From e41c2b9456f1bb25756095a58e8096994dbee10b Mon Sep 17 00:00:00 2001
From: Saipriya Patnaik <143923417+Saipatnaik-23@users.noreply.github.com>
Date: Wed, 11 Jun 2025 02:37:24 +0530
Subject: [PATCH] Add Unit Tests for Empty and Single-Node Graphs in
 TopologicalSort (#6263)

---
 .../thealgorithms/sorts/TopologicalSortTest.java  | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/test/java/com/thealgorithms/sorts/TopologicalSortTest.java b/src/test/java/com/thealgorithms/sorts/TopologicalSortTest.java
index de115b458..d5588b2b9 100644
--- a/src/test/java/com/thealgorithms/sorts/TopologicalSortTest.java
+++ b/src/test/java/com/thealgorithms/sorts/TopologicalSortTest.java
@@ -3,6 +3,7 @@ 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 static org.junit.jupiter.api.Assertions.assertTrue;
 
 import com.thealgorithms.sorts.TopologicalSort.Graph;
 import java.util.LinkedList;
@@ -59,4 +60,18 @@ class TopologicalSortTest {
             + "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());
+    }
 }