Infection VS slim4-skeleton

Obviously, we can not generate mutants manually. For that purpose, there are mutation testing utilities. For PHP, we have Infection.

Infection: PHP Mutation Testing library. Plugins: roave/infection-static-analysis-plugin: Static analysis on top of mutation testing - prevents escaped mutants from being invalid according to static analysis bitexpert/captainhook-infection: Captain Hook Plugin to run InfectionPHP only against the changed files of a commit

Infection: PHP Mutation Testing library. Plugins: roave/infection-static-analysis-plugin: Static analysis on top of mutation testing - prevents escaped mutants from being invalid according to static analysis bitexpert/captainhook-infection: Captain Hook Plugin to run InfectionPHP only against the changed files of a commit

If you want to enforce testing automatically probably the best option is to rely on mutation testing, using Infection. That doesn't just check that the tests cover the code, it checks that if the code was different to what it is then the tests would (usually) fail.

IMO code coverage is a very flawed metric on its own. A high percentage doesn't guarantee that the tests actually test the right things, and it would be much more efficient if mutation testing was used (e.g. Infection). It still uses the generated code coverage reports, but only as a base for its own metrics.

For your last edit - you can also add infection which will infect your code with other values, like if you expect a positive number, it will try and inject a negative number - and see what happens - does your code break everything or something. Also it will try to inject false where you might expect a true and many many other things, and yes you will get some weird results from infection, but its a good thing to look at, and atleast check the logs and see why the infection failed at a test.

The only one that I've used is infection for PHP.

That's practically a light form of mutant testing. Have you checked Infection?

You can have the container call in a config folder with a file called dependencies or how ever you want. A few existing examples of this is here - Slim calls this app/dependencies in this skeleton project and Odan's Skeleton has this as config/container in their project.

Yes, as an example, the First Application's business logic (not that it's much) doesn't tie itself to the framework, as one example. Odan's Slim Skeleton, ADR Example (yes, I know you are the author), and the Aura Payload example class can be seen as other examples.

Even just the tests in your first link are very useful to see, such as: https://github.com/odan/slim4-skeleton/blob/master/tests/TestCase/Action/Customer/CustomerCreatorActionTest.php

Another option, to me and speaking to the OP as an alternative, it is simpler to add some Data Mappers/Repositories to abstract away the Database code. Good examples is the sample ADR application, Payload library example, Slim 3 First Application, or this Slim 4 Skeleton application

You could also use a Slim Skeleton like Odan's which incorporates much more features to help - docs.

Try Slim again. The setup may be too much, but the concept is the same. Look at the first application or any of the skeleton apps to help (https://github.com/odan/slim4-skeleton for one).