diff --git a/flake.nix b/flake.nix
index ddc98c48a..0b6197512 100644
--- a/flake.nix
+++ b/flake.nix
@@ -84,6 +84,7 @@
           nix_2_18
           nix2container
           lixSrc
+          nixpkgs-regression
           ;
       };
 
@@ -96,7 +97,6 @@
         forAvailableSystems
         linux64BitSystems
         nixpkgsFor
-        nonDarwinSystems
         officialRelease
         overlayFor
         systems
@@ -105,6 +105,7 @@
 
       inherit (scope.callPackage ./nix-support/build/outputs.nix { })
         packages
+        tests
         ;
     in
     {
@@ -231,85 +232,7 @@
             doInstallCheck = false;
           });
 
-        # System tests.
-        tests =
-          import ./tests/nixos {
-            inherit
-              lib
-              nixpkgs
-              nixpkgsFor
-              ;
-          }
-          // {
-            # the n-e-j test suite is unusably slow in darwin ci. disbled until anywho fixes this.
-            nix-eval-jobs = (lib.genAttrs nonDarwinSystems) (
-              system: self.packages.${system}.nix-eval-jobs.tests.nix-eval-jobs
-            );
-
-            # This is x86_64-linux only, just because we have significantly
-            # cheaper x86_64-linux compute in CI.
-            # It is clangStdenv because clang's sanitizers are nicer.
-            asanBuild = self.packages.x86_64-linux.nix-clangStdenv.override {
-              # Improve caching of non-code changes by not changing the
-              # derivation name every single time, since this will never be seen
-              # by users anyway.
-              versionSuffix = "";
-              sanitize = [
-                "address"
-                "undefined"
-              ];
-              # it is very hard to make *every* CI build use this option such
-              # that we don't wind up building Lix twice, so we do it here where
-              # we are already doing so.
-              werror = true;
-            };
-
-            # Although this might be nicer to do with pre-commit, that would
-            # require adding 12MB of nodejs to the dev shell, whereas building it
-            # in CI with Nix avoids that at a cost of slower feedback on rarely
-            # touched files.
-            jsSyntaxCheck =
-              let
-                nixpkgs = nixpkgsFor.x86_64-linux.native;
-                inherit (nixpkgs) pkgs;
-                docSources = lib.fileset.toSource {
-                  root = ./doc;
-                  fileset = lib.fileset.fileFilter (f: f.hasExt "js") ./doc;
-                };
-              in
-              pkgs.runCommand "js-syntax-check" { } ''
-                find ${docSources} -type f -print -exec ${pkgs.nodejs-slim}/bin/node --check '{}' ';'
-                touch $out
-              '';
-
-            # clang-tidy run against the Lix codebase using the Lix clang-tidy plugin
-            clang-tidy = forAllSystems (
-              system:
-              let
-                pkgs = nixpkgsFor.${system}.native;
-              in
-              pkgs.callPackage ./package.nix {
-                # Required since we don't support gcc stdenv
-                stdenv = pkgs.clangStdenv;
-                versionSuffix = "";
-                lintInsteadOfBuild = true;
-              }
-            );
-
-            # Make sure that nix-env still produces the exact same result
-            # on a particular version of Nixpkgs.
-            evalNixpkgs = nixpkgsFor.x86_64-linux.native.callPackage ./tests/nixpkgs/eval.nix {
-              inherit nixpkgs-regression;
-            };
-
-            nixpkgsLibTests = forAllSystems (
-              system:
-              nixpkgsFor.${system}.native.callPackage ./tests/nixpkgs/lib.nix {
-                inherit nixpkgs system;
-                inherit (self.packages.${system}) nix;
-              }
-            );
-          };
+        inherit tests;
 
         pre-commit = forAvailableSystems (
           system:
diff --git a/nix-support/build/inputs.nix b/nix-support/build/inputs.nix
index 43c59a27d..ee8c13a86 100644
--- a/nix-support/build/inputs.nix
+++ b/nix-support/build/inputs.nix
@@ -4,6 +4,7 @@
   nixpkgs,
   nix_2_18,
   nix2container,
+  nixpkgs-regression,
 }:
 
 let
@@ -211,7 +212,7 @@ let
         });
       };
 
