tests: use callTest pattern

Allows using the `callPackage(s)` pattern on tests.

Rather than using `pkgs.callPackage`, we implement our own variant using
`lib.callPackageWith`.

Our variant (`callTest`) includes additional nixvim-specific stuff
commonly used by our tests.

tests/default.nix

@@ -7,47 +7,43 @@
   self, # The flake instance
 }:
 let
+  autoArgs = pkgs // {
+    inherit
+      helpers
+      lib
+      pkgsUnfree
+      self
+      system
+      ;
     inherit (self.legacyPackages.${system})
       makeNixvimWithModule
       nixvimConfiguration
       ;
+    inherit (self.lib.${system}.check)
+      mkTestDerivationFromNvim
+      mkTestDerivationFromNixvimModule
+      ;
+    # Recursive:
+    inherit callTest callTests;
+  };
+
+  callTest = lib.callPackageWith autoArgs;
+  callTests = lib.callPackagesWith autoArgs;
 in
 {
-  extra-args-tests = import ./extra-args.nix {
-    inherit pkgs;
-    inherit makeNixvimWithModule;
-  };
-  extend = import ./extend.nix { inherit pkgs makeNixvimWithModule; };
-  extra-files = import ./extra-files.nix { inherit pkgs makeNixvimWithModule; };
-  enable-except-in-tests = import ./enable-except-in-tests.nix {
-    inherit pkgs makeNixvimWithModule;
-    inherit (self.lib.${system}.check) mkTestDerivationFromNixvimModule;
-  };
-  failing-tests = pkgs.callPackage ./failing-tests.nix {
-    inherit (self.lib.${system}.check) mkTestDerivationFromNixvimModule;
-  };
-  no-flake = import ./no-flake.nix {
-    inherit system;
-    inherit (self.lib.${system}.check) mkTestDerivationFromNvim;
-    nixvim = "${self}";
-  };
-  lib-tests = import ./lib-tests.nix {
-    inherit pkgs helpers;
-    inherit (pkgs) lib;
-  };
-  maintainers = import ./maintainers.nix { inherit pkgs; };
-  plugins-by-name = pkgs.callPackage ./plugins-by-name.nix { inherit nixvimConfiguration; };
-  generated = pkgs.callPackage ./generated.nix { };
-  package-options = pkgs.callPackage ./package-options.nix { inherit nixvimConfiguration; };
-  lsp-all-servers = pkgs.callPackage ./lsp-servers.nix { inherit nixvimConfiguration; };
+  extra-args-tests = callTest ./extra-args.nix { };
+  extend = callTest ./extend.nix { };
+  extra-files = callTest ./extra-files.nix { };
+  enable-except-in-tests = callTest ./enable-except-in-tests.nix { };
+  failing-tests = callTest ./failing-tests.nix { };
+  no-flake = callTest ./no-flake.nix { };
+  lib-tests = callTest ./lib-tests.nix { };
+  maintainers = callTest ./maintainers.nix { };
+  plugins-by-name = callTest ./plugins-by-name.nix { };
+  generated = callTest ./generated.nix { };
+  package-options = callTest ./package-options.nix { };
+  lsp-all-servers = callTest ./lsp-servers.nix { };
 }
 # Tests generated from ./test-sources
 # Grouped as a number of link-farms in the form { test-1, test-2, ... test-N }
-// import ./main.nix {
-  inherit
-    lib
-    pkgs
-    pkgsUnfree
-    helpers
-    ;
-}
+// callTests ./main.nix { }

tests/main.nix

@@ -1,13 +1,15 @@
 # Collects the various test modules in tests/test-sources/ and groups them into a number of test derivations
 {
-  lib ? pkgs.lib,
+  callPackage,
+  callTest,
   helpers,
+  lib ? pkgs.lib,
   pkgs,
   pkgsUnfree,
 }:
 let
-  fetchTests = import ./fetch-tests.nix { inherit lib pkgs helpers; };
-  test-derivation = import ../lib/tests.nix { inherit pkgs lib; };
+  fetchTests = callTest ./fetch-tests.nix { };
+  test-derivation = callPackage ../lib/tests.nix { };
   inherit (test-derivation) mkTestDerivationFromNixvimModule;
 
   moduleToTest =

tests/no-flake.nix

@@ -1,6 +1,7 @@
 {
+  nixvim ? "${self}",
+  self ? throw "either supply `self` or `nixvim`",
   system,
-  nixvim,
   mkTestDerivationFromNvim,
 }:
 let