How can I instantiate an Azure function in e.g. integration tests through dependency injection?

Consider the following function:

public class CheckApplications(IGovernanceService governanceService, ILogger<CheckApplications> logger)
{
    [Function(nameof(CheckApplications))]
    public async Task CheckApplicationsTimerTrigger(
        [TimerTrigger("0 0 12 * * *", RunOnStartup = false)] TimerInfo myTimer,
        FunctionContext context,
        CancellationToken cancellationToken)
    {
        ...
    }
}

As there is no Microsoft.AspNetCore.Mvc.Testing package for Azure functions, I want to integration test my functions by instantiating them in code.

However, I can't see that the individual functions are present in the service collection, so how would I instantiate them in this case?