add e2e testing (#167)

Reviewed-on: #167

linux/nix/default.nix

@@ -54,6 +54,52 @@
         };
 
       devShells.default = pkgs.callPackage ./devshell.nix { };
+
+      apps =
+        let
+          buildEnv = import ./build_env.nix { inherit pkgs lib; };
+          e2e = pkgs.writeShellApplication {
+            name = "nexus-e2e";
+            runtimeInputs =
+              buildEnv.packages
+              ++ (with pkgs; [
+                # TEMPORARY: matrix-continuwuity, once the local fixes are released
+                inputs.continuwuity.packages.${system}.default
+                curl
+                dbus
+              ]);
+            runtimeEnv = buildEnv.env;
+            text = builtins.readFile ./e2e.sh;
+          };
+        in
+        {
+          e2e = {
+            type = "app";
+            program = lib.getExe e2e;
+          };
+
+          e2e-headless = {
+            type = "app";
+            program = lib.getExe (
+              pkgs.writeShellApplication {
+                name = "nexus-e2e-headless";
+                runtimeInputs = [ pkgs.cage ];
+                runtimeEnv = {
+                  WLR_BACKENDS = "headless";
+                  __EGL_VENDOR_LIBRARY_FILENAMES = "${pkgs.mesa}/share/glvnd/egl_vendor.d/50_mesa.json";
+                };
+                text = ''
+                  unset DISPLAY WAYLAND_DISPLAY
+                  # Wayland needs one, which CI may not have
+                  XDG_RUNTIME_DIR="''${XDG_RUNTIME_DIR:-$(mktemp -d)}"
+                  export XDG_RUNTIME_DIR
+
+                  exec cage -- ${lib.getExe e2e} "$@"
+                '';
+              }
+            );
+          };
+        };
     };
 
   flake.nixosModules.default = import ./module.nix self;