Unstable runs of Test Cases

Anil is for sure pointing you in the correct direction here.
Its called ‘Data Driven Testing’. You can put the 20 urls into an Excel file, and then import that into the test case. It then converts it to a JSON which gets stored in the project.

When you run the test case you can then choose which of the 20 ‘variations’ you want to run and can run them all at once if you choose.

These will allow you to evaluate which URLs pass and which URLs fail.

So its still only one test case, since you are apparently testing the same thing, but you can use as many different URLs as you like