Learning on your own is fun: you have the option to chase a concept until you are satisfied that you fully understand the concept, to the level you need it. But that is also the downside: as a tester, you have few public sites that offer a series of exercises to ensure that you can build that mental list of conditions that you need to ensure are covered in a testing situation.
I am slightly envious of my developer friends: they have established problem sets that they can use to upgrade their skills, and assist in learning the tricks of their particular programming language. The sites are set up to allow both individual learning and competition as an individual, or as a group. This, for many people, is a great incentive to do these exercises on an infrequent basis, or to reinforce a concept that you recently mastered, but aren't likely to use again quickly.
But for me, these resources are hiding - they are included in some classes, yes, but not in this form. And I have heard from developers that they are frustrated doing more than functional tests: they look for something similar to the "katas" they are familiar with for practicing code concepts, and ask about them. And fail to find them
So imagine my delight when I found a 'simple' exercise: go to [shopping site], type in [item], add all items on the first page that have [special tag] to the shopping cart. Thankfully, since this exercise was using a live site, they didn't want you to try and check out! I figuratively pounced on it, and asked for more things like this. And rushed off to make a mind map of what I needed to do.
Anyone who does do testing can see where this is going - what looks to be a simple four-step task can turn into a large project.
My first approach was, of course, an Experiential Testing one. There is no way I would be able to figure out exactly what was required to complete this exercise without taking a look at what was needed to complete the steps. Was there a "Buy now!" button, or did you have to go to the item description? Were the tags scattered. or grouped? And how does one find these tags? So many questions! And the only way to figure them out, plus find out if there are other tasks that need done is to go to the page, and find out.
An online mind map, and a notebook, were also available. I set the map with the task, and started listing what I encountered. Notes handwritten to make sure that what I find isn't forgotten, and so I have a list of tags and routes to items. And, after a few minutes of exploring the task, I was thankful that I had a large virtual sheet - the potential for testing both the correct, easy path and all the other areas grew quickly. As was expected: this is one of the fun parts about testing. Not only do you need to figure out the 'correct' way to do things, but find all the other actions that you might do during the task, either intentionally or not!
After about a half-hour, I had the basic plan on how I would, with unlimited time and budget, test this process. Since I'm still learning, I needed to narrow this down to a more-simple item, and build on it. So I explored a bit more on my chosen site, and found a page that had only one item with the tag, and wrote down what I needed to type, and where, to automate this process.
Returning to the groups that I had asked if there were more exercises like this, I found that no one had found a page with these. I was disappointed - how are we going to be able to skill ourselves up, and let others who are looking at a career in software find the delight that is testing to me? I placed on social media that this might be a good addition to one of the sites, but except for a bit of support, I haven't seen it come up yet.
Even if you just challenge yourself, this is still a good idea. Take what you know, and in a limited environment, expand on it to see how much you can do within that framework. You may not find a serious issue, but may discover limits on yourself, your views, and your tools that need to be examined and evaluated for your future.