diff --git a/tests/functional/build-remote-input-addressed.sh b/tests/functional/build-remote-input-addressed.sh
index 986692dbc..11199a408 100755
--- a/tests/functional/build-remote-input-addressed.sh
+++ b/tests/functional/build-remote-input-addressed.sh
@@ -23,7 +23,7 @@ EOF
     chmod +x "$TEST_ROOT/post-build-hook.sh"
     rm -f "$TEST_ROOT/post-hook-counter"
 
-    echo "post-build-hook = $TEST_ROOT/post-build-hook.sh" >> "$NIX_CONF_DIR/nix.conf"
+    echo "post-build-hook = $TEST_ROOT/post-build-hook.sh" >> "$test_nix_conf"
 }
 
 registerBuildHook
diff --git a/tests/functional/common/init.sh b/tests/functional/common/init.sh
index 4f2a393af..19cef5af9 100755
--- a/tests/functional/common/init.sh
+++ b/tests/functional/common/init.sh
@@ -1,5 +1,30 @@
 # shellcheck shell=bash
 
+# for shellcheck
+: "${test_nix_conf_dir?}" "${test_nix_conf?}"
+
+if isTestOnNixOS; then
+
+  mkdir -p "$test_nix_conf_dir" "$TEST_HOME"
+
+  export NIX_USER_CONF_FILES="$test_nix_conf_dir/nix.conf"
+  mkdir -p "$test_nix_conf_dir" "$TEST_HOME"
+  ! test -e "$test_nix_conf"
+  cat > "$test_nix_conf_dir/nix.conf" <<EOF
+experimental-features = nix-command flakes
+flake-registry = $TEST_ROOT/registry.json
+show-trace = true
+EOF
+
+  # When we're doing everything in the same store, we need to bring
+  # dependencies into context.
+  sed -i "$(dirname "${BASH_SOURCE[0]}")"/../config.nix \
+    -e 's^\(shell\) = "/nix/store/\([^/]*\)/\(.*\)";^\1 = builtins.appendContext "/nix/store/\2" { "/nix/store/\2".path = true; } + "/\3";^' \
+    -e 's^\(path\) = "/nix/store/\([^/]*\)/\(.*\)";^\1 = builtins.appendContext "/nix/store/\2" { "/nix/store/\2".path = true; } + "/\3";^' \
+    ;
+
+else
+
 test -n "$TEST_ROOT"
 # We would delete any daemon socket, so let's stop the daemon first.
 killDaemon
@@ -41,3 +66,5 @@ EOF
 nix-store --init
 # Sanity check
 test -e "$NIX_STATE_DIR"/db/db.sqlite
+
+fi # !isTestOnNixOS
diff --git a/tests/functional/common/subst-vars.sh.in b/tests/functional/common/subst-vars.sh.in
index 4105e9f35..42ef30fb8 100644
--- a/tests/functional/common/subst-vars.sh.in
+++ b/tests/functional/common/subst-vars.sh.in
@@ -1,11 +1,14 @@
 # NOTE: instances of @variable@ are substituted as defined in /mk/templates.mk
 
-export PATH=@bindir@:$PATH
+if ! isTestOnNixOS; then
+  export SHELL="@bash@"
+  export PATH=@bindir@:$PATH
+fi
+
 export coreutils=@coreutils@
 #lsof=@lsof@
 
 export dot=@dot@
-export SHELL="@bash@"
 export PAGER=cat
 export busybox="@sandbox_shell@"
 
diff --git a/tests/functional/common/vars-and-functions.sh b/tests/functional/common/vars-and-functions.sh
index ad5b29a94..4b0fee5b2 100644
--- a/tests/functional/common/vars-and-functions.sh
+++ b/tests/functional/common/vars-and-functions.sh
@@ -6,6 +6,15 @@ if [[ -z "${COMMON_VARS_AND_FUNCTIONS_SH_SOURCED-}" ]]; then
 
 COMMON_VARS_AND_FUNCTIONS_SH_SOURCED=1
 
+isTestOnNixOS() {
+  [[ "${isTestOnNixOS:-}" == 1 ]]
+}
+
+die() {
+  echo "fatal error: $*" >&2
+  exit 1
+}
+
 set +x
 
 commonDir="$(readlink -f "$(dirname "${BASH_SOURCE[0]-$0}")")"
@@ -15,27 +24,35 @@ source "$commonDir/subst-vars.sh"
 : "${PATH?} ${coreutils?} ${dot?} ${SHELL?} ${PAGER?} ${busybox?} ${version?} ${system?} ${BUILD_SHARED_LIBS?}"
 
