diff --git a/src/test/java/org/psjava/algo/graph/LowestCommonAncestorTest.java b/src/test/java/org/psjava/algo/graph/LowestCommonAncestorTest.java
index <HASH>..<HASH> 100644
--- a/src/test/java/org/psjava/algo/graph/LowestCommonAncestorTest.java
+++ b/src/test/java/org/psjava/algo/graph/LowestCommonAncestorTest.java
@@ -20,5 +20,8 @@ public class LowestCommonAncestorTest {
 

 		Assert.assertEquals("2", r.query("3", "4"));

 		Assert.assertEquals("0", r.query("1", "4"));

+		Assert.assertEquals("4", r.query("4", "4"));

+		Assert.assertEquals("0", r.query("4", "0"));

+		Assert.assertEquals("0", r.query("3", "0"));

 	}

 }
improve unit test - LowestCommonAncestorTest