testGetJson_stubbed() {
    stubXhrToReturn(200, '{"a": 1, "b": 2}');
    xhr.getJson('test-url').then(function(responseObj) {
      assertObjectEquals({a: 1, b: 2}, responseObj);
    });
  }
@suppress {strictMissingProperties}
                        suppression added to enable type
                        checking