Add Kaprekar Numbers (#2881)

src/test/java/com/thealgorithms/maths/KaprekarNumbersTest.java

@@ -0,0 +1,58 @@
+package com.thealgorithms.maths;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class KaprekarNumbersTest {
+
+	@Test
+	void testFor1() 
+	{
+		assertTrue(KaprekarNumbers.isKaprekarNumber(1));
+	}
+
+	@Test
+	void testFor45() 
+	{
+		assertTrue(KaprekarNumbers.isKaprekarNumber(45));
+	}
+
+	@Test
+	void testFor297() 
+	{
+		assertTrue(KaprekarNumbers.isKaprekarNumber(297));
+	}
+
+	@Test
+	void testFor2223() 
+	{
+		assertTrue(KaprekarNumbers.isKaprekarNumber(2223));
+	}
+
+	@Test
+	void testFor857143() 
+	{
+		assertTrue(KaprekarNumbers.isKaprekarNumber(857143));
+	}
+
+
+	@Test
+	void testFor3() 
+	{
+		assertFalse(KaprekarNumbers.isKaprekarNumber(3));
+	}
+
+	@Test
+	void testFor26() 
+	{
+		assertFalse(KaprekarNumbers.isKaprekarNumber(26));
+	}
+
+	@Test
+	void testFor98() 
+	{
+		assertFalse(KaprekarNumbers.isKaprekarNumber(98));
+	}
+
+}