feat: completed tests

exercises/17_tests/tests1.rs

@@ -13,11 +13,12 @@ fn main() {
 mod tests {
     // TODO: Import `is_even`. You can use a wildcard to import everything in
     // the outer module.
+    use super::*;
 
     #[test]
     fn you_can_assert() {
         // TODO: Test the function `is_even` with some values.
-        assert!();
-        assert!();
+        assert!(!is_even(1));
+        assert!(is_even(12));
     }
 }