feat(hint): Add test for hint

tests/fixture/failure/info.toml

@@ -2,10 +2,10 @@
 name = "compFailure"
 path = "compFailure.rs"
 mode = "compile"
-hint = """"""
+hint = ""
 
 [[exercises]]
 name = "testFailure"
 path = "testFailure.rs"
 mode = "test"
-hint = """"""
+hint = "Hello!"