What are the principles of an API test design?

Here, are the seven principles of API test design.

Exhaustive Testing: Exhaustive testing is not possible. Instead we need optimal amount of testing which is based on the risk assessment of the application.
Defect Clustering: Defect Clustering states that a small number of modules contain the most of the defect detected. Approximately 80% of the defect found in 20% of the modules. By experience we can identify such risky modules. But this approach has its own problems. If the same tests are repeated over and over again, eventually the same test case will no longer find new bugs.
Pesticide Paradox: Testers cannot depend on existing technique. They must have to look continually to improve the existing method to make testing more effective. But even all these hard work in testing we can never claim our product is bug free. To overcome this, test cases need to be regularly reviewed and revised add new and different test cases to help find more defects.
Testing shows presence of defects: Testing principle states that- testing talks about the presence of defects not about the absence of defect. Software testing reduces the probability of undiscovered defects remaining in the software but even if no defects found, it is not a proof of correctness.
But if we work hard, taking all precautions and make our software products 99% bug free. The software does not meet the needs and requirements of the client.
Absence of error -fallacy: This can be possible the software which is 99% bug free is still unusable. The case can be if the system is tested for the wrong requirement. Software testing is not finding the defects but also to check that software addresses the business needs. The absence of error is fallacy i.e. finding and fixing defects does not help if the system build is unusable and doesn’t fulfill the user’s needs and requirements.
Early Testing: Testing should start as soon as possible in the software development lifecycle. So that defects in the requirement or design phase captured in the early stages. It is cheaper to fix defect in the early stages of testing. We should start finding the bug at the moment the requirements are defined.
Testing is context dependent: Testing is context dependent that we test an e-commerce site will be different from the way we test the commercial. All the developed software’s are not identical. We will use different methodology; techniques and type of testing depend on the application type.