diff --git a/tests/modules/programs/firefox/common.nix b/tests/modules/programs/firefox/common.nix
index a9c04d57bc..46663547d8 100644
--- a/tests/modules/programs/firefox/common.nix
+++ b/tests/modules/programs/firefox/common.nix
@@ -1,11 +1,22 @@
-name:
+{ lib, name }:
+let
+  withDefaultStateVersion = module: {
+    imports = [ module ];
+
+    # Stronger than the global test default, but weaker than any test-local
+    # stateVersion assignment.
+    home.stateVersion = lib.mkOverride 900 "26.05";
+  };
+in
 builtins.mapAttrs
   (
     _test: module:
-    import module [
-      "programs"
-      name
-    ]
+    withDefaultStateVersion (
+      import module [
+        "programs"
+        name
+      ]
+    )
   )
   {
     "${name}-deprecated-native-messenger" = ./deprecated-native-messenger.nix;
diff --git a/tests/modules/programs/firefox/default.nix b/tests/modules/programs/firefox/default.nix
index 5eb4be1cba..f3379b44f8 100644
--- a/tests/modules/programs/firefox/default.nix
+++ b/tests/modules/programs/firefox/default.nix
@@ -1,3 +1,4 @@
+{ lib, ... }:
 {
   "firefox-config-path-explicit-legacy" = ./config-path-explicit-legacy.nix;
   "firefox-config-path-explicit-xdg" = ./config-path-explicit-xdg.nix;
@@ -5,6 +6,6 @@
   "firefox-config-path-warning" = ./config-path-warning.nix;
   "firefox-multiple-derivatives" = ./multiple-derivatives.nix;
 }
-// (import ./firefox.nix)
-// (import ./floorp.nix)
-// (import ./librewolf.nix)
+// (import ./firefox.nix { inherit lib; })
+// (import ./floorp.nix { inherit lib; })
+// (import ./librewolf.nix { inherit lib; })
diff --git a/tests/modules/programs/firefox/final-package.nix b/tests/modules/programs/firefox/final-package.nix
index 19c1037fa2..f26cae53e0 100644
--- a/tests/modules/programs/firefox/final-package.nix
+++ b/tests/modules/programs/firefox/final-package.nix
@@ -22,8 +22,6 @@ lib.mkIf config.test.enableBig (
     }
   )
   // {
-    home.stateVersion = "19.09";
-
     _module.args.pkgs = lib.mkForce realPkgs;
 
     nmt.script = ''
diff --git a/tests/modules/programs/firefox/firefox.nix b/tests/modules/programs/firefox/firefox.nix
index dd126e260b..80b77ffb2f 100644
--- a/tests/modules/programs/firefox/firefox.nix
+++ b/tests/modules/programs/firefox/firefox.nix
@@ -1 +1,5 @@
-import ./common.nix "firefox"
+{ lib, ... }:
+import ./common.nix {
+  inherit lib;
+  name = "firefox";
+}
diff --git a/tests/modules/programs/firefox/floorp.nix b/tests/modules/programs/firefox/floorp.nix
index 67a13659c1..6cd18447f2 100644
--- a/tests/modules/programs/firefox/floorp.nix
+++ b/tests/modules/programs/firefox/floorp.nix
@@ -1 +1,5 @@
-import ./common.nix "floorp"
+{ lib, ... }:
+import ./common.nix {
+  inherit lib;
+  name = "floorp";
+}
diff --git a/tests/modules/programs/firefox/librewolf.nix b/tests/modules/programs/firefox/librewolf.nix
index 3a77e0f1d4..cbb3c3ba3c 100644
--- a/tests/modules/programs/firefox/librewolf.nix
+++ b/tests/modules/programs/firefox/librewolf.nix
@@ -1 +1,5 @@
-import ./common.nix "librewolf"
+{ lib, ... }:
+import ./common.nix {
+  inherit lib;
+  name = "librewolf";
+}
diff --git a/tests/modules/programs/firefox/multiple-derivatives.nix b/tests/modules/programs/firefox/multiple-derivatives.nix
index 12a35de70f..c6b6c5c797 100644
--- a/tests/modules/programs/firefox/multiple-derivatives.nix
+++ b/tests/modules/programs/firefox/multiple-derivatives.nix
@@ -1,6 +1,8 @@
 { config, lib, ... }:
 
 lib.mkIf config.test.enableBig {
+  home.stateVersion = "26.05";
+
   programs.firefox = {
     enable = true;
     package = null;
diff --git a/tests/modules/programs/firefox/policies.nix b/tests/modules/programs/firefox/policies.nix
index e447498f4c..23b6a7ad5f 100644
--- a/tests/modules/programs/firefox/policies.nix
+++ b/tests/modules/programs/firefox/policies.nix
@@ -16,10 +16,7 @@ in
   imports = [ firefoxMockOverlay ];
 
