@WithMockUser in a parallel context

The following code is just a simplified version of what I want to achieve.

I am using @WithMockUser(username = "jane@no-domain.com", authorities = {"ROLE_ADMIN"}) to mock a user in my tests.

@RunWith(SpringRunner.class)
@SpringBootTest
@EnableAsync
@WithMockUser(username = "jane@no-domain.com", authorities = {"ROLE_ADMIN"})
public class NonTest {

    @Test
    public void test() {
        IntStream.range(1, 10)
            .parallel() // Comment this and it will work
            .forEach(value -> {
                getUser(value);
            });
    }

    public void getUser(int value) {
        System.out.println(value + ": " + ((User) SecurityContextHolder.getContext().getAuthentication().getPrincipal()).getUsername());
    }

}

When I execute the above code with .parallel() commented out, it works and prints out the following as intended:

1: jane@no-domain.com
2: jane@no-domain.com
3: jane@no-domain.com
4: jane@no-domain.com
5: jane@no-domain.com
6: jane@no-domain.com
7: jane@no-domain.com
8: jane@no-domain.com
9: jane@no-domain.com

... but when I add the .parallel() it throws a NullPointerException since somehow the mocked user is not present.

It behaves the same way when I use an ExecutorService or any threading of some sort.

So, how do I execute the method in parallel?

The use of .parallel() will spawn multiple threads to run over the stream in parallel. From the tutorial on streams:

> When a stream executes in parallel, the Java runtime partitions the
> stream into multiple substreams. Aggregate operations iterate over and
> process these substreams in parallel and then combine the results.

So you need to make the children threads inherit the SecurityContextHolder from the local thread, for this you could use @PostConstruct as follows, (see more info here):

@SpringBootTest
@EnableAsync
@WithMockUser(username = "jane@no-domain.com", authorities = {"ROLE_ADMIN"})
public class NonTest {

    @Test
    public void test() {
        IntStream.range(1, 10)
            .parallel()
            .forEach(this::getUser);
    }

    @PostConstruct
    void setGlobalSecurityContext() {
        SecurityContextHolder.setStrategyName(SecurityContextHolder.MODE_INHERITABLETHREADLOCAL);
    }

    public void getUser(int value) {
        System.out.println(value + ": " + ((User) SecurityContextHolder.getContext().getAuthentication().getPrincipal()).getUsername());
    }

}

Output

6: jane@no-domain.com
7: jane@no-domain.com
1: jane@no-domain.com
2: jane@no-domain.com
3: jane@no-domain.com
9: jane@no-domain.com
4: jane@no-domain.com
8: jane@no-domain.com
5: jane@no-domain.com