Enhance docs, add more tests in MRUCache (#5951)

src/test/java/com/thealgorithms/datastructures/caches/MRUCacheTest.java

@@ -11,27 +11,27 @@ public class MRUCacheTest {
 
     @Test
     public void putAndGetIntegerValues() {
-        MRUCache<Integer, Integer> lruCache = new MRUCache<>(SIZE);
+        MRUCache<Integer, Integer> mruCache = new MRUCache<>(SIZE);
 
         for (int i = 0; i < SIZE; i++) {
-            lruCache.put(i, i);
+            mruCache.put(i, i);
         }
 
         for (int i = 0; i < SIZE; i++) {
-            assertEquals(i, lruCache.get(i));
+            assertEquals(i, mruCache.get(i));
         }
     }
 
     @Test
     public void putAndGetStringValues() {
-        MRUCache<String, String> lruCache = new MRUCache<>(SIZE);
+        MRUCache<String, String> mruCache = new MRUCache<>(SIZE);
 
         for (int i = 0; i < SIZE; i++) {
-            lruCache.put("key" + i, "value" + i);
+            mruCache.put("key" + i, "value" + i);
         }
 
         for (int i = 0; i < SIZE; i++) {
-            assertEquals("value" + i, lruCache.get("key" + i));
+            assertEquals("value" + i, mruCache.get("key" + i));
         }
     }
 
@@ -53,6 +53,73 @@ public class MRUCacheTest {
             mruCache.put(i, i);
         }
 
-        assertEquals(9, mruCache.get(9));
+        // After inserting 10 items, the cache should have evicted the least recently used ones.
+        assertEquals(9, mruCache.get(9)); // Most recently used
+        assertEquals(0, mruCache.get(0)); // Least recently used, should be evicted
+    }
+
+    @Test
+    public void overwriteExistingKey() {
+        MRUCache<Integer, String> mruCache = new MRUCache<>(SIZE);
+        mruCache.put(1, "one");
+        mruCache.put(1, "uno"); // Overwriting the value for key 1
+
+        assertEquals("uno", mruCache.get(1));
+        assertNull(mruCache.get(2)); // Ensure other keys are unaffected
+    }
+
+    @Test
+    public void evictionOrder() {
+        MRUCache<Integer, Integer> mruCache = new MRUCache<>(SIZE);
+
+        for (int i = 0; i < SIZE; i++) {
+            mruCache.put(i, i);
+        }
+
+        // Access a key to make it most recently used
+        mruCache.get(2);
+
+        // Add new items to trigger eviction
+        mruCache.put(5, 5);
+        mruCache.put(6, 6);
+
+        // Key 3 should be evicted since 2 is the most recently used
+        assertEquals(3, mruCache.get(3));
+        assertEquals(4, mruCache.get(4)); // Key 4 should still be available
+        assertEquals(6, mruCache.get(6)); // Key 6 should be available
+    }
+
+    @Test
+    public void cacheHandlesLargeValues() {
+        MRUCache<String, String> mruCache = new MRUCache<>(SIZE);
+
+        for (int i = 0; i < SIZE; i++) {
+            mruCache.put("key" + i, "value" + i);
+        }
+
+        // Verify values
+        for (int i = 0; i < SIZE; i++) {
+            assertEquals("value" + i, mruCache.get("key" + i));
+        }
+
+        // Add large value
+        mruCache.put("largeKey", "largeValue");
+
+        // Verify eviction of the least recently used (key 0 should be evicted)
+        assertEquals("value0", mruCache.get("key0"));
+        assertEquals("largeValue", mruCache.get("largeKey"));
+    }
+
+    @Test
+    public void testEmptyCacheBehavior() {
+        MRUCache<Integer, Integer> mruCache = new MRUCache<>(SIZE);
+
+        // Verify that accessing any key returns null
+        assertNull(mruCache.get(1));
+        assertNull(mruCache.get(100));
+
+        // Adding to cache and checking again
+        mruCache.put(1, 10);
+        assertEquals(10, mruCache.get(1));
     }
 }