How to mock/unit test a Sling filter that does a redirect? (and other questions)

Question

2 questionsHow I check if the redirect happens in my unit test?I cannot get a proper mock of an OSGI service that provides me access to an OSGI config. When I try to debug my unit test and the execution enters the filter, provider is null. How can I code it so it's not null?some code (unit test + filter class + service)my unit test@ExtendWith(AemContextExtension.class)
class MaintenancePagePrincipalsFilterTest {
    private static final String MAINTENANCE_MODE_FLAG_TRUE = "true";
    private static final String MAINTENANCE_PATH_PATH = "/content/myapp/sg/en/maintenance.html";

@Mock
    private HttpServletRequest request;
    @Mock
    private HttpServletResponse response;
    @Mock
    private FilterChain chain;

private MaintenanceModeConfigurationProvider provider;
    private final AemContext context = new AemContext();
    private MaintenancePageFilter filter;

@BeforeEach
    void setUp() {
        MockitoAnnotations.openMocks(this);

provider = mock(MaintenanceModeConfigurationProvider.class);
        context.registerService(MaintenanceModeConfigurationProvider.class, provider);

filter = new MaintenancePageFilter();
    }

@2785667
    void MaintenanceModeEnabled() throws IOException, ServletException {     when(provider.getMaintenanceModeFlag()).thenReturn(MAINTENANCE_MODE_FLAG_TRUE);        when(provider.getMaintenancePagePath()).thenReturn(MAINTENANCE_PATH_PATH);
        filter.doFilter(request, response, chain);
        verify(response).sendRedirect(MAINTENANCE_PATH_PATH);
        verify(chain, never()).doFilter(request, response);
    }
}filter classpublic class MaintenancePageFilter implements Filter {
    @3214626
    private MaintenanceModeConfigurationProvider provider;

@9944223
    public void init(FilterConfig filterConfig) throws ServletException { }
    @9944223
    public void destroy() { }
    @9944223
    public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
            throws IOException, ServletException {
        try {
            if (StringUtils.isNotBlank(provider.getMaintenanceModeFlag())
                    && StringUtils.isNotBlank(provider.getMaintenancePagePath()) {
                ((HttpServletResponse) response).sendRedirect(
                        provider.getMaintenancePagePath());
                return;
            }
        } catch (IOException exception) {
        } catch (IllegalStateException exception) {
        }
        chain.doFilter(request, response);
    }
}service class to access OSGI configpublic class MaintenanceModeConfigurationProviderImpl implements MaintenanceModeConfigurationProvider {
    private MaintenanceModeConfiguration config;

@580286
    @9182423
    protected void activate(MaintenanceModeConfiguration config) { this.config = config; }

@9944223
    public String getMaintenanceModeFlag() { return config.maintenanceModeFlag(); }

@9944223
    public String getMaintenancePagePath() { return config.maintenancePagePath(); }
}

HrishikeshKagne · Accepted Answer

Hi @jayv25585659 ,Try this:1. How to check redirect in your unit testYou already do the right thing:verify(response).sendRedirect(MAINTENANCE_PATH_PATH);verify(chain, never()).doFilter(request, response);That is exactly how you confirm the redirect happens.2. Why provider is null in your filterYour filter is written as an OSGi DS component but in the test you create it with new, so OSGi never injects @Reference -> provider stays null.Make your filter an OSGi component (@Component(service = Filter.class) + @Reference MaintenanceModeConfigurationProvider provider).In the test, don’t use new. Instead, register the mock in AemContext and let DS injection work:@BeforeEachvoid setUp(AemContext context) {provider = mock(MaintenanceModeConfigurationProvider.class);context.registerService(MaintenanceModeConfigurationProvider.class, provider);// let AemContext create the filter with DS injectionfilter = context.registerInjectActivateService(new MaintenancePageFilter());}Now provider will not be null.Keep verifying sendRedirect to test the redirect.Don’t new your filter; use context.registerInjectActivateService so OSGi injection works and your provider is not null.

AbhishekDa3 · Answer

Hi @jayv25585659

Looking at your test class, the reason that provider object is null because the MaintenancePageFilter instance is not getting the mocked MaintenanceModeConfigurationProvider injected into it.

The issue is in your setup:

You're registering the mock provider with the AemContext
But you're creating the filter with new MaintenancePageFilter() instead of letting AemContext create and inject dependencies

As @hrishikeshkagne mentioned, registerInjectActivateService method ensures the mocked provider gets properly injected into the filter instance.

filter = context.registerInjectActivateService(new MaintenancePageFilter());

Based on my previous experience, this may not work, since AemContext can't handle the dependency injection automatically. You may need to manually inject the provider using reflection. So, instead of using,

filter = context.registerInjectActivateService(new MaintenancePageFilter());

try the below code snippet.

filter = new MaintenancePageFilter();       
// Manually inject the provider using reflection
Field providerField = MaintenancePageFilter.class.getDeclaredField("provider");
providerField.setAccessible(true);
providerField.set(filter, provider);

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