How to use Command Line Arguments in Swift Testing

Oscar de la Hera Gomez
Three flowers that represent Swift, Swift Testing and XCode side by side. Beneath them sits the text "Command Line Arguments".

Command line arguments allow you to launch an app with specific conditions, such as using SwiftData from memory or to test failed conditions.

The following tutorial shows how we found temporary files from our upcoming app Object Capture Pro. If you wish to be updated on the progress and release of this app, please subscribe using the link below.

A screenshot of the Struct of strings that we use to hold Command Line Arguments.

We recommend that you create a struct that holds the strings for the command line arguments that you will use through your application.

A screenshot of XCode showing how we used the argument to change the configuration of a SwiftData persistent container.

Within the code that you wish to alter, we recommend that you use a pattern similar to the one above, that uses DEBUG conditions that allows the code to work in a specific way if the flag is active.

A screenshot of a UITest showing how we launched an app with a Command Line Argument.

Then, within the UI Test, add the command line argument to the app.launchArguments.

Please note the launch arguments must be set before you launch the application.

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