Mocked MessageSource executes real method

[andreasarf]

Problems:

When mocking org.springframework.context.MessageSource, it will execute real method instead of mocked behavior.

org.springframework.context.NoSuchMessageException: No message found under code 'billing.cycle.created' for locale 'en_ID'.

	at org.springframework.context.support.DelegatingMessageSource.getMessage(DelegatingMessageSource.java:76)

Steps to reproduce:

1. Have a service class that include MessageSource as a bean.
2. Create a test class for that service class.
   • Use SpringExtension
   • Mock all dependencies using MockBean
   • Mock the behavior of the method getMessage using Mockito.when
3. Run the test.

Actual: throw exception and it seems to call real method.
Expected: no exception and returns the output specified via Mockito

Can use this code as a reference: https://github.com/andreasarf/simple-billing-engine/pull/1/files

NOTE: I have tried using the latest version of Spring Boot which uses MockitoBean and the faulty behavior is still there.

Details:

• Spring Boot 3.3.4
• Java 21

[wilkinsona]

This behavior is to be expected given your test's configuration.

There's no existing MessageSource bean in the context so, as described in its javadoc, @MockBean generates a name. This generated name does not match org.springframework.context.support.AbstractApplicationContext#MESSAGE_SOURCE_BEAN_NAME so the context does not use the mocked message source.

To fix the problem, you should specify the name when mocking the bean:

@MockBean(name = AbstractApplicationContext.MESSAGE_SOURCE_BEAN_NAME)