added required changes

- fixed grammar in hint and added more specific link
- added comments in test functions
- changed introduction paragraph

exercises/tests/tests4.rs

@@ -1,6 +1,5 @@
 // tests4.rs
-// Correct the tests to
-// Do not change Rectangle::new body
+// Make sure that we're testing for the correct conditions!
 // Execute `rustlings hint tests4` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
@@ -11,6 +10,7 @@ struct Rectangle {
 }
 
 impl Rectangle {
+    // Only change the test functions themselves
     pub fn new(width: i32, height: i32) -> Self {
         if width < 0 || height < 0 {
             panic!("Rectangle width and height cannot be negative!")
@@ -25,16 +25,21 @@ mod tests {
 
     #[test]
     fn correct_width_and_height() {
-        let _rect = Rectangle::new(10, 10);
+        // This test should check if the rectangle is the size that we pass into its constructor
+        let rect = Rectangle::new(10, 20);
+        assert_eq!(???, 10); // check width
+        assert_eq!(???, 20); // check height
     }
 
     #[test]
     fn negative_width() {
+        // This test should check if thread panics when we try to create rectangle with negative width
         let _rect = Rectangle::new(-10, 10);
     }
 
     #[test]
     fn negative_height() {
+        // This test should check if thread panics when we try to create rectangle with negative height
         let _rect = Rectangle::new(10, -10);
     }
 }