(args) {}