Sometimes you may want to check that a file exists, but not care about (or know) the contents of it. In the latter case you could use a code pattern, and in this guide we'll accomplish the former with a custom test.
Here's the custom test creation form filled out with the required values:
You can read about most of these values here — the only important one for this guide are the Test Contents, shown below:
True if a file exists, otherwise
assertwill trigger an
AssertionError if passed a falsey value which will be caught by the Failed Pattern, and the test will fail.
To wrap up, save your check, and add it to a task.