diff --git a/pkgs/build-support/testers/expect-failure.sh b/pkgs/build-support/testers/expect-failure.sh
index 052ee8527176..9c725d48bf34 100644
--- a/pkgs/build-support/testers/expect-failure.sh
+++ b/pkgs/build-support/testers/expect-failure.sh
@@ -34,6 +34,15 @@ echo "testBuildFailure: Original builder produced exit code: $r"
 
 # -----------------------------------------
 # Write the build log to the default output
+#
+# # from stdenv setup.sh
+getAllOutputNames() {
+    if [ -n "$__structuredAttrs" ]; then
+        echo "${!outputs[*]}"
+    else
+        echo "$outputs"
+    fi
+}
 
 outs=( $(