code: public static void reset() {
      ShadowApplication shadowApplication = Shadow.extract(RuntimeEnvironment.application);
      shadowApplication.getShownToasts().clear();
    }
docs: Discards the recorded {@code Toast}s. Shown toasts are automatically cleared between
  tests. This method allows the user to discard recorded toasts during the test in order to make assertions clearer
  e.g:
  
  <pre>
  
  // Show a single toast
  myClass.showToast();
  
  assertThat(ShadowToast.shownToastCount()).isEqualTo(1);
  ShadowToast.reset();
  
  // Show another toast
  myClass.showToast();
  
  assertThat(ShadowToast.shownToastCount()).isEqualTo(1);
  
  </pre>