assertTrue(item1.equals(item1));

        // Same input value (id doesn't matter)
        assertTrue(item1.equals(item2));
        assertTrue(item1.equals(item3));

        // Different input value
        assertFalse(item1.equals(item4));

        // Null and different class
        assertFalse(item1.equals(null));
        assertFalse(item1.equals("string"));
        assertFalse(item1.equals(new Object()));
    }

        ProtwordsItem item4 = new ProtwordsItem(1, "word");

        // Same object
        assertTrue(item1.equals(item1));

        // Same input, different id
        assertTrue(item1.equals(item2));

        // Different input
        assertFalse(item1.equals(item3));

        // Same id and input
        assertTrue(item1.equals(item4));

    }

    /**
     * Merges two suggest items.
     * @param item1 The first suggest item.
     * @param item2 The second suggest item.
     * @return The merged suggest item.
     */
    public static SuggestItem merge(final SuggestItem item1, final SuggestItem item2) {
        if (!item1.getId().equals(item2.getId())) {
            throw new IllegalArgumentException("Item id is mismatch.");
        }

        CharMappingItem item4 = new CharMappingItem(4L, inputs1, "different");

        // Test reflexivity
        assertTrue(item1.equals(item1));

        // Test symmetry and arrays with different order
        assertTrue(item1.equals(item2));
        assertTrue(item2.equals(item1));

        // Test with different inputs
        assertFalse(item1.equals(item3));

        assertArrayEquals(languages, item.getLanguages());
        assertEquals(1, item.getKinds().length);
        assertEquals(SuggestItem.Kind.QUERY, item.getKinds()[0]);
        assertEquals(50L, item.getQueryFreq());
        assertEquals(100L, item.getDocFreq());
        assertEquals(1.5f, item.getUserBoost(), 0.001f);
        assertNotNull(item.getTimestamp());
        assertNotNull(item.getId());
    }

    @Test

        final Set<String> mergedIdSet = new HashSet<>();
        final List<SuggestItem> mergedList = new ArrayList<>(items.length);

        for (final SuggestItem item1 : items) {
            final String item1Id = item1.getId();
            if (mergedIdSet.contains(item1Id)) {
                continue;
            }

            SuggestItem mergedItem = item1;

        TestDictionaryItem item1 = new TestDictionaryItem();
        TestDictionaryItem item2 = new TestDictionaryItem();

        item1.id = 100L;
        item2.id = 200L;

        assertEquals(100L, item1.getId());
        assertEquals(200L, item2.getId());

        // Verify they don't affect each other
        item1.id = 300L;
        assertEquals(300L, item1.getId());
        assertEquals(200L, item2.getId());

        assertEquals(2, result.size());

        CharMappingItem item1 = result.get(0);
        assertArrayEquals(new String[] { "α", "β" }, item1.getInputs());
        assertEquals("γ", item1.getOutput());

        CharMappingItem item2 = result.get(1);
        assertArrayEquals(new String[] { "中", "文" }, item2.getInputs());
        assertEquals("字", item2.getOutput());
    }

    // Test with very long input line

        assertTrue(result.isPresent());
        assertEquals(testValue, result.get());
    }

    public void test_ofNullable_withList() {
        List<String> testValue = Arrays.asList("item1", "item2", "item3");
        OptionalEntity<List<String>> result = OptionalUtil.ofNullable(testValue);

        assertNotNull(result);
        assertTrue(result.isPresent());
        assertEquals(testValue, result.get());

        // Test getting non-existing item
        OptionalEntity<ProtwordsItem> item = protwordsFile.get(999);
        assertFalse(item.isPresent());
    }

    public void test_get_withUnloadedData() {
        // Test getting item when data is not loaded yet
        OptionalEntity<ProtwordsItem> item = protwordsFile.get(1);
        assertTrue(item.isPresent());
        assertEquals("test1", item.get().getInput());
    }