### Question:
ExternalLinkPresenter implements IsWidget { public void onTextChange(final String text) { if (callback == null) { throw new IllegalStateException("Callback is not set."); } callback.callback(text); } @Inject  ExternalLinkPresenter(final ExternalLinkView view); void onEdit(); @Override Widget asWidget(); void setLink(final String text); void addChangeCallback(final Callback<String> callback); void onTextChange(final String text); void onTextChangeDone();  }### Answer:
@Test(expected = IllegalStateException.class) public void editNoCallbackSet() throws Exception { presenter.onTextChange("hello"); }