Enhance docs, add tests in MinHeap (#5985)

src/test/java/com/thealgorithms/datastructures/heaps/MinHeapTest.java

@@ -0,0 +1,141 @@
+package com.thealgorithms.datastructures.heaps;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class MinHeapTest {
+
+    private MinHeap heap;
+
+    @BeforeEach
+    void setUp() {
+        // Create a fresh heap for each test
+        List<HeapElement> elements = Arrays.asList(new HeapElement(5.0, "Five"), new HeapElement(2.0, "Two"), new HeapElement(8.0, "Eight"), new HeapElement(1.0, "One"), new HeapElement(9.0, "Nine"));
+        heap = new MinHeap(elements);
+    }
+
+    @Test
+    void testConstructorWithNullList() {
+        assertThrows(IllegalArgumentException.class, () -> new MinHeap(null));
+    }
+
+    @Test
+    void testConstructorWithEmptyList() {
+        MinHeap emptyHeap = new MinHeap(new ArrayList<>());
+        assertTrue(emptyHeap.isEmpty());
+    }
+
+    @Test
+    void testConstructorWithNullElements() {
+        List<HeapElement> elements = Arrays.asList(new HeapElement(1.0, "One"), null, new HeapElement(2.0, "Two"));
+        MinHeap heap = new MinHeap(elements);
+        assertEquals(2, heap.size());
+    }
+
+    @Test
+    void testInsertElement() {
+        heap.insertElement(new HeapElement(0.5, "Half"));
+        assertEquals(0.5, heap.getElement(1).getKey());
+        assertEquals(6, heap.size());
+    }
+
+    @Test
+    void testInsertNullElement() {
+        assertThrows(IllegalArgumentException.class, () -> heap.insertElement(null));
+    }
+
+    @Test
+    void testGetElementAtIndex() {
+        HeapElement element = heap.getElement(1);
+        assertEquals(1.0, element.getKey());
+        assertEquals("One", element.getValue());
+    }
+
+    @Test
+    void testGetElementAtInvalidIndex() {
+        assertThrows(IndexOutOfBoundsException.class, () -> heap.getElement(0));
+        assertThrows(IndexOutOfBoundsException.class, () -> heap.getElement(10));
+    }
+
+    @Test
+    void testDeleteElement() throws EmptyHeapException {
+        heap.deleteElement(1);
+        assertEquals(2.0, heap.getElement(1).getKey());
+        assertEquals(4, heap.size());
+    }
+
+    @Test
+    void testDeleteElementAtInvalidIndex() {
+        assertThrows(IndexOutOfBoundsException.class, () -> heap.deleteElement(0));
+        assertThrows(IndexOutOfBoundsException.class, () -> heap.deleteElement(10));
+    }
+
+    @Test
+    void testDeleteFromEmptyHeap() {
+        MinHeap emptyHeap = new MinHeap(new ArrayList<>());
+        assertThrows(EmptyHeapException.class, () -> emptyHeap.deleteElement(1));
+    }
+
+    @Test
+    void testExtractMin() throws EmptyHeapException {
+        HeapElement min = heap.getElement();
+        assertEquals(1.0, min.getKey());
+        assertEquals("One", min.getValue());
+        assertEquals(4, heap.size());
+
+        min = heap.getElement();
+        assertEquals(2.0, min.getKey());
+        assertEquals(3, heap.size());
+    }
+
+    @Test
+    void testExtractMinFromEmptyHeap() {
+        MinHeap emptyHeap = new MinHeap(new ArrayList<>());
+        assertThrows(EmptyHeapException.class, () -> emptyHeap.getElement());
+    }
+
+    @Test
+    void testHeapOrder() {
+        // Test that parent is always smaller than or equal to children
+        for (int i = 1; i <= heap.size() / 2; i++) {
+            double parentKey = heap.getElement(i).getKey();
+
+            // Check left child
+            if (2 * i <= heap.size()) {
+                assertTrue(parentKey <= heap.getElement(2 * i).getKey());
+            }
+
+            // Check right child
+            if (2 * i + 1 <= heap.size()) {
+                assertTrue(parentKey <= heap.getElement(2 * i + 1).getKey());
+            }
+        }
+    }
+
+    @Test
+    void testSizeAndEmpty() {
+        assertEquals(5, heap.size());
+        assertFalse(heap.isEmpty());
+
+        // Remove all elements
+        while (!heap.isEmpty()) {
+            try {
+                heap.getElement();
+            } catch (EmptyHeapException e) {
+                Assertions.fail("Should not throw EmptyHeapException while heap is not empty");
+            }
+        }
+
+        assertEquals(0, heap.size());
+        assertTrue(heap.isEmpty());
+    }
+}