Patrick Poulin, founder of API Fortress, argues that rigorous API testing is crucial but often neglected, as many developers rely solely on unit and smoke tests, which are inadequate for ensuring API quality. He emphasizes that APIs are generally up 99.99% of the time; however, the real issues arise from data contamination or inconsistencies that unit tests fail to detect. Poulin highlights the importance of validating API responses line-by-line, maintaining up-to-date documentation to alert consumers to changes, and using real data in live environments rather than simulations to ensure reliability. He advocates for API testing to be as comprehensive as that of websites and mobile apps, using tools like API Fortress to facilitate this process.