@Test
public void should_classify_instance_without_classifier() {

	// Given
	String regressorName = "TestLearner";
	RegressionQuery query = new RegressionQuery(regressorName);
	TridentTuple tuple1 = mock(TridentTuple.class);
	TridentTuple tuple2 = mock(TridentTuple.class);
	List<TridentTuple> tuples = Arrays.asList(tuple1, tuple2);
	List<List<Object>> expectedKeys = asList(asList((Object) regressorName));
	MapState<Regressor> state = mock(MapState.class);
	given(state.multiGet(expectedKeys)).willReturn(EMPTY_LIST);
	// When
	List<Double> actualPredictions = query.batchRetrieve(state, tuples);
	assertEquals(2, actualPredictions.size());
	assertNull(actualPredictions.get(0));
	assertNull(actualPredictions.get(1));
}