@Override
  public Stream<CoreExtension> loadedCoreExtensions() {
    checkInitialized();

    return coreExtensions.stream();
  }
@Test
  public void loadedCoreExtensions_fails_with_ISE_if_called_before_setLoadedCoreExtensions() {
    assertThatThrownBy(() -> underTest.loadedCoreExtensions())
      .isInstanceOf(IllegalStateException.class)
      .hasMessage("Repository has not been initialized yet");
  }