Refactor tests to load flake inputs with flake-compat

This makes `nix fmt` just works and we no longer have to override flake
inputs.

tests/nixos-tests.nix

@@ -0,0 +1,70 @@
+{
+  self,
+  privateInputs,
+  system,
+  pkgs,
+}:
+let
+  # Hardware profile checks
+  blackList = [
+    # does import-from-derivation
+    "toshiba-swanky"
+    # uses custom nixpkgs config
+    "raspberry-pi-2"
+    # deprecated profiles
+    "framework"
+    "asus-zephyrus-ga402x"
+    "lenovo-yoga-7-14ARH7"
+  ];
+
+  aarch64Systems = [
+    "raspberry-pi-3"
+    "raspberry-pi-4"
+    "raspberry-pi-5"
+  ];
+
+  matchArch =
+    moduleName:
+    if builtins.elem moduleName aarch64Systems then
+      system == "aarch64-linux"
+    else
+      # TODO also add riscv64
+      system == "x86_64-linux";
+
+  modules = pkgs.lib.filterAttrs (
+    name: _: !(builtins.elem name blackList || pkgs.lib.hasPrefix "common-" name) && matchArch name
+  ) self.nixosModules;
+
+  buildProfile = import ./build-profile.nix;
+
+  unfreeNixpkgs = {
+    config = {
+      allowBroken = true;
+      allowUnfree = true;
+      nvidia.acceptLicense = true;
+    };
+    overlays = [ ];
+    inherit system;
+  };
+
+  nixpkgsUnstable = import privateInputs.nixos-unstable-small unfreeNixpkgs;
+  nixpkgsStable = import privateInputs.nixos-stable unfreeNixpkgs;
+
+  # Build checks for both unstable and stable
+  unstableChecks = pkgs.lib.mapAttrs' (
+    name: module:
+    pkgs.lib.nameValuePair "unstable-${name}" (buildProfile {
+      pkgs = nixpkgsUnstable;
+      profile = module;
+    })
+  ) modules;
+
+  stableChecks = pkgs.lib.mapAttrs' (
+    name: module:
+    pkgs.lib.nameValuePair "stable-${name}" (buildProfile {
+      pkgs = nixpkgsStable;
+      profile = module;
+    })
+  ) modules;
+in
+unstableChecks // stableChecks