How to add custom request header to testcafe test suite?

I have a bunch of tests that I am running through testcafe. Now I need to add a custom request header for each test that uniquely identifies the call is originating from the testcafe suite and not a real user. Is there a way to add the custom header to all the test cases at once? I was looking at https://devexpress.github.io/testcafe/documentation/guides/advanced-guides/intercept-http-requests.html#mock-http-requests but it seems like I would need to update each fixture to get this working. So, I wanted to know if there's a way I can set it on a top level file before calling the test suite?

Thanks.