anchor.diff:          _ -> print "fail"
       '';
   
  -    js = writeJSBin "test_writers" { libraries = [ nodePackages.semver ]; } ''
  +    js = writeJSBin "test_writers_js_bin" { libraries = [ nodePackages.semver ]; } ''
         var semver = require('semver');
   
         if (semver.valid('1.2.3')) {
  
positive.code:   passthru = { inherit writeTest bin simple; };
    meta.platforms = lib.platforms.all;
  } ''
    ${lib.concatMapStringsSep "\n" (test: writeTest "success" "${test}/bin/test_writers") (lib.attrValues bin)}
    ${lib.concatMapStringsSep "\n" (test: writeTest "success" test) (lib.attrValues simple)}
    ${lib.concatMapStringsSep "\n" (test: writeTest "success" test) (lib.attrValues path)}
  
    echo 'nix-writers successfully tested' >&2
    touch $out
  
negative.code:       }
      '';
  
      dash = writeDash "test_writers_dash" ''
       test '~' = '~' && echo 'success'
      '';
  
      haskell = writeHaskell "test_writers_haskell" { libraries = [ haskellPackages.acme-default ]; } ''
        import Data.Default
  
        int :: Int
  