Environment: Spring 6.2.0-M1, Java 21 Example project: https://github.com/hantsy/spring6-sandbox/tree/master/test-bean

In the following test, 

@SpringJUnitConfig(classes = Config.class)
class CustomerServiceTest {

    @TestBean(/*methodName = ""*/) // use methodName to specify a custom factory method.
    CustomerService customerService;

    // by default method name is {beanName}TestOverride
    static CustomerService customerServiceTestOverride() {
        return new DummyCustomerService();
    }

    @Test
    public void test(ApplicationContext context) {
        assertThat(context.getBean("customerService"))
                .isSameAs(this.customerService)
                .isInstanceOf(DummyCustomerService.class);
    }

    @Test
    public void testCustomerService() {

        // test bean
        var testCustomer = customerService.findByEmail("dummy@example.com");
        assertThat(testCustomer.firstName()).isEqualTo("dummy first");
        assertThat(testCustomer.lastName()).isEqualTo("dummy last");
        assertThat(customerService.findAll().size()).isEqualTo(0);
    }
}

When declaring a @TestBean varible I have to use the bean name declared in Config, not so flexible.

Hope overriding by type is in a higher priority.

Comment From: sbrannen

When declaring a @TestBean varible I have to use the bean name declared in Config, not so flexible.

Have you seen the name attribute in @TestBean that allows you to specify the name of the bean to override?

Comment From: snicoll

Hope overriding by type is in a higher priority.

TestBean really works on a bean identified by name, it doesn't do anything by type. I am a bit confused by the report as the annotation has a name attribute that you can't have overlooked. Are we missing something?

Comment From: hantsy

When declaring a @TestBean varible I have to use the bean name declared in Config, not so flexible.

Have you seen the name attribute in @TestBean that allows you to specify the name of the bean to override?

yes, I have tried it. When set a name to the bean name, I can rename the variable name to others.

But several years ago when switch to Java Config instead of xml config, as a developer, I would like use type matching as first class citizen for the injecting/mocking everywhere.

Comment From: snicoll

yes, I have tried it. When set a name to the bean name, I can rename the variable name to others.

What's up with the issue title then? It really is confusing. And a duplicate of #32761 that I've requalified accordingly.