anchor.diff:  
     passthru = {
       shellPath = "/bin/elvish";
  +    tests = runCommand "${pname}-buildinfo-test" {} ''
  +      mkdir $out
  +
  +      ${elvish}/bin/elvish -c "
  +        fn expect {|key expected|
  +          var actual = \$buildinfo[\$key]
  +          if (not-eq \$actual \$expected) {
  +            fail '\$buildinfo['\$key']: expected '(to-string \$expected)', got '(to-string \$actual)
  +          }
  +        }
  +
  +        expect version ${version}
  +        expect reproducible \$true
  +      "
  +    '';
     };
   }
  
positive.code: 
    subPackages = [ "cmd/elvish" ];
  
    ldflags = [ "-s" "-w" "-X github.com/elves/elvish/pkg/buildinfo.Version==${version}" "-X github.com/elves/elvish/pkg/buildinfo.Reproducible=true" ];
  
    src = fetchFromGitHub {
      owner = "elves";
  
negative.code: { lib, buildGoModule, fetchFromGitHub, runCommand, elvish }:
  
  buildGoModule rec {
    pname = "elvish";
  