It definitely helps to start with an environment where tests are easy to write, so that you can focus on the principles of testing without having to learn a lot of mechanics.
Python's built-in "unittest" module is an example of that. While it's not perfect, you can quickly form good habits by using it.
And it is not limited to Python. For instance, I've written unittest-compatible classes that basically run other programs as test cases. Either way, you're forced to think about things like "how do I automatically detect that this failed?" and "is the purpose of this test clear?".
Python's built-in "unittest" module is an example of that. While it's not perfect, you can quickly form good habits by using it.
And it is not limited to Python. For instance, I've written unittest-compatible classes that basically run other programs as test cases. Either way, you're forced to think about things like "how do I automatically detect that this failed?" and "is the purpose of this test clear?".