Implement unit tests for BidirectionalBFS

Added unit tests for BidirectionalBFS to check path existence.

Author: darkatwi

src/main/java/com/thealgorithms/datastructures/graphs/BidirectionalBFSTest.java

@@ -1,14 +1,20 @@
+package com.thealgorithms.graphs;
+
 import java.util.Map;
 import java.util.List;
 import java.util.HashMap;
 import java.util.Arrays;
 
+import org.junit.Test;
+import static org.junit.Assert.*;
+
 /**
- * Simple test for BidirectionalBFS.
+ * Unit tests for BidirectionalBFS.
  */
 public class BidirectionalBFSTest
 {
-    public static void main(String[] args)
+    @Test
+    public void testPathExists()
     {
         Map<Integer, List<Integer>> graph = new HashMap<>();
         graph.put(0, Arrays.asList(1, 2));
@@ -18,12 +24,19 @@ public static void main(String[] args)
         graph.put(4, Arrays.asList(2, 5));
         graph.put(5, Arrays.asList(3, 4));
 
-        // Test 1
-        boolean result1 = BidirectionalBFS.bidirectionalBFS(graph, 0, 5);
-        System.out.println("Path 0->5 exists: " + result1); // true
+        assertTrue(BidirectionalBFS.bidirectionalBFS(graph, 0, 5));
+    }
 
-        // Test 2
-        boolean result2 = BidirectionalBFS.bidirectionalBFS(graph, 0, 6);
-        System.out.println("Path 0->6 exists: " + result2); // false
+    @Test
+    public void testPathDoesNotExist()
+    {
+        Map<Integer, List<Integer>> graph = new HashMap<>();
+        graph.put(0, Arrays.asList(1));
+        graph.put(1, Arrays.asList(0));
+        // node 2 is isolated
+        graph.put(2, Arrays.asList());
+
+        assertFalse(BidirectionalBFS.bidirectionalBFS(graph, 0, 2));
     }
 }
+