Yes, testing hypotheticals is part of doing your research before posting a question. If you have a question along the lines of "What happens when I put a function call as the argument to another function call?" or "Can I use a negative index on a string?", you need to spend a little while trying it out, seeing what happens, and trying to understand the results.
If you can't explain the results of your experimentation, try a few variations. Try to search on the web for similar situations. See what you can see in the documentation. (Notice how similar this is to the process of debugging.)
Keep track of your everything you find, and when you finally give up, you'll have a really excellent Stack Overflow question.