anchor.diff:  
     # Run an automated test suite in the given virtual network.
     # `driver' is the script that runs the network.
  -  runTests = driver:
  +  runTests = { driver, pos }:
       stdenv.mkDerivation {
         name = "vm-test-run-${driver.testName}";
   
  
positive.code:         '';
  
        passthru = driver.passthru;
      };
  
  
  
negative.code:       # Skip linting (mainly intended for faster dev cycles)
      , skipLint ? false
      , passthru ? {}
      , # For meta.position
        pos ? # position used in error messages and for meta.position
          (if t.meta.description or null != null
            then builtins.unsafeGetAttrPos "description" t.meta
            else builtins.unsafeGetAttrPos "testScript" t)
      , ...
      } @ t:
      let
  