After I passed a course and read other books on Algorithms, what really clicked Algorithms for me was this little known book: A Common Sense Guide to Data Structures and Algorithms by Jay Wengrow. This is what made Algorithms and Data Structures make sense to me.
There is only one real way to test, and the subject being CS, it is even more real: building things using those concepts.
For other subjects (and CS, too): demonstrate mastery with teaching others, producing something with the concepts learned and get feedback.
This way one can test true learning. And, even when tested this way, Spaced Repeatition really helps. I am speaking from experience.
When you are in a place where you can immerse yourself in a proper environment, like a college or work- where you hear terms and their usage regularly, learning becomes easier.
But when your environment is cut-off from the buzzing world, or everyone is doing ML and you want to do Cybersecurity, you can fake immersion using Anki. A good part of physical immersion can be replaced with using Anki.
Later I read DPV and it was great, too.