Check, re-check, then check again.
Testing
Software lives in a world that keeps changing: operating systems, browsers, libraries and the needs of the people using it. Without thorough, frequent testing, even good software starts out with expensive bugs or picks them up over time. We keep it in working order however old it is and however many changes it has seen.
Unit testing
Everything we write ships with unit tests: small, precise checks that each piece behaves as intended. Written by the developer who wrote the code, they double as documentation of how each part is supposed to work and make it easy for anyone to pick the code up later.
Integration testing
Integration tests put finished pieces together and check that they work as a whole. The focus widens from whether a single function works to whether the system meets the business need, including the requirements that are not about any one feature.
End-to-end testing
End-to-end tests drive the real product the way a person would, in a real browser: signing in, filling in forms, paying, uploading. They catch the problems that only show up when everything is running together.
Acceptance testing
Before anything is called done, it is checked against what you asked for. If you have your own QA team, we work with them; if you don't, we walk you through it.