How can I mock out various result sets in my unit tests when we're using Spring to autowire the DAO?

Let's say I have a manager that looks something like this:

public class CustomerManager {

    @Autowired
    @Qualifier("customerDAO")
    private CustomerDAO customerDAO;

    public List<Customer> findCustomers() {

        List<Customer> customers = customerDAO.findCustomers();
        if (customers.size() == 0) {
            // Do something else...
        }
        if (customers.size() == 1) {
            // Do something else...
        }

        return customers;
    }
}

Now a sample of how my test is configured:

public class CustomerManagerUnitTest extends AbstractDependencyInjectionSpringContextTests {

    protected String[] getConfigLocations() {
        return new String[] { "classpath:test-spring-customer.xml" };
    }

    public void testFindCustomers_NoResults() {

        CustomerManager customerManager = new CustomerManager();
        List<Customer> customers = customerManager.findCustomers();

        // Test...
    }

    public void testFindCustomers_OneRe开发者_如何学Gosult() {

        CustomerManager customerManager = new CustomerManager();
        List<Customer> customers = customerManager.findCustomers();

        // Test...
    }

    public void testFindCustomers_MultipleResults() {

        CustomerManager customerManager = new CustomerManager();
        List<Customer> customers = customerManager.findCustomers();

        // Test...
    }
}

Depending upon the number of customers (or the type of customer data), I need to do something specific. I'm using Spring's AbstractDependencyInjectionSpringContextTests in order to use test contexts. So getting a mock DAO from a test context config, and autowiring it is no problem. However, that means I would need to have a different context config and different mock DAOs for every test that requires testing a different result set. Right now you can see I only have one test config for my mock DAO. What is the best way to handle this?

---

Don't let Spring create your CustomerManager to test. Create it by hand and inject a mock DAO manually. that's the whole point of dependency injection:

public class CustomerManager {

    private CustomerDAO customerDAO;

    @Autowired
    public CustomerManager(@Qualifier("customerDAO") CustomerDAO customerDAO) {
        this.customerDAO = customerDAO;
    }
}

public class CustomerManagerUnitTest {

    public void testFindCustomers_OneResult() {
        CustomerDAO mockCustomerDAO = ...;
        CustomerManager customerManager = new CustomerManager(mockCustomerDAO);

        expect(customerDAO.findCustomers()).andReturn(...);
        // ...
        List<Customer> customers = customerManager.findCustomers();

        // Test...
    }
}

---

Create the CustomerManager objects yourself, supplying the (mock) DAO. You can use a different mock for the DAO for each test (using Mockito):

class CustomerManagerTest {

    public void testWithNoCustomers() {

        List<Customer> emptyCustomerList = ...;
        CustomerDAO mockCustomerDAO = mock(CustomerDAO.class);
        when(mockCustomerDAO.findCustomers()).thenReturn(emptyCustomerList);

        CustomerManager customerManager = new CustomerManager(mockCustomerDAO);

        // Testing expecting result for no customers case...
    }

    public void testWithOneCustomer() {

        List<Customer> customerListWithOne = ...;
        CustomerDAO mockCustomerDAO = mock(CustomerDAO.class);
        when(mockCustomerDAO.findCustomers()).thenReturn(customerListWithOne);

        CustomerManager customerManager = new CustomerManager(mockCustomerDAO);

        // Testing expecting result for one customer case...
    }
}