Added tests in int module library as a part of rust-lang#76268

Author: Ayush Kumar Mishra

library/core/tests/num/i32.rs

@@ -28,3 +28,8 @@ fn test_arith_operation() {
         i32_c + i32_c * 2 / 3 * 2 + (i32_c - 7 % 3)
     );
 }
+
+#[test]
+fn test_sub_operation() {
+    let mut x: i32 = -400; x = 0 - x; assert_eq!(x, 400);
+}

library/core/tests/num/i8.rs

@@ -1 +1,10 @@
 int_module!(i8, i8);
+
+#[test]
+fn test_incr_operation() {
+    let mut x: i8 = -12;
+    let y: i8 = -12;
+    x = x + 1;
+    x = x - 1;
+    assert_eq!(x, y);
+}