Add test case to BinaryPow Algorithm (#3177)

Co-authored-by: Yang Libin <contact@yanglibin.info>

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

@@ -0,0 +1,16 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class BinaryPowTest {
+
+    @Test
+    void testBinPow() {
+        assertEquals(4, BinaryPow.binPow(2, 2));
+        assertEquals(256, BinaryPow.binPow(4, 4));
+        assertEquals(729, BinaryPow.binPow(9, 3));
+        assertEquals(262144, BinaryPow.binPow(8, 6));
+    }
+}