function assertSignInFailure(expectedError) {
  // Confirm signInFailure callback triggered with expected argument.
  assertEquals(1, signInFailureCallback.getCallCount());
  // Plain assertObjectEquals cannot be used as Internet Explorer adds the
  // stack trace as a property of the object.
  assertObjectEquals(
      expectedError.toPlainObject(),
      signInFailureCallback.getLastCall().getArgument(0).toPlainObject());
  // Sign in success should not be called.
  assertUndefined(signInCallbackUser);
}
Asserts signInFailure callback called with expected error.
@param {?Object|undefined} expectedError The expected error passed to
    signInFailure callback.