### Question:
AbstractProviderHandlerRegistry { public boolean isProviderInstalled(ProviderTypeKey providerTypeKey) { return getProviderHandler(providerTypeKey) != null; } protected  AbstractProviderHandlerRegistry(); protected  AbstractProviderHandlerRegistry(final Instance<T> handlerInstance); boolean isProviderInstalled(ProviderTypeKey providerTypeKey); T getProviderHandler(ProviderTypeKey providerTypeKey);  }### Answer:
@Test public void testProvidersInstalled() { expectedKeys.forEach(key -> assertTrue(handlerRegistry.isProviderInstalled(key))); }
@Test public void testProviderNotInstalled() { ProviderTypeKey providerTypeKey = mock(ProviderTypeKey.class); assertFalse(handlerRegistry.isProviderInstalled(providerTypeKey)); }