finish tests3

Author: cyz-ing

exercises/tests/tests3.rs

@@ -19,11 +19,11 @@ mod tests {
 
     #[test]
     fn is_true_when_even() {
-        assert!();
+        assert!(is_even(2));
     }
 
     #[test]
     fn is_false_when_odd() {
-        assert!();
+        assert!(is_even(4));
     }
 }