add CI "all" target

ci.nix

@@ -70,4 +70,7 @@ let
           '';
       };
     };
-in  (genAttrs devices for-device) # tests # jobs
+in jobs //
+   {
+     all = pkgs.lib.collect pkgs.lib.isDerivation jobs;
+   }

doc/development.rst

@@ -232,18 +232,13 @@ Running tests
 *************
 
 You can run all of the tests by evaluating :file:`ci.nix`, which is the
-input I use in Hydra. Note that it expects Nixpkgs stable `and` unstable
-as inputs, because it builds the qemu device against both.
+input I use in Hydra. 
 
 .. code-block:: console
 
-    nix-build --argstr liminix `pwd`  --arg  nixpkgs "<nixpkgs>" \
-     --argstr unstable `pwd`/../unstable-nixpkgs/ ci.nix
-
-To run a single named test, use the ``-A`` flag. For example, ``-A pppoe``
-
-
-
+    nix-build -I liminix=`pwd`  ci.nix -A pppoe # run one job
+    nix-build -I liminix=`pwd`  ci.nix -A all # run all jobs
+    
 
 Troubleshooting
 ***************

tests/pseudofiles/test.nix

@@ -1,9 +1,9 @@
 let
   overlay = import <liminix/overlay.nix>;
-  nixpkgs = import <nixpkgs> { overlays = [overlay]; };
-  fixture = nixpkgs.callPackage ./fixture.nix {};
-in nixpkgs.runCommand "check" {
-    nativeBuildInputs = with <nixpkgs>; [ squashfsTools qprint ] ;
+  pkgs = import <nixpkgs> { overlays = [overlay]; };
+  fixture = pkgs.callPackage ./fixture.nix {};
+in pkgs.runCommand "check" {
+    nativeBuildInputs = with pkgs; [ squashfsTools qprint ] ;
   } ''
 set -e
 diff ${fixture} ${./result.expected}