hello: Define a passthru test via new mkDerivation self arg

pkgs/applications/misc/hello/default.nix

@@ -1,4 +1,5 @@
 { lib
+, runCommand
 , stdenv
 , fetchurl
 , nixos
@@ -6,12 +7,12 @@
 , hello
 }:
 
-stdenv.mkDerivation rec {
+stdenv.mkDerivation (self: {
   pname = "hello";
   version = "2.12";
 
   src = fetchurl {
-    url = "mirror://gnu/hello/${pname}-${version}.tar.gz";
+    url = "mirror://gnu/hello/${self.pname}-${self.version}.tar.gz";
     sha256 = "1ayhp9v4m4rdhjmnl2bq3cibrbqqkgjbl3s7yk2nhlh8vj3ay16g";
   };
 
@@ -27,6 +28,13 @@ stdenv.mkDerivation rec {
         (nixos { environment.noXlibs = true; }).pkgs.hello;
   };
 
+  passthru.tests.run = runCommand "hello-test-run" {
+    nativeBuildInputs = [ self ];
+  } ''
+    diff -U3 --color=auto <(hello) <(echo 'Hello, world!')
+    touch $out
+  '';
+
   meta = with lib; {
     description = "A program that produces a familiar, friendly greeting";
     longDescription = ''
@@ -34,9 +42,9 @@ stdenv.mkDerivation rec {
       It is fully customizable.
     '';
     homepage = "https://www.gnu.org/software/hello/manual/";
-    changelog = "https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v${version}";
+    changelog = "https://git.savannah.gnu.org/cgit/hello.git/plain/NEWS?h=v${self.version}";
     license = licenses.gpl3Plus;
     maintainers = [ maintainers.eelco ];
     platforms = platforms.all;
   };
-}
+})