-    inherit nix2container nixpkgs;
+    inherit nix2container nixpkgs nixpkgs-regression;
   });
 in
 sc
diff --git a/nix-support/build/outputs.nix b/nix-support/build/outputs.nix
index 74adef1ca..e40f916bd 100644
--- a/nix-support/build/outputs.nix
+++ b/nix-support/build/outputs.nix
@@ -6,9 +6,12 @@
   stdenvs,
   lib,
   nix2container,
+  nixpkgs,
+  nonDarwinSystems,
+  nixpkgs-regression,
 }:
 
-{
+lib.fix (self: {
   packages = forAllSystems (
     system:
     rec {
@@ -48,4 +51,84 @@
       )
     )
   );
-}
+
+  # System tests.
+  tests =
+    import ../../tests/nixos {
+      inherit
+        lib
+        nixpkgs
+        nixpkgsFor
+        ;
+    }
+    // {
+      # the n-e-j test suite is unusably slow in darwin ci. disbled until anywho fixes this.
+      nix-eval-jobs = (lib.genAttrs nonDarwinSystems) (
+        system: self.packages.${system}.nix-eval-jobs.tests.nix-eval-jobs
+      );
+
+      # This is x86_64-linux only, just because we have significantly
+      # cheaper x86_64-linux compute in CI.
+      # It is clangStdenv because clang's sanitizers are nicer.
+      asanBuild = self.packages.x86_64-linux.nix-clangStdenv.override {
+        # Improve caching of non-code changes by not changing the
+        # derivation name every single time, since this will never be seen
+        # by users anyway.
+        versionSuffix = "";
+        sanitize = [
+          "address"
+          "undefined"
+        ];
+        # it is very hard to make *every* CI build use this option such
+        # that we don't wind up building Lix twice, so we do it here where
+        # we are already doing so.
+        werror = true;
+      };
+
+      # Although this might be nicer to do with pre-commit, that would
+      # require adding 12MB of nodejs to the dev shell, whereas building it
+      # in CI with Nix avoids that at a cost of slower feedback on rarely
+      # touched files.
+      jsSyntaxCheck =
+        let
+          nixpkgs = nixpkgsFor.x86_64-linux.native;
+          inherit (nixpkgs) pkgs;
+          docSources = lib.fileset.toSource {
+            root = ../../doc;
+            fileset = lib.fileset.fileFilter (f: f.hasExt "js") ../../doc;
+          };
+        in
+        pkgs.runCommand "js-syntax-check" { } ''
+          find ${docSources} -type f -print -exec ${pkgs.nodejs-slim}/bin/node --check '{}' ';'
+          touch $out
+        '';
+
+      # clang-tidy run against the Lix codebase using the Lix clang-tidy plugin
+      clang-tidy = forAllSystems (
+        system:
+        let
+          pkgs = nixpkgsFor.${system}.native;
+        in
+        pkgs.callPackage ../../package.nix {
+          # Required since we don't support gcc stdenv
+          stdenv = pkgs.clangStdenv;
+          versionSuffix = "";
+          lintInsteadOfBuild = true;
+        }
+      );
+
+      # Make sure that nix-env still produces the exact same result
+      # on a particular version of Nixpkgs.
+      evalNixpkgs = nixpkgsFor.x86_64-linux.native.callPackage ../../tests/nixpkgs/eval.nix {
+        inherit nixpkgs-regression;
+      };
+
+      nixpkgsLibTests = forAllSystems (
+        system:
+        nixpkgsFor.${system}.native.callPackage ../../tests/nixpkgs/lib.nix {
+          inherit nixpkgs system;
+          inherit (self.packages.${system}) nix;
+        }
+      );
+    };
+})