Every serverless developer knows the feeling. You change a line in a handler. You push. You wait. You open CloudWatch, squint at a log line, and realize the code is still wrong. So you change it again. Push. Wait. Check. Repeat.
That loop is a hidden tax on your productivity. And unlike a slower database or a bulky framework, you barely notice it because it has always been there.
When you test on AWS itself, every change costs you two things at once: time and money.
The worst part is the loop is also a context tax. By the time your deploy comes back, you have lost your train of thought. You are not debugging anymore, you are waiting.
What if the code you test locally was the exact code you deploy? No emulator. No mock runtime. No waiting on CloudFormation to check a log line.
That is the idea behind LambdaLoop. It boots your actual Lambda handler on your machine, feeds it real event payloads, and runs Given-When-Then tests against it.
pip install lambdaloop
lambdaloop run --handler app.handler --event event.json
lambdaloop test --handler app.handler --tests tests/Change a line, run the test, know in seconds whether it works. The feedback loop that used to take minutes now takes seconds.
When you shift testing local, a few things change fast: