From 7e3d2965a5ff0cce057bfca2e7f88d04a5f72192 Mon Sep 17 00:00:00 2001
From: Erik Arvstedt <erik.arvstedt@gmail.com>
Date: Wed, 11 Nov 2020 15:12:05 +0100
Subject: [PATCH] testing framework: re-add features removed in nixpkgs 20.09

Since nixpks 20.09, the test output is just an empty directory.
Restore saving the log output and linking to the driver.

Without linking to the driver, the driver is eligible for
garbage collection after running a test via `run-tests.sh --out-link-prefix`,
which implies lengthy driver rebuilds.
---
 test/lib/make-test-vm.nix | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/test/lib/make-test-vm.nix b/test/lib/make-test-vm.nix
index 26c85ad..c7eccdc 100644
--- a/test/lib/make-test-vm.nix
+++ b/test/lib/make-test-vm.nix
@@ -19,7 +19,19 @@ let
            '';
          };
        };
+       test' = test (args // { pkgs = pkgsFixed; });
     in
-      test (args // { pkgs = pkgsFixed; });
+      # See nixpkgs/nixos/lib/testing-python.nix for the original definition
+      test'.overrideAttrs (_: {
+        # 1. Save test output
+        # 2. Add link to driver so that a gcroot to a test prevents the driver from
+        #    being garbage-collected
+        buildCommand = ''
+          mkdir $out
+          LOGFILE=$out/output.xml tests='exec(os.environ["testScript"])' ${test'.driver}/bin/nixos-test-driver
+          ln -s ${test'.driver} $out/driver
+        '';
+      }) // { inherit (test') nodes driver; } ;
+
 in
   fixedTest