Inject @AuthenticationPrincipal when unit testing a Spring REST controller

Question

I am having trouble trying to test a REST endpoint that receives an UserDetails as a parameter annotated with @AuthenticationPrincipal.

It

Answer 1

I know the question is old but for folks still looking, what worked for me to write a Spring Boot test with @AuthenticationPrincipal (and this may not work with all instances), was annotating the test @WithMockUser("testuser1")

@Test
@WithMockUser("testuser1")
public void successfullyMockUser throws Exception {
    mvc.perform(...));
}

Here is a link to the Spring documentation on @WithMockUser