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Merged
merged 2 commits into from
Jul 24, 2025
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testing: improve test coverage DequeTest #6429

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96dd008
testing: improve test coverage DequeTest
alxkm Jul 21, 2025
9933877
Merge branch 'master' into testing/DequeTests
DenizAltunkapan Jul 24, 2025
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73 changes: 73 additions & 0 deletions src/test/java/com/thealgorithms/datastructures/queues/DequeTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -121,4 +121,77 @@ void testNullValues() {
assertNull(deque.pollFirst());
org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty());
}

@Test
void testMultipleAddFirst() {
Deque<Integer> deque = new Deque<>();
deque.addFirst(1);
deque.addFirst(2);
deque.addFirst(3);

assertEquals(3, deque.peekFirst(), "First element should be the last added to front");
assertEquals(1, deque.peekLast(), "Last element should be the first added to front");
assertEquals(3, deque.size(), "Size should reflect all additions");
}

@Test
void testMultipleAddLast() {
Deque<Integer> deque = new Deque<>();
deque.addLast(1);
deque.addLast(2);
deque.addLast(3);

assertEquals(1, deque.peekFirst(), "First element should be the first added to back");
assertEquals(3, deque.peekLast(), "Last element should be the last added to back");
assertEquals(3, deque.size(), "Size should reflect all additions");
}

@Test
void testSingleElementOperations() {
Deque<Integer> deque = new Deque<>();
deque.addFirst(1);

assertEquals(1, deque.peekFirst(), "Single element should be both first and last");
assertEquals(1, deque.peekLast(), "Single element should be both first and last");
assertEquals(1, deque.size());

assertEquals(1, deque.pollFirst(), "Should be able to poll single element from front");
org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty(), "Deque should be empty after polling single element");
}

@Test
void testSingleElementPollLast() {
Deque<Integer> deque = new Deque<>();
deque.addLast(1);

assertEquals(1, deque.pollLast(), "Should be able to poll single element from back");
org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty(), "Deque should be empty after polling single element");
}

@Test
void testMixedNullAndValues() {
Deque<String> deque = new Deque<>();
deque.addFirst("first");
deque.addLast(null);
deque.addFirst(null);
deque.addLast("last");

assertEquals(4, deque.size(), "Should handle mixed null and non-null values");
assertNull(deque.pollFirst(), "Should poll null from front");
assertEquals("first", deque.pollFirst(), "Should poll non-null value");
assertNull(deque.pollLast().equals("last") ? null : deque.peekLast(), "Should handle null correctly");
}

@Test
void testSymmetricOperations() {
Deque<Integer> deque = new Deque<>();

// Test that addFirst/pollFirst and addLast/pollLast are symmetric
deque.addFirst(1);
deque.addLast(2);

assertEquals(1, deque.pollFirst(), "addFirst/pollFirst should be symmetric");
assertEquals(2, deque.pollLast(), "addLast/pollLast should be symmetric");
org.junit.jupiter.api.Assertions.assertTrue(deque.isEmpty(), "Deque should be empty after symmetric operations");
}
}