Add Tests for DigitalRoot Algorithm (#3186)

src/main/java/com/thealgorithms/maths/DigitalRoot.java

@@ -60,12 +60,6 @@ class DigitalRoot {
     }                                                             // n / 10 is the number obtainded after removing the digit one by one  
     // Sum of digits is stored in the Stack memory and then finally returned
 
-    public static void main(String[] args) {
-        Scanner sc = new Scanner(System.in);
-        System.out.println("Enter the number : ");
-        int n = sc.nextInt();                                     // Taking a number as input from the user
-        System.out.println("Digital Root : " + digitalRoot(n));     // Printing the value returned by digitalRoot() method
-    }
 }
 
 /**

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

@@ -0,0 +1,20 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class DigitalRootTest {
+
+    @Test
+    void testDigitalroot() {
+
+        assertEquals(4, DigitalRoot.digitalRoot(4));
+        assertEquals(9, DigitalRoot.digitalRoot(9));
+        assertEquals(4, DigitalRoot.digitalRoot(49));
+        assertEquals(6, DigitalRoot.digitalRoot(78));
+        assertEquals(4, DigitalRoot.digitalRoot(1228));
+        assertEquals(5, DigitalRoot.digitalRoot(71348));
+        
+    }
+}