Enhance docs, add tests in HeapElement (#5981)

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

@@ -0,0 +1,55 @@
+package com.thealgorithms.datastructures.heaps;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+class HeapElementTest {
+
+    @Test
+    void testConstructorAndGetters() {
+        HeapElement element = new HeapElement(5.0, "Info");
+        assertEquals(5.0, element.getKey());
+        assertEquals("Info", element.getInfo());
+    }
+
+    @Test
+    void testConstructorWithNullInfo() {
+        HeapElement element = new HeapElement(10);
+        assertEquals(10, element.getKey());
+        assertNull(element.getInfo());
+    }
+
+    @Test
+    void testToString() {
+        HeapElement element = new HeapElement(7.5, "TestInfo");
+        assertEquals("Key: 7.5 - TestInfo", element.toString());
+
+        HeapElement elementWithoutInfo = new HeapElement(3);
+        assertEquals("Key: 3.0 - No additional info", elementWithoutInfo.toString());
+    }
+
+    @Test
+    void testEquals() {
+        HeapElement element1 = new HeapElement(2.5, "Data");
+        HeapElement element2 = new HeapElement(2.5, "Data");
+        HeapElement element3 = new HeapElement(3.0, "DifferentData");
+
+        assertEquals(element1, element2); // Same key and info
+        assertNotEquals(element1, element3); // Different key
+        assertNotEquals(null, element1); // Check for null
+        assertNotEquals("String", element1); // Check for different type
+    }
+
+    @Test
+    void testHashCode() {
+        HeapElement element1 = new HeapElement(4, "HashMe");
+        HeapElement element2 = new HeapElement(4, "HashMe");
+        HeapElement element3 = new HeapElement(4, "DifferentHash");
+
+        assertEquals(element1.hashCode(), element2.hashCode()); // Same key and info
+        assertNotEquals(element1.hashCode(), element3.hashCode()); // Different info
+    }
+}