Java, Spring: Testing DAOs for DataAccessException with Mockito

Question

I'm trying to increase my test coverage so I'm wondering, how would you go about testing for DataAccessExceptions being thrown in a DAO, for example in a simple findAll method which just returns all the data from your data source? In my case, I'm using Spring JdbcTemplates.

For general testing I have my setUp-method with an @Before annotation, mocking the jdbcTemplate used, setting it up in the DAO and mocking all jdbc calls. Now forcing a DataAccessException for something like a create method is pretty simple, just throw the exception when calling a create statement with the right primary keys.

However, I really have no idea how to handle this for methods like simple findAll methods which don't take any input parameters. Testing the valid implementation is straight forward, but how would you go about mocking having no DB connection without it affecting every other test or method?

This would be a concrete implementation of a method I'd like to test:

  public List<SomeObject> findAll() throws PersistenceException {
    final String sql = "SELECT * FROM SomeObject";

    try {
      return jdbcTemplate.query(sql, new JdbcSomeObjectMapper());
    } catch (DataAccessException ex) {
      LOG.error(ex.getMessage());
      throw new PersistenceException(ex.getMessage());
    }
  }

Which would just return all objects in the data source. Testing for a valid call is easy since I can just mock the jdbcTemplate.query call, but I'd never enter the catch block unless there's a connection failure while retrieving the data, and that's what I'd like to test.

Answer 1

Using Mockito you can mock a Class and the method calls of that particular Class. A mocked object can also be asked to throw an exception when particular methods are called on it. First you have to mock your jdbcTemplate, then stub your exception

   //mocking JdbcTemplate
JdbcTemplate template = Mockito.mock(JdbcTemplate.class);
Mockito.when(template.query(Mockito.anyString(), (RowMapper<YourClass>)  Mockito.any(RowMapper.class))).thenThrow(EmptyResultDataAccessException.class);

    //or using EasyMock
 EasyMock.expect(template.query(Mockito.anyString(), (RowMapper<YourClass>)  Mockito.any(RowMapper.class))).andThrow(new (typeofExecption));