XState has an awesome package @xstate/test, which allows you to make your machine test providers.
You can create test models from your existing machines and treat it like "unit-testing" of your machines.
However, I prefer a different approach, when you create a separate machine for e2e-testing, which describes all of the possible user interactions with flows, like MachineUserFlow.
The event-based nature of state machines just fits perfectly with how users interact with the applications.
Be aware that @xstate/test is still in beta stage, so docs may be outdated or not correct. Refer to test examples to see actual tests.