 export TEST_ROOT=$(realpath ${TMPDIR:-/tmp}/nix-test)/${TEST_NAME:-default/tests\/functional//}
-export NIX_STORE_DIR
-if ! NIX_STORE_DIR=$(readlink -f $TEST_ROOT/store 2> /dev/null); then
-    # Maybe the build directory is symlinked.
-    export NIX_IGNORE_SYMLINK_STORE=1
-    NIX_STORE_DIR=$TEST_ROOT/store
-fi
-export NIX_LOCALSTATE_DIR=$TEST_ROOT/var
-export NIX_LOG_DIR=$TEST_ROOT/var/log/nix
-export NIX_STATE_DIR=$TEST_ROOT/var/nix
-export NIX_CONF_DIR=$TEST_ROOT/etc
-export NIX_DAEMON_SOCKET_PATH=$TEST_ROOT/dSocket
-unset NIX_USER_CONF_FILES
-export _NIX_TEST_SHARED=$TEST_ROOT/shared
-if [[ -n $NIX_STORE ]]; then
-    export _NIX_TEST_NO_SANDBOX=1
-fi
-export _NIX_IN_TEST=$TEST_ROOT/shared
-export _NIX_TEST_NO_LSOF=1
-export NIX_REMOTE=${NIX_REMOTE_-}
-unset NIX_PATH
+test_nix_conf_dir=$TEST_ROOT/etc
+test_nix_conf=$test_nix_conf_dir/nix.conf
+
 export TEST_HOME=$TEST_ROOT/test-home
+
+if ! isTestOnNixOS; then
+  export NIX_STORE_DIR
+  if ! NIX_STORE_DIR=$(readlink -f $TEST_ROOT/store 2> /dev/null); then
+      # Maybe the build directory is symlinked.
+      export NIX_IGNORE_SYMLINK_STORE=1
+      NIX_STORE_DIR=$TEST_ROOT/store
+  fi
+  export NIX_LOCALSTATE_DIR=$TEST_ROOT/var
+  export NIX_LOG_DIR=$TEST_ROOT/var/log/nix
+  export NIX_STATE_DIR=$TEST_ROOT/var/nix
+  export NIX_CONF_DIR=$test_nix_conf_dir
+  export NIX_DAEMON_SOCKET_PATH=$TEST_ROOT/dSocket
+  unset NIX_USER_CONF_FILES
+  export _NIX_TEST_SHARED=$TEST_ROOT/shared
+  if [[ -n $NIX_STORE ]]; then
+      export _NIX_TEST_NO_SANDBOX=1
+  fi
+  export _NIX_IN_TEST=$TEST_ROOT/shared
+  export _NIX_TEST_NO_LSOF=1
+  export NIX_REMOTE=${NIX_REMOTE_-}
+
+fi # ! isTestOnNixOS
+
+unset NIX_PATH
 export HOME=$TEST_HOME
 unset XDG_STATE_HOME
 unset XDG_DATA_HOME
@@ -66,6 +83,10 @@ clearProfiles() {
 }
 
 clearStore() {
+    if isTestOnNixOS; then
+      die "clearStore: not supported when testing on NixOS. Is it really needed? If so add conditionals; e.g. if ! isTestOnNixOS; then ..."
+    fi
+
     echo "clearing store..."
     chmod -R +w "$NIX_STORE_DIR"
     rm -rf "$NIX_STORE_DIR"
@@ -84,6 +105,10 @@ clearCacheCache() {
 }
 
 startDaemon() {
+    if isTestOnNixOS; then
+      die "startDaemon: not supported when testing on NixOS. Is it really needed? If so add conditionals; e.g. if ! isTestOnNixOS; then ..."
+    fi
+
     # Don’t start the daemon twice, as this would just make it loop indefinitely
     if [[ "${_NIX_TEST_DAEMON_PID-}" != '' ]]; then
         return
@@ -110,6 +135,10 @@ startDaemon() {
 }
 
 killDaemon() {
+    if isTestOnNixOS; then
+      die "killDaemon: not supported when testing on NixOS. Is it really needed? If so add conditionals; e.g. if ! isTestOnNixOS; then ..."
+    fi
+
     # Don’t fail trying to stop a non-existant daemon twice
     if [[ "${_NIX_TEST_DAEMON_PID-}" == '' ]]; then
         return
@@ -130,6 +159,10 @@ killDaemon() {
 }
 
 restartDaemon() {
+    if isTestOnNixOS; then
+      die "restartDaemon: not supported when testing on NixOS. Is it really needed? If so add conditionals; e.g. if ! isTestOnNixOS; then ..."
+    fi
+
     [[ -z "${_NIX_TEST_DAEMON_PID:-}" ]] && return 0
 
     killDaemon
@@ -152,6 +185,12 @@ skipTest () {
     exit 99
 }
 
+TODO_NixOS() {
+    if isTestOnNixOS; then
+        skipTest "This test has not been adapted for NixOS yet"
+    fi
+}
+
 requireDaemonNewerThan () {
     isDaemonNewer "$1" || skipTest "Daemon is too old"
 }
@@ -234,7 +273,7 @@ buggyNeedLocalStore() {
 
