If I had to choose my favorite test framework, it would be Selenium for a few good reasons. One pivotal point being that Selenium is supported in numerous OS such as Mac and Windows for instance, and supporting numerous browsers. Perhaps it’s due to my biased nature of working on web development for several months while at school. Although I’m no expert with Selenium, I do find it quite appealing that it has numerous documentation online, and seems to have earned itself a reputation.
Besides Selenium, I would say AutoIt is also a strong freeware that can be useful for testing purposes, aside from its OS limitations (without the usage of WINE). Further research has also led me to feel similarly about Appium (as I feel about Selenium), only that it’s preferred for native mobile applications.
I spent a bit of time to review over Python, unittest with Python, and manual QA testing (on a surface-level).