assertNotNull(provider1);
        assertNotNull(provider2);
        assertNotSame(provider1, provider2);
    }

    // Test with config returning null time adjustment
    @Test
    public void test_nullTimeAdjustment() {
        FessConfig nullAdjustConfig = new FessConfig.SimpleImpl() {
            private static final long serialVersionUID = 1L;

            @Override
            public String getTimeAdjustTimeMillis() {