docker: add passthru.tests

pkgs/applications/virtualization/docker/default.nix

@@ -4,6 +4,7 @@
 , sqlite, iproute, lvm2, systemd
 , btrfs-progs, iptables, e2fsprogs, xz, utillinux, xfsprogs, git
 , procps, libseccomp
+, nixosTests
 }:
 
 with lib;
@@ -184,6 +185,8 @@ rec {
       installManPage man/*/*.[1-9]
     '';
 
+    passthru.tests = { inherit (nixosTests) docker; };
+
     meta = {
       homepage = "https://www.docker.com/";
       description = "An open source project to pack, ship and run any application as a lightweight container";