A toggle is a switch that has two positions, on and off. It can be used to control any setting or behavior, like switching between screens as you video chat with two friends at once. It can also be used to alternate between different behaviors such as the map or stream view in a web application.
Unlike checkboxes, which can have an indeterminate state, toggles are clearly defined as either On or Off. They can be used in conjunction with other controls like buttons and radio buttons. For example, the radio button on a form can be toggled with a text field so the user can choose between On and Off. Toggle switches are commonly used in modern interfaces but can sometimes be made inaccessible, for example by using a background color which makes the switch hard to see or by hiding the labels for On and Off. To avoid this, use accessibility best practices when designing toggles and ensure that there is a clear distinction between On and Off.
While toggles offer a number of advantages they can also be difficult to manage and test because the configuration for each toggle is baked into the release and cannot be changed without redeploying that release (or worse, rebuilding from scratch). Toggle management techniques range from simple but less dynamic approaches to more complex and sophisticated solutions which require a distributed configuration system.
In order to make testing toggles easier a good practice is to always use an approach which allows you to dynamically re-configure a specific service instance. This will allow you to exercise the current toggle configuration in your tests as well as test how a release will perform with all of its flags flipped Off. In some cases, this can even be done in a way which doesn’t require you to restart your entire testing environment!
Another important consideration when designing toggles is to consider the scalability and flexibility of your approach. For example, some teams prefer to hardcode toggles in their source code in a way that will prevent them from being re-configured by an automated tool such as a CD pipeline. This type of commenting can also be useful in helping to visualize which toggles have been active on a specific build or version of a product and can help with debugging.
Savvy teams also strive to keep their inventory of toggles under control. In particular, they are proactive about removing toggles that have been deemed ineffective or unnecessary. This is usually accomplished by adding a task to the team’s backlog for each new toggle that is added or by using more sophisticated strategies such as putting an “expiration date” on an Experiment Toggle to trigger a manual removal of that toggle at some future point in time. Some teams even go as far as to include a test in their CI/CD process that will fail if a flag is still present after its expiration date!
