While it is good to have the test tool stop outputs based on tests, it isn't too insightful to users on the full details of these error messages. It would be more useful to have an output location for a test if these errors appear so that end users can troubleshoot instead of the workflow developer having to work through all of the error messaging.
There are workarounds for this that can be used, but they are often extensive and require the addition of significant logic. Adding optional outputs to the test tool would be a simple fix that could save a lot of hours of debugging when end users find an error.