Add new file

MultiplierTest.java

+import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+
+public class MultiplierTest {
+
+    @Test
+    public void testMultiply() {
+        // Test case 1
+        assertEquals(6, Multiplier.multiply(2, 3));
+
+        // Test case 2
+        assertEquals(20, Multiplier.multiply(4, 5));
+
+        // Test case 3
+        assertEquals(0, Multiplier.multiply(0, 10));
+
+        // Test case 4
+        assertEquals(0, Multiplier.multiply(7, 0));
+
+        // Test case 5
+        assertEquals(15, Multiplier.multiply(1, 15));
+    }
+}