Sunday, March 11, 2018

Testing native @JsType in GWT tests


I've a simple JavaScript:

var ns = {
  Person: function() {
    this.sayHello = function() {
      return 'Hi';

And I used it to test JsInterop annotation `@JsType` in my GWT test. I injected JS code to
GWTTestCase and tried to retrieve the definition via `@JsType`. However, it doesn't
work, it seems that GWT cannot find the method (see Travis CI [1]):

> [INFO] [ERROR] function @io.mincongh.client.interop.GwtTestJsInterop$Person::sayHello() NOT FOUND, thisObj:, methodName: @io.mincongh.client.interop.GwtTestJsInterop$Person::sayHello()
> [INFO] Tests run: 2, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 11.342 sec <<< FAILURE!

Actually, my code is pretty simple:

public class GwtTestJsInterop extends GWTTestCase {
  public void gwtSetUp() {
    String js = "var ns = { Person: function() { this.sayHello = function() { return 'Hi'; }; } }";

  public String getModuleName() {
    return R.JUNIT_MODULE;

  public void testJsni() {
    assertEquals("Hi", sayHello());

  private native String sayHello() /*-{
    var p = new ns.Person();
    return p.sayHello();

  public void testJsType() {
    Person p = new Person();
    String words = p.sayHello();
    assertEquals("Hi", words);

  @JsType(namespace = "ns", isNative = true)
  private static class Person {
    public native String sayHello();

Note: The 2nd test method, `testJsni()`, runs successfully, so the JS should be
injected correctly. I also have the flag `generateJsInteropExports` enabled in the
Maven GWT plugin in the POM [2]. So what am I missing?

I'm using GWT 2.8.2 and Maven GWT plugin 2.8.2. Any help will be appreciated!

Thank you,
Mincong HUANG

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