increasing code coverage for JdbcTemplate mocking

Question

I am mocking JdbcTemplate for unit test cases, as don't want to hit actual database integration.

But it is decreasing my code coverage (Red indicates missing coverage).

Below is the snippet used. Same case happens by using user defined mappers.

final List<String> resultList = new ArrayList<String>();
resultList.add("test1");
resultList.add("test2");
final JdbcTemplate template = Mockito.mock(JdbcTemplate.class);
Mockito.when(
    template.query(Mockito.anyString(), Mockito.any(Object[].class),
        Mockito.any(RowMapper.class))).thenReturn(resultList);
sampleDao.setJdbcTemplate(template);

Any ideas for increasing code coverage in dao class. All methods doesn't suit for user defined row mappers in my case.

Answer 1

One way of doing this is as follows:

final List<String> resultList = new ArrayList<String>();
resultList.add("test1");
resultList.add("test2");

final JdbcTemplate template = mock(JdbcTemplate.class);

when(template.query(anyString(), any(Object[].class), any(RowMapper.class)))
    .thenAnswer(new Answer<List<String>>() {
        @Override
        public Object answer(InvocationOnMock invocation) throws Throwable {
            // Fetch the method arguments
            Object[] args = invocation.getArguments();

            // Fetch the row mapper instance from the arguments
            RowMapper<String> rm = (RowMapper<String>) args[2]; 

            // Create a mock result set and setup an expectation on it
            ResultSet rs = mock(ResultSet.class);
            String expected = "value returned by query";
            when(rs.getString(1)).thenReturn(expected);

            // Invoke the row mapper
            String actual = rm.mapRow(rs, 0);

            // Assert the result of the row mapper execution
            assertEquals(expected, actual);

            // Return your created list for the template#query call
            return resultList;
        }
    });

But as you can see, it's a lot of code to test the row mapper :)

Personally, I would prefer going with an integration test OR moving the row mapper to a class of its own and unit testing it separately.