I tried Whizlabs while prepping for my Snowflake certification exam and I was quite impressed with the content. Not only it had questions testing your understanding of the core concepts, it also had detailed explanation for each of the options. Besides the practice tests, it also offers video courses and sandboxes for coding practice to provide seamless hands-on experience.
I would definitely recommend Whizlabs to anyone who is seriously looking for great practice content for certification exams.