Update tests

src/assignments/assignment01_grade.rs

@@ -3,22 +3,22 @@ mod test {
     use super::super::assignment01::*;
 
     #[test]
-    fn add_7_3() {
+    fn test_add_7_3() {
         assert_eq!(add(7, 3), 10);
     }
 
     #[test]
-    fn add_overflow() {
+    fn test_add_overflow() {
         assert_eq!(add(usize::MAX, 1), usize::MIN);
     }
 
     #[test]
-    fn sub_7_3() {
+    fn test_sub_7_3() {
         assert_eq!(sub(7, 3), 4);
     }
 
     #[test]
-    fn sub_overflow() {
+    fn test_sub_overflow() {
         assert_eq!(sub(usize::MIN, 1), usize::MAX);
     }
 }