If you’ve tried unit testing a Spring controller that accepts a Pageable parameter using JUnit 5 and Mockito with MockMvc, you might have encountered this error:

java.lang.IllegalStateException: No primary or single unique constructor found for interface org.springframework.data.domain.Pageable

This happens because, in a standalone MockMvc test (without loading the full Spring context), Spring doesn’t automatically know how to convert query parameters like page, size, and sort into a Pageable object. Without the proper resolver, it tries to instantiate Pageable directly, which fails because it’s an interface.