test: final fix for FactorialTest logic and formatting

Author: VanshSharma3

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

@@ -3,6 +3,8 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
+import java.math.BigInteger;
+
 import org.junit.jupiter.api.Test;
 
 public class FactorialTest {
@@ -16,9 +18,9 @@ public void testWhenInvalidInoutProvidedShouldThrowException() {
 
     @Test
     public void testCorrectFactorialCalculation() {
-        assertEquals(1, Factorial.factorial(0));
-        assertEquals(1, Factorial.factorial(1));
-        assertEquals(120, Factorial.factorial(5));
-        assertEquals(3628800, Factorial.factorial(10));
+        assertEquals(BigInteger.ONE, Factorial.factorial(0));
+        assertEquals(BigInteger.ONE, Factorial.factorial(1));
+        assertEquals(BigInteger.valueOf(120), Factorial.factorial(5));
+        assertEquals(BigInteger.valueOf(3628800), Factorial.factorial(10));
     }
 }