diff --git a/test/api.js b/test/api.js
index dc018f31a9..2bcd2d0ff3 100644
--- a/test/api.js
+++ b/test/api.js
@@ -1,6 +1,7 @@
-var transform = require("../lib/babel/transformation");
-var assert    = require("assert");
-var File      = require("../lib/babel/transformation/file");
+var buildExternalHelpers = require("../lib/babel/build-external-helpers");
+var transform            = require("../lib/babel/transformation");
+var assert               = require("assert");
+var File                 = require("../lib/babel/transformation/file");
 
 suite("api", function () {
   test("{ code: false }", function () {
@@ -19,4 +20,18 @@ suite("api", function () {
       file.addHelper("foob");
     }, /Unknown helper foob/);
   });
+
+  suite("buildExternalHelpers", function () {
+    test("all", function () {
+      var script = buildExternalHelpers();
+      assert.ok(script.indexOf("classCallCheck") >= -1);
+      assert.ok(script.indexOf("inherits") >= 0);
+    });
+
+    test("whitelist", function () {
+      var script = buildExternalHelpers(["inherits"]);
+      assert.ok(script.indexOf("classCallCheck") === -1);
+      assert.ok(script.indexOf("inherits") >= 0);
+    });
+  });
 });