WireMock - Asserting exactly one Authorization header

IntegrationTest.java

    @BeforeAll
    public static void beforeAll(@WireMockInstance WireMockServer server1, @WireMockInstance WireMockServer server2) {
        zephyrWiremockServer = server1;
        slackWiremockServer = server2;

        zephyrWiremockServer.addMockServiceRequestListener(new RequestListener() {
            @Override
            public void requestReceived(Request request, Response response) {
                // if we would fail directly here in listener, JUnit error would be really hard to understand (as no response would be generated)
                // therefore saving the value to assert it later in main test flow
                isZephyrAuthSingleValued = request.getHeaders().getHeader("Authorization").isSingleValued();
            }
        });

        slackWiremockServer.addMockServiceRequestListener(new RequestListener() {
            @Override
            public void requestReceived(Request request, Response response) {
                // if we would fail directly here in listener, JUnit error would be really hard to understand (as no response would be generated)
                // therefore saving the value to assert it later in main test flow
                isSlackAuthSingleValued = request.getHeaders().getHeader("Authorization").isSingleValued();
            }
        });
    }

    @AfterEach
    public void afterEach() {
        assertTrue(isZephyrAuthSingleValued,
                "There must be only one 'Authorization' header in all Zephyr requests");
        assertTrue(isSlackAuthSingleValued,
                "There must be only one 'Authorization' header in all Slack requests");

        zephyrWiremockServer.verify(anyRequestedFor(anyUrl())
                .withBasicAuth(new BasicCredentials("zephyrTestUser", "zephyrTestPassword")));

        slackWiremockServer.verify(anyRequestedFor(anyUrl())
                .withHeader("Authorization", equalTo("Bearer testFakeToken")));

    }