how to embed online compiler to website and give the user grade base on his code(like in codility)?

I want to build a website that contains a programming question and an editor so that the user can enter his code and based on some test cases the user will get grade, I would love to get direction on how to implement it right. I looked for API's and found paid products like Sphere-Engine or ones that didn't work already like HackerRank API but I couldn't find any working API. Just to make it clear I don't need the output of the code I need to run some test case on the code and then to give a grade for those who succeed like in (Codility). Are there any API's I can use ? or tool that I can embed to my website ?