firefox-esr-91: init at 91.0esr

(cherry picked from commit d5f7fc95a9ec5798618d10fd04a3ef91aa08de76)

nixos/tests/all-tests.nix

@@ -123,8 +123,9 @@ in
   fancontrol = handleTest ./fancontrol.nix {};
   fcitx = handleTest ./fcitx {};
   ferm = handleTest ./ferm.nix {};
-  firefox = handleTest ./firefox.nix {};
-  firefox-esr = handleTest ./firefox.nix { esr = true; };
+  firefox = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox; };
+  firefox-esr-78 = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox-esr-78; };
+  firefox-esr-91 = handleTest ./firefox.nix { firefoxPackage = pkgs.firefox-esr-91; };
   firejail = handleTest ./firejail.nix {};
   firewall = handleTest ./firewall.nix {};
   fish = handleTest ./fish.nix {};

nixos/tests/firefox.nix

@@ -1,4 +1,4 @@
-import ./make-test-python.nix ({ pkgs, esr ? false, ... }: {
+import ./make-test-python.nix ({ pkgs, firefoxPackage, ... }: {
   name = "firefox";
   meta = with pkgs.lib.maintainers; {
     maintainers = [ eelco shlevy ];
@@ -8,9 +8,10 @@ import ./make-test-python.nix ({ pkgs, esr ? false, ... }: {
     { pkgs, ... }:
 
     { imports = [ ./common/x11.nix ];
-      environment.systemPackages =
-        (if esr then [ pkgs.firefox-esr ] else [ pkgs.firefox ])
-        ++ [ pkgs.xdotool ];
+      environment.systemPackages = [
+        firefoxPackage
+        pkgs.xdotool
+      ];
 
       # Need some more memory to record audio.
       virtualisation.memorySize = "500";