Mocking DataSource for JdbcTemplate with Mockito

Question

I\'m trying to test a class in a Spring project. I would like to make as many changes as possible in the test class vs. the dao class so that I don\'t have to retest all sor

Answer 1

You can't do this because you don't have control over the JdbcTemplate implementation. You should dependency inject the JdbcTemplate and then mock the JdbcTemplate instead.

This difficulty is pointing out a problem with your code. Your code depends on the concrete instance of JdbcTemplate. It would be less coupled if you used Dependency Injection on it instead.

---

Since you don't want to modify your system under test, you can do this:

Change the template field so it's package protected (ie: remove the private keyword). Then, I'd set it to be a mock(JdbcTemplate.class) after you instantiate the class you're testing. Now you'll be able to use when and verify on the JdbcTemplate directly like you wanted originally.

So the class you're testing will look like this:

public class SystemUnderTest {

JdbcTemplate jdbcTemplate;

    public void setJdbcTemplate(DataSource dataSource) {
        this.template = new JdbcTemplate(dataSource);
    }

}

And your test will do this:

@Before
public void setUp() {
    SystemUnderTest sut = new SystemUnderTest();
    sut.jdbcTemplate = mock(JdbcTemplate.class);                
}

// ...

Answer 2

If you're testing a DAO it makes no sense at all to mock the data source. What are you testing? You need to make a DAO that interacts with the database.

Once you have that working, you're free to mock the interface-based DAO when testing services that use it. You've already tested the DAO; there's no reason to redo it when testing the services.

I'd say you're off-track if you're mocking the data source when testing the DAO.