An example app used for a really great Elixir testing training! This application is "complete" and "works". The thing is, it has bugs. Lots of bugs 🐛🐞🐛🐞🐛🐞
Our goal today is to find these bugs! If you have time and you want to you can try and fix them, but that's not actually the goal of the exercises today. Today we're just writing tests that will illustrate these bugs, and hopefully give us some really great error messages so we can have a really easy time fixing the bug (and get good information if we happen to introduce a regression in the future).
This application serves as an API for devices out in the world that send measurements to the application. There is no database backing the app - all information about these devices is stored in memory. These measurements can then be accessed in a web app to get data about the devices.
Devices can be registered, unregistered and configured. The configuration includes the following options:
- Is the device on or off?
- What type of measurements does it store?
- What is the maximum number of measurements a device should store for a certain type? For all types?
- Is there a warning threshold for a certain type of measurement?
- Does a device belong to a group of devices?
- Division by 0 error when calculating the average of an empty list.
- Measurements don't show up in views if there aren't any measurements, but should show that there are 0 measurements.
- Exception when trying to get information for a device that hasn't been registered.
- Adding a measurement to a type that hasn't been registered doesn't raise an error
- Triggering the alarm when a device is turned off shouldn't be possible because we shouldn't accept new measurements when the device is off
- Max number of measurements doesn't get updated when adding a new measurement type and so we go over the max number of all measurements
- Test crash and restart behavior for linked devices
- Improve tests in DeviceTests because they're flakey and not isolated
- UI only displays 3 measurement types even if a fourth is added.
- UI shows data for a device that is off even though it shouldn't.
- UI shows groups with the fewest devices first, but should show groups with the most devices first.
- Return 500 for the API because of malformed JSON (include a tuple or something that can't be encoded).
- Ensure the API never returns 500.
- Ensure that all webpages can always be rendered correctly in the UI.
- Ensure allowed actions for device states.
- Only config that can change when off is to turn it back on again
- No measurements are stored when the device is off
- We remain in a warning state when we've gone over the threshold until we've seen another measurement that is under the threshold
- We never exceed the max number of measurements (if set).
- We never have more than the max number of measurements after setting the max number of measurements.