Generate a full-length mock test at your level, built from the same question types as the real JLPT, and take it as often as you like. Every attempt is scored so you can watch your progress section by section.
These questions were written the same way as every question in the mock tests, one for each level and each a different question type: listen to a recording, read a notice, or solve a word-order puzzle. Pick a level, choose an answer and check it to see the explanation, exactly as you would after a full test.
Before each test you will see the official time limit for every part. Sit it as Practice at your own pace, or under Exam conditions to be timed to those limits.
A generated test is yours to keep. Take it again after studying the questions you missed and compare the scores.
The real JLPT needs a minimum score in every section, not just a good total. Your progress shows each section so no weak spot hides behind a strong one.