 enableFeatures() {
     local features="$1"
-    sed -i 's/experimental-features .*/& '"$features"'/' "$NIX_CONF_DIR"/nix.conf
+    sed -i 's/experimental-features .*/& '"$features"'/' "$test_nix_conf_dir"/nix.conf
 }
 
 set -x
diff --git a/tests/functional/impure-env.sh b/tests/functional/impure-env.sh
index 3c7df169e..e65c78b00 100755
--- a/tests/functional/impure-env.sh
+++ b/tests/functional/impure-env.sh
@@ -20,13 +20,13 @@ startDaemon
 
 varTest env_name value --impure-env env_name=value
 
-echo 'impure-env = set_in_config=config_value' >> "$NIX_CONF_DIR/nix.conf"
+echo 'impure-env = set_in_config=config_value' >> "$test_nix_conf"
 set_in_config=daemon_value restartDaemon
 
 varTest set_in_config config_value
 varTest set_in_config client_value --impure-env set_in_config=client_value
 
-sed -i -e '/^trusted-users =/d' "$NIX_CONF_DIR/nix.conf"
+sed -i -e '/^trusted-users =/d' "$test_nix_conf"
 
 env_name=daemon_value restartDaemon
 
diff --git a/tests/functional/local-overlay-store/common.sh b/tests/functional/local-overlay-store/common.sh
index 0e6097861..bbe84847a 100644
--- a/tests/functional/local-overlay-store/common.sh
+++ b/tests/functional/local-overlay-store/common.sh
@@ -31,7 +31,7 @@ requireEnvironment () {
 }
 
 addConfig () {
-    echo "$1" >> "$NIX_CONF_DIR/nix.conf"
+    echo "$1" >> "$test_nix_conf"
 }
 
 setupConfig () {
diff --git a/tests/functional/post-hook.sh b/tests/functional/post-hook.sh
index c0b1ab3aa..7540d1045 100755
--- a/tests/functional/post-hook.sh
+++ b/tests/functional/post-hook.sh
@@ -7,7 +7,7 @@ clearStore
 rm -f $TEST_ROOT/result
 
 export REMOTE_STORE=file:$TEST_ROOT/remote_store
-echo 'require-sigs = false' >> $NIX_CONF_DIR/nix.conf
+echo 'require-sigs = false' >> $test_nix_conf
 
 restartDaemon
 
diff --git a/tests/nixos/default.nix b/tests/nixos/default.nix
index 710f8a273..2ab00b336 100644
--- a/tests/nixos/default.nix
+++ b/tests/nixos/default.nix
@@ -132,4 +132,11 @@ in
   ca-fd-leak = runNixOSTestFor "x86_64-linux" ./ca-fd-leak;
 
