ClassCastException on attempt to mock Querydsl SQLQueryFactory

Mocks can not be cast. Instead of RETURN_DEEP_STUBS mock each method on its own and return a mocked instance of the expected class.

If you do not want to suppress the warnings you will get for not defining the generic types, you can use the @Mock annotation instead to create the mocks, like described here.

This example doesn't make much sense for a testcase (as it tests nothing), but its a showcase on how to avoid the exception.

@RunWith(MockitoJUnitRunner.class) public class Test { @Test public void tryMockQueryDsl() { ProjectableSQLQuery projectableQuery = Mockito.mock(ProjectableSQLQuery.class); // not really needed as this is the default behaviour Mockito.when(projectableQuery.fetchFirst()).thenReturn(null); SQLQuery query = Mockito.mock(SQLQuery.class); Mockito.when(query.from(ArgumentMatchers.<Expression<?>>any())).thenReturn(projectableQuery); SQLQueryFactory sql = Mockito.mock(SQLQueryFactory.class); Mockito.when(sql.select(ArgumentMatchers.<Expression<?>>any())).thenReturn(query); Expression expr = Mockito.mock(Expression.class); sql.select(expr).from(expr).fetchFirst(); } }