Add unit tests for RingBuffer functionality

src/test/java/de/extio/game_engine/util/RingBufferTest.java

@@ -0,0 +1,142 @@
+package de.extio.game_engine.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class RingBufferTest {
+
+	private RingBuffer<String> buffer;
+	private static final int CAPACITY = 3;
+
+	@BeforeEach
+	void setUp() {
+		this.buffer = new RingBuffer<>(CAPACITY);
+	}
+
+	@Test
+	void testConstructor() {
+		assertEquals(CAPACITY, this.buffer.capacity());
+		assertEquals(0, this.buffer.size());
+		assertFalse(this.buffer.isFull());
+		assertThrows(IllegalArgumentException.class, () -> new RingBuffer<>(0));
+		assertThrows(IllegalArgumentException.class, () -> new RingBuffer<>(-1));
+	}
+
+	@Test
+	void testOffer() {
+		assertTrue(this.buffer.offer("A"));
+		assertEquals(1, this.buffer.size());
+		assertEquals("A", this.buffer.peek());
+
+		assertTrue(this.buffer.offer("B"));
+		assertTrue(this.buffer.offer("C"));
+		assertEquals(3, this.buffer.size());
+		assertTrue(this.buffer.isFull());
+
+		// Overwrite oldest
+		assertTrue(this.buffer.offer("D"));
+		assertEquals(3, this.buffer.size());
+		assertEquals("B", this.buffer.peek());
+		assertEquals("B", this.buffer.get(0));
+		assertEquals("C", this.buffer.get(1));
+		assertEquals("D", this.buffer.get(2));
+	}
+
+	@Test
+	void testOfferNull() {
+		assertThrows(NullPointerException.class, () -> this.buffer.offer(null));
+	}
+
+	@Test
+	void testPoll() {
+		assertNull(this.buffer.poll());
+
+		this.buffer.offer("A");
+		this.buffer.offer("B");
+
+		assertEquals("A", this.buffer.poll());
+		assertEquals(1, this.buffer.size());
+		assertEquals("B", this.buffer.peek());
+
+		assertEquals("B", this.buffer.poll());
+		assertEquals(0, this.buffer.size());
+		assertNull(this.buffer.poll());
+	}
+
+	@Test
+	void testPeek() {
+		assertNull(this.buffer.peek());
+
+		this.buffer.offer("A");
+		assertEquals("A", this.buffer.peek());
+		assertEquals(1, this.buffer.size());
+
+		this.buffer.offer("B");
+		assertEquals("A", this.buffer.peek());
+		assertEquals(2, this.buffer.size());
+	}
+
+	@Test
+	void testGet() {
+		this.buffer.offer("A");
+		this.buffer.offer("B");
+		this.buffer.offer("C");
+
+		assertEquals("A", this.buffer.get(0));
+		assertEquals("B", this.buffer.get(1));
+		assertEquals("C", this.buffer.get(2));
+
+		assertThrows(IndexOutOfBoundsException.class, () -> this.buffer.get(-1));
+		assertThrows(IndexOutOfBoundsException.class, () -> this.buffer.get(3));
+
+		this.buffer.offer("D"); // Overwrites A
+		assertEquals("B", this.buffer.get(0));
+		assertEquals("C", this.buffer.get(1));
+		assertEquals("D", this.buffer.get(2));
+	}
+
+	@Test
+	void testClear() {
+		this.buffer.offer("A");
+		this.buffer.offer("B");
+		this.buffer.clear();
+
+		assertEquals(0, this.buffer.size());
+		assertNull(this.buffer.peek());
+		assertFalse(this.buffer.isFull());
+	}
+
+	@Test
+	void testIterator() {
+		this.buffer.offer("A");
+		this.buffer.offer("B");
+		this.buffer.offer("C");
+		this.buffer.offer("D"); // B, C, D
+
+		final Iterator<String> it = this.buffer.iterator();
+		assertTrue(it.hasNext());
+		assertEquals("B", it.next());
+		assertTrue(it.hasNext());
+		assertEquals("C", it.next());
+		assertTrue(it.hasNext());
+		assertEquals("D", it.next());
+		assertFalse(it.hasNext());
+		assertThrows(NoSuchElementException.class, it::next);
+	}
+
+	@Test
+	void testIteratorRemoveUnsupported() {
+		this.buffer.offer("A");
+		final Iterator<String> it = this.buffer.iterator();
+		assertThrows(UnsupportedOperationException.class, it::remove);
+	}
+}