   gzip-content-encoding = runNixOSTestFor "x86_64-linux" ./gzip-content-encoding.nix;
+
+  functional_user = runNixOSTestFor "x86_64-linux" ./functional/as-user.nix;
+
+  functional_trusted = runNixOSTestFor "x86_64-linux" ./functional/as-trusted-user.nix;
+
+  functional_root = runNixOSTestFor "x86_64-linux" ./functional/as-root.nix;
+
 }
diff --git a/tests/nixos/functional/as-root.nix b/tests/nixos/functional/as-root.nix
new file mode 100644
index 000000000..96be3d593
--- /dev/null
+++ b/tests/nixos/functional/as-root.nix
@@ -0,0 +1,12 @@
+{
+  name = "functional-tests-on-nixos_root";
+
+  imports = [ ./common.nix ];
+
+  testScript = ''
+    machine.wait_for_unit("multi-user.target")
+    machine.succeed("""
+      run-test-suite >&2
+    """)
+  '';
+}
diff --git a/tests/nixos/functional/as-trusted-user.nix b/tests/nixos/functional/as-trusted-user.nix
new file mode 100644
index 000000000..d6f825697
--- /dev/null
+++ b/tests/nixos/functional/as-trusted-user.nix
@@ -0,0 +1,18 @@
+{
+  name = "functional-tests-on-nixos_trusted-user";
+
+  imports = [ ./common.nix ];
+
+  nodes.machine = {
+    users.users.alice = { isNormalUser = true; };
+    nix.settings.trusted-users = [ "alice" ];
+  };
+
+  testScript = ''
+    machine.wait_for_unit("multi-user.target")
+    machine.succeed("""
+      export TEST_TRUSTED_USER=1
+      su --login --command "run-test-suite" alice >&2
+    """)
+  '';
+}
\ No newline at end of file
diff --git a/tests/nixos/functional/as-user.nix b/tests/nixos/functional/as-user.nix
new file mode 100644
index 000000000..1443f6e6c
--- /dev/null
+++ b/tests/nixos/functional/as-user.nix
@@ -0,0 +1,16 @@
+{
+  name = "functional-tests-on-nixos_user";
+
+  imports = [ ./common.nix ];
+
+  nodes.machine = {
+    users.users.alice = { isNormalUser = true; };
+  };
+
+  testScript = ''
+    machine.wait_for_unit("multi-user.target")
+    machine.succeed("""
+      su --login --command "run-test-suite" alice >&2
+    """)
+  '';
+}
diff --git a/tests/nixos/functional/common.nix b/tests/nixos/functional/common.nix
new file mode 100644
index 000000000..493791a7b
--- /dev/null
+++ b/tests/nixos/functional/common.nix
@@ -0,0 +1,76 @@
+{ lib, ... }:
+
+let
+  # FIXME (roberth) reference issue
+  inputDerivation = pkg: (pkg.overrideAttrs (o: {
+    disallowedReferences = [ ];
+  })).inputDerivation;
+
+in
+{
+  imports = [
+    # Add the quickBuild attribute to the check package
+    ./quick-build.nix
+  ];
+
+  # We rarely change the script in a way that benefits from type checking, so
+  # we skip it to save time.
+  skipTypeCheck = true;
+
+  nodes.machine = { config, pkgs, ... }: {
+
+    virtualisation.writableStore = true;
+    system.extraDependencies = [
+      (inputDerivation config.nix.package)
+    ];
+
+    nix.settings.substituters = lib.mkForce [];
+
+    environment.systemPackages = let
+      run-test-suite = pkgs.writeShellApplication {
+        name = "run-test-suite";
+        runtimeInputs = [ pkgs.gnumake pkgs.jq pkgs.git ];
+        text = ''
+          set -x
+          cat /proc/sys/fs/file-max
+          ulimit -Hn
+          ulimit -Sn
+          cd ~
+          cp -r ${pkgs.nix.overrideAttrs (o: {
+            name = "nix-configured-source";
+            outputs = [ "out" ];
+            separateDebugInfo = false;
+            disallowedReferences = [ ];
+            buildPhase = ":";
+            checkPhase = ":";
+            installPhase = ''
+              cp -r . $out
+            '';
+            installCheckPhase = ":";
+            fixupPhase = ":";
+            doInstallCheck = true;
+          })} nix
+          chmod -R +w nix
+          cd nix
+
+          # Tests we don't need
+          echo >tests/functional/plugins/local.mk
+          sed -i tests/functional/local.mk \
+            -e 's!nix_tests += plugins\.sh!!' \
+            -e 's!nix_tests += test-libstoreconsumer\.sh!!' \
+            ;
+
+          export isTestOnNixOS=1
+          export version=${config.nix.package.version}
+          export NIX_REMOTE_=daemon
+          export NIX_REMOTE=daemon
+          export NIX_STORE=${builtins.storeDir}
+          make -j1 installcheck --keep-going
+        '';
+      };
+    in [
+      run-test-suite
+      pkgs.git
+    ];
+  };
+}
diff --git a/tests/nixos/functional/quick-build.nix b/tests/nixos/functional/quick-build.nix
new file mode 100644
index 000000000..10f4215e5
--- /dev/null
+++ b/tests/nixos/functional/quick-build.nix
@@ -0,0 +1,47 @@
+test@{ lib, extendModules, ... }:
+let
+  inherit (lib) mkOption types;
+in
+{
+  options = {
+    quickBuild = mkOption {
+      description = ''
+        Whether to perform a "quick" build of the Nix package to test.
+
+        When iterating on the functional tests, it's recommended to "set" this
+        to `true`, so that changes to the functional tests don't require any
+        recompilation of the package.
+        You can do so by buildin the `.quickBuild` attribute on the check package,
+        e.g:
+        ```console
+        nix build .#hydraJobs.functional_user.quickBuild
+        ```
+
+        We don't enable this by default to avoid the mostly unnecessary work of
+        performing an additional build of the package in cases where we build
+        the package normally anyway, such as in our pre-merge CI.
+      '';
+      type = types.bool;
+      default = false;
+    };
+  };
+
+  config = {
+    passthru.quickBuild = 
+      let withQuickBuild = extendModules { modules = [{ quickBuild = true; }]; };
+      in withQuickBuild.config.test;
+
+    defaults = { pkgs, ... }: {
+      config = lib.mkIf test.config.quickBuild {
+        nix.package = pkgs.nix_noTests;
+
+        system.forbiddenDependenciesRegexes = [
+          # This would indicate that the quickBuild feature is broken.
+          # It could happen if NixOS has a dependency on pkgs.nix instead of
+          # config.nix.package somewhere.
+          (builtins.unsafeDiscardStringContext pkgs.nix.outPath)
+        ];
+      };
+    };
+  };
+}
\ No newline at end of file