test-utilities: version test

Extract 'version test' to a reusable test utility as discussed in
https://github.com/NixOS/nixpkgs/pull/119636#issuecomment-826137021 and

pkgs/applications/graphics/ImageMagick/7.0.nix

@@ -2,6 +2,7 @@
 , bzip2, zlib, libX11, libXext, libXt, fontconfig, freetype, ghostscript, libjpeg, djvulibre
 , lcms2, openexr, libpng, librsvg, libtiff, libxml2, openjpeg, libwebp, libheif
 , ApplicationServices
+, testVersion, imagemagick
 }:
 
 let
@@ -72,6 +73,9 @@ stdenv.mkDerivation rec {
     done
   '';
 
+  passthru.tests.version =
+    testVersion { package = imagemagick; };
+
   meta = with lib; {
     homepage = "http://www.imagemagick.org/";
     description = "A software suite to create, edit, compose, or convert bitmap images";