TestAuthenticationChain chain = new TestAuthenticationChain();
        chain.loadResult = null;
        User inputUser = createTestUser("inputuser", "Input User");

        User result = chain.load(inputUser);

        assertNull(result);
        assertEquals(1, chain.loadCalls.size());
        assertEquals(inputUser, chain.loadCalls.get(0));
    }

    // Test load with multiple calls