Removed graphsearch folder and added additional unit tests for TopologicalSort

Author: Saipatnaik-23

src/test/java/com/thealgorithms/sorts/TopologicalSortTest.java

@@ -1,13 +1,11 @@
 package com.thealgorithms.sorts;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertIterableEquals;
-import static org.junit.jupiter.api.Assertions.assertThrows;
-
 import com.thealgorithms.sorts.TopologicalSort.Graph;
 import java.util.LinkedList;
 import org.junit.jupiter.api.Test;
 
+import static org.junit.jupiter.api.Assertions.*;
+
 class TopologicalSortTest {
 
     @Test
@@ -59,4 +57,18 @@ public void failureTest() {
             + "Back edge: 6 -> 2";
         assertEquals(exception.getMessage(), expected);
     }
+    @Test
+    void testEmptyGraph() {
+        Graph graph = new Graph();
+        LinkedList<String> sorted = TopologicalSort.sort(graph);
+        assertTrue(sorted.isEmpty());
+    }
+    @Test
+    void testSingleNode() {
+        Graph graph = new Graph();
+        graph.addEdge("A", "");
+        LinkedList<String> sorted = TopologicalSort.sort(graph);
+        assertEquals(1, sorted.size());
+        assertEquals("A", sorted.getFirst());
+    }
 }