feat(tests): add hint comments

exercises/tests/tests1.rs

@@ -4,7 +4,8 @@
 // rustlings run tests1
 
 // This test has a problem with it -- make the test compile! Make the test
-// pass! Make the test fail! Execute `rustlings hint tests1` for hints :)
+// pass! Make the test fail!
+// Execute `rustlings hint tests1` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
 

exercises/tests/tests2.rs

@@ -1,6 +1,7 @@
 // tests2.rs
 // This test has a problem with it -- make the test compile! Make the test
-// pass! Make the test fail! Execute `rustlings hint tests2` for hints :)
+// pass! Make the test fail!
+// Execute `rustlings hint tests2` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE
 

exercises/tests/tests3.rs

@@ -2,7 +2,7 @@
 // This test isn't testing our function -- make it do that in such a way that
 // the test passes. Then write a second test that tests whether we get the result
 // we expect to get when we call `is_even(5)`.
-// Execute `rustlings hint tests3` for hints :)
+// Execute `rustlings hint tests3` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE