develop

Synopsis#

Develop integration tests with Hot Restart.

patrol develop

To see all available options and flags, run patrol develop --help.

Description#

patrol develop makes the development of integration tests faster and more fun, thanks to Flutter's Hot Restart feature.

To run a test file with Hot Restart, specify the --target option:

patrol develop --target integration_test/example_test.dart

This performs a build of your app, so it's usually slow.

When the build completes and the app starts, Hot Restart becomes active after a short while. Once it is active, type R to trigger a Hot Restart.

Demo#

Caveats#

patrol develop is powerful, but it has some limitations. It's important to understand them to write correct tests.

Flutter apps consist of 2 parts: the native part and the Flutter part. Hot Restart restarts only the Flutter part of your app.

When you press R, the Flutter part of your app is restarted – your main() function is run again.

It's important to note that:

The native part of your app is not restarted
The app's data is not cleared
The app is not uninstalled

Below are a few common scenarios when state of your app will probably differ between the first and later Hot Restarts.

No support for physical iOS

Patrol's Hot Restart is very unreliable when running on physical iOS devices, to the point that we consider it completely broken. This is unfortunate, but it's a bug on the Flutter's side.

Permissions

Once granted, a permissions cannot be revoked.

You have to work around this by handling both cases (of granted and not granted permissions) in your tests.

Removing all permissions at the beginning of each test won't work - both iOS and Android kill the app when any permission is revoked, and when the app dies, Hot Restart stops.

File system

The files your app creates in its internal storage aren't cleared between hot restarts.

For example, when some data is saved to SharedPreferences during the first restart, it will stay around in subsequent restarts (unless it's manually cleared).

The same goes for any data the app creates during test - photos, documents, etc. It's your responsibility to clean them up at the right time to have a stable environment during patrol develop.

Native state

If your app has some native code that runs only when the app is first run, it won't be re-executed on hot restarts.

These cases are quite specific and it's hard to give advice without knowing the context.