Testing APIs before they are release and after they are released is a key part of the API lifecycle but one that is often left to chance. By treating testing as part of the development and building the test as the API evolves through the lifecycle API developers and APIProduct owners can release with more confidence. I will look at how functional testing, performance testing are key and need to be integrated in the Lifecycle and how using Mock service and virtual endpoints the developers and product owners can accelerate API consumption. I will also look at how testing promoting the testing into staging and production environments give a much richer developer experience as we track how the API is performing for our users.