I'm finding it tough to test my client-side code without testing implementation details.
For example, lets say you are testing a login form that displays client-side validation errors and does not submit unless the email and password are present and correctly formatted.
You could write a test independent of classnames, etc. to check if the form did not submit (e.g. no POST request was sent) but if I want to check for specific errors I need to either a) rely on specific error messages or b) specific class names which are both liable to change.