   config = lib.mkIf config.test.enableBig (
-    {
-      home.stateVersion = "23.05";
-    }
-    // lib.setAttrByPath modulePath {
+    lib.setAttrByPath modulePath {
       enable = true;
       configPath = lib.mkIf pkgs.stdenv.hostPlatform.isLinux ".mozilla/firefox";
       policies = {
@@ -40,9 +37,17 @@ in
             else
               "${cfg.finalPackage}/lib/${cfg.finalPackage.unwrapped.libName or cfg.wrappedPackageName}";
           config_file = "${libDir}/distribution/policies.json";
+          config_file_browser = "${libDir}/browser/distribution/policies.json";
         in
         ''
           jq=${lib.getExe pkgs.jq}
+          if [[ -f "${config_file}" ]]; then
+            config_file="${config_file}"
+          elif [[ -f "${config_file_browser}" ]]; then
+            config_file="${config_file_browser}"
+          else
+            fail "Expected ${libDir}/distribution/policies.json to exist but it was not found."
+          fi
 
           assertFileExists "${config_file}"
 
diff --git a/tests/modules/programs/firefox/profiles/bookmarks/default.nix b/tests/modules/programs/firefox/profiles/bookmarks/default.nix
index 3001e6ead8..14a098f719 100644
--- a/tests/modules/programs/firefox/profiles/bookmarks/default.nix
+++ b/tests/modules/programs/firefox/profiles/bookmarks/default.nix
@@ -18,11 +18,7 @@ in
   imports = [ firefoxMockOverlay ];
 
   config = lib.mkIf config.test.enableBig (
-    {
-      # Required for bookmark policy to get set
-      home.stateVersion = "19.09";
-    }
-    // lib.setAttrByPath modulePath {
+    lib.setAttrByPath modulePath {
       enable = true;
       configPath = lib.mkIf pkgs.stdenv.hostPlatform.isLinux ".mozilla/firefox";
       profiles.bookmarks = {
@@ -95,8 +91,17 @@ in
             else
               "${cfg.finalPackage}/lib/${cfg.finalPackage.unwrapped.libName or cfg.wrappedPackageName}";
           config_file = "${libDir}/distribution/policies.json";
+          config_file_browser = "${libDir}/browser/distribution/policies.json";
         in
         ''
+          if [[ -f "${config_file}" ]]; then
+            config_file="${config_file}"
+          elif [[ -f "${config_file_browser}" ]]; then
+            config_file="${config_file_browser}"
+          else
+            fail "Expected ${libDir}/distribution/policies.json to exist but it was not found."
+          fi
+
           assertFileExists "${config_file}"
 
           noDefaultBookmarks_actual_value="$(${lib.getExe pkgs.jq} ".policies.NoDefaultBookmarks" ${config_file})"
diff --git a/tests/modules/programs/firefox/profiles/overwrite/default.nix b/tests/modules/programs/firefox/profiles/overwrite/default.nix
index 1dcfa35f90..24e094b2c7 100644
--- a/tests/modules/programs/firefox/profiles/overwrite/default.nix
+++ b/tests/modules/programs/firefox/profiles/overwrite/default.nix
@@ -46,7 +46,7 @@ in
         in
         ''
           assertFileRegex \
-            "home-path/${binPath}/${cfg.wrappedPackageName}" \
+            "home-path/${binPath}/${cfg.finalPackage.meta.mainProgram}" \
             MOZ_APP_LAUNCHER
 
           assertDirectoryExists "home-files/${cfg.profilesPath}/basic"
diff --git a/tests/modules/programs/firefox/profiles/settings/default.nix b/tests/modules/programs/firefox/profiles/settings/default.nix
index b87f09c2c8..b99cb9a2b8 100644
--- a/tests/modules/programs/firefox/profiles/settings/default.nix
+++ b/tests/modules/programs/firefox/profiles/settings/default.nix
@@ -48,7 +48,7 @@ in
         in
         ''
           assertFileRegex \
-            "home-path/${binPath}/${cfg.wrappedPackageName}" \
+            "home-path/${binPath}/${cfg.finalPackage.meta.mainProgram}" \
             MOZ_APP_LAUNCHER
 
           assertDirectoryExists "home-files/${cfg.profilesPath}/basic"
diff --git a/tests/modules/programs/firefox/profiles/userchrome/default.nix b/tests/modules/programs/firefox/profiles/userchrome/default.nix
index f1b01c642d..091271113f 100644
--- a/tests/modules/programs/firefox/profiles/userchrome/default.nix
+++ b/tests/modules/programs/firefox/profiles/userchrome/default.nix
@@ -44,7 +44,7 @@ in
         in
         ''
           assertFileRegex \
-            "home-path/${binPath}/${cfg.wrappedPackageName}" \
+            "home-path/${binPath}/${cfg.finalPackage.meta.mainProgram}" \
             MOZ_APP_LAUNCHER
 
           assertDirectoryExists "home-files/${cfg.profilesPath}/basic"
diff --git a/tests/modules/programs/firefox/setup-firefox-mock-overlay.nix b/tests/modules/programs/firefox/setup-firefox-mock-overlay.nix
index 04fffd244d..efa982b2f1 100644
--- a/tests/modules/programs/firefox/setup-firefox-mock-overlay.nix
+++ b/tests/modules/programs/firefox/setup-firefox-mock-overlay.nix
@@ -25,7 +25,7 @@ in
           binaryName = cfg.wrappedPackageName;
           gtk3 = null;
           meta.description = "I pretend to be ${cfg.name}";
-          meta.mainProgram = lib.toLower cfg.name;
+          meta.mainProgram = cfg.wrappedPackageName;
         };
         outPath = null;
         buildScript =