I have a working WebGraphQLInterceptor that does some authorization checks based on a combination of authentication and GraphQL query parameters.

I want to write unit tests that test my CustomGraphQlInterceptor in isolation, not as part of the larger servlet we’re building. But I cannot get the code to execute during a test.

Simplified code:

@Component
class CustomGraphQlInterceptor : WebGraphQlInterceptor {
  private val logger = LoggerFactory.getLogger(javaClass)

  // you can ignore IDE errors about being unable to Autowire this bean, it will
  // successfully autowire at runtime.
  @Suppress("SpringJavaInjectionPointsAutowiringInspection")
  @Autowired
  private lateinit var externalAuthorizationService: ExternalAuthorizationService

  override fun intercept(
    request: WebGraphQlRequest,
    chain: WebGraphQlInterceptor.Chain,
  ): Mono<WebGraphQlResponse> {
    logger.info("Validating request: $request")
    logger.info("Context is  ${ReactiveSecurityContextHolder.getContext()}")
    return ReactiveSecurityContextHolder.getContext().flatMap { securityContext ->
      val authentication = securityContext.authentication
      if (authentication is JwtAuthenticationToken) {
       val externalId = authentication.tokenAttributes["externalId"] as? String

      val queryVariable = request.variables["queryVariable"]
      
      val isAuthorized: Boolean = externalAuthorizationService.isAuthorized(externalId, queryVariable)

     if (!isAuthorized) {
       return@flatMap Mono.error(IllegalAccessException("not authorized"))
     }
     return@flatMap chain.next(request)
  }
}

My test is like this:

@Retention(AnnotationRetention.RUNTIME)
@Target(AnnotationTarget.CLASS)
@ExtendWith(SpringExtension::class)
@SpringBootTest(
    classes = [DgsAutoConfiguration::class, TestConfig::class],
    webEnvironment = WebEnvironment.RANDOM_PORT,
    properties = ["spring.main.web-application-type=reactive", "spring.profiles.active=test"],
)
@TestExecutionListeners(
  ReactorContextTestExecutionListener::class,
  mergeMode = TestExecutionListeners.MergeMode.MERGE_WITH_DEFAULTS,
)
class SupplierGraphQlInterceptorTest {
  @Autowired
  private lateinit var customGraphQlInterceptor: CustomGraphQlInterceptor

  @MockkBean
  private lateinit var externalAuthorizationService: ExternalAuthorizationService

  @BeforeEach
  fun setupAuthorized() {
    TestSecurityContextHolder.setAuthentication(
      JwtAuthenticationToken(
        Jwt(
          "token",
          Instant.now(),
          Instant.MAX,
          mapOf(
            "alg" to "none",
          ),
          mapOf(
            "externalId" to "1",
          ),
        ),
      ),
    )
  }

  @Test
  fun testUserIsAuthorized() {
    val request =
      WebGraphQlRequest(
        URI("http://localhost:8080/graphql"), // uri
        HttpHeaders(CollectionUtils.toMultiValueMap(mapOf())), // headers
        null, // cookies
        null, // remote address
        mapOf(), // attributes
        mapOf( // body
          "query" to "{someQuery{id name}}",
          "operationName" to "POST",
          "variables" to mapOf("queryVariable" to "ABC"),
        ),
        "1", // id
        null, // local
      )

    every {
      authorizationService.isAuthorized(1, "ABC")
    } returns true

    val chain = mockk<WebGraphQlInterceptor.Chain>()
    every { chain.next(any()) } returns Mono.just(mockk<WebGraphQlResponse>())

    StepVerifier
      .create(
        supplierGraphQlInterceptor.intercept(request, chain),
      ).expectNextMatches { it is WebGraphQlResponse }
      .verifyComplete()
  }
}

This fails with

java.lang.AssertionError: expectation “expectNextMatches” failed (expected: onNext(); actual: onComplete())

I am new to DGS, Spring, and kotlin so I am sure I am doing at least several things wrong here.