anchor.diff:            url = "https://github.com/purescript/purescript-tailrec.git";
             rev = "69f4625969e313203028968e4a9f743fa7f87883";
             sha256 = "0z7k80nl8dgv8mc2w8xsl2n0637bd1l8ppxak8kaifgjjwa81hx3";
  +        };
  +        phases = "installPhase";
  +        installPhase = "ln -s $src $out";
  +      };
  +
  +    "test-unit" = pkgs.stdenv.mkDerivation {
  +        name = "test-unit";
  +        version = "v15.0.0";
  +        src = pkgs.fetchgit {
  +          url = "https://github.com/bodil/purescript-test-unit.git";
  +          rev = "351c55b632e0c0ebffae05837909995a03de3406";
  +          sha256 = "06lb90vppa7naqqwz7wbvlkkyz86pbdd3ycw3d2iygvxbzkz8xjn";
           };
           phases = "installPhase";
           installPhase = "ln -s $src $out";
  
positive.code:         installPhase = "ln -s $src $out";
        };
  
      "functions" = pkgs.stdenv.mkDerivation {
          name = "functions";
          version = "v4.0.0";
  
negative.code:         installPhase = "ln -s $src $out";
        };
  
      "avar" = pkgs.stdenv.mkDerivation {
          name = "avar";
          version = "v3.0.0";
          src = pkgs.fetchgit {
            url = "https://github.com/slamdata/purescript-avar.git";
            rev = "17914413130490318a475e9de6a9244aaaa097d2";
            sha256 = "14g05jm2xricy5b9vn4k4lhc9lzi5jvpvv85h10s17kn4wwi9igk";
          };
          phases = "installPhase";
          installPhase = "ln -s $src $out";
        };
  
      "bifunctors" = pkgs.stdenv.mkDerivation {
          name = "bifunctors";
          version = "v4.0.0";
  