Replace vm tests with native tests about services-flake HOT 4 CLOSED

testScript can itself be a service that depends on the service that it testing. The testScript service should only start in CI.

Good idea! Once this PR is merged it will be super easy to run tests within process compose: once test process completes, other processes will be stopped and PC will exit with the code returned by the test process.

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Another approach

testScript can itself be a service that depends on the service that it testing. The testScript service should only start in CI.

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Note: this is mostly upstream work Platonic-Systems/process-compose-flake#36

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I have been thinking of different ways to implement this.

I have an idea and that involves having a testScript option for every service (resolves #33).

{
  testScript = lib.mkOption {
    type = types.nullOr (types.functionTo types.package);
    default = null;
    description = ''
      A package that contains a script to test the database.
      The script will be run after the database has been initialized.
    '';
    example = lib.literalExpression
    ''
      package: pkgs.writeShellApplication {
        name = "test-postgres";
        text = "echo 'SELECT version();' | ${package} -h 127.0.0.1";
      };
    '';
  };
}

The option will be used to create a process that will execute the testScript and end with whatever exit code the script returns (courtesy exit_on_end).

{
  "${name}-test" = lib.mkIf (config.testScript != null) {
    command = config.testScript config.package;
    depends_on."${name}".condition = "process_healthy";
    availability.exit_on_end = true;
  };
}

All looks good until we have more than one process that has a testScript, in that case whichever script executes first will be ran and all the other processes are immediately shutdown because exit_on_end waits for no one. I was thinking of a possible way to go around this by having a parent process that will use exit_on_end and this process will depend on all the testScripts. The parent process will have to somehow return the exit code 0 if all the testScripts ran successfully or the non-zero exit code of the first process that fails. I can't think of any way this can be done, any suggestions?

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