Add PowerOfTwoOrNotTest (#4279)

Author: vil02

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

@@ -4,14 +4,8 @@
  * A utility to check if a given number is power of two or not. For example 8,16
  * etc.
  */
-public class PowerOfTwoOrNot {
-
-    public static void main(String[] args) {
-        assert !checkIfPowerOfTwoOrNot(0);
-        assert checkIfPowerOfTwoOrNot(1);
-        assert checkIfPowerOfTwoOrNot(8);
-        assert checkIfPowerOfTwoOrNot(16);
-        assert checkIfPowerOfTwoOrNot(1024);
+public final class PowerOfTwoOrNot {
+    private PowerOfTwoOrNot() {
     }
 
     /**
@@ -21,7 +15,7 @@ public static void main(String[] args) {
      * @return {@code true} if given number is power of two, otherwise
      * {@code false}
      */
-    public static boolean checkIfPowerOfTwoOrNot(int number) {
+    public static boolean checkIfPowerOfTwoOrNot(final int number) {
         return number != 0 && ((number & (number - 1)) == 0);
     }
 }

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

@@ -0,0 +1,25 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+public class PowerOfTwoOrNotTest {
+    @Test
+    public void testPowerOfTwoOrNotForPowersOfTwo() {
+        final var powersOfTwo = new int[] {1, 2, 4, 8, 16, 32, 64};
+        for (final var n : powersOfTwo) {
+            assertTrue(PowerOfTwoOrNot.checkIfPowerOfTwoOrNot(n));
+        }
+    }
+
+    @Test
+    public void testPowerOfTwoOrNotForNotPowersOfTwo() {
+        final var notPowersOfTwo = new int[] {-16, -8, -6, -5, -4, -3, -2, -1, 0, 3, 5, 6, 7, 9, 10, 11, 33, 63, 65, 1000, 9999};
+        for (final var n : notPowersOfTwo) {
+            assertFalse(PowerOfTwoOrNot.checkIfPowerOfTwoOrNot(n));
+        }
+    }
+}