A blog by James Espie

Testing in production using circuit breakers

30 days of Testability, day twelve

Circuit breakers

Today’s exercise:

Decomposability is an important part of testability. Complete our circuit breakers testing exercise over on The Club!

The ‘circuit breakers’ exercise is to take a piece of software, and see how you might apply a ‘circuit breaker’ to it.

Circuit breakers are a concept borrowed from electronics. If there is a fault detected in a circuit (like an overload), interrupt what the circuit is doing. This minimises any damage caused.

We can do the same thing in software. Run a function, but if a fault is detected, stop running that function (and do something else).

This is really useful for testing - it means you can test something in production, and have a failsafe if it goes awry!

I won’t go into too much more detail, I’ve written another article on it over on Ministry of Testing.

Quiz time!

To do the exercise, I got together with my friend Sonia. We tried to see if we could apply the circuit breaker model to the Stuff Quiz.

It’s a bit of an over-the-top example, but, it was a fun excuse to do the quiz too :P

Watch us try and do the quiz, and talk about circuit breakers!


As always, thanks for watching! These posts are getting pretty delayed now, so, thanks for your patience too! We’ll make it to day thirty! And thanks Sonia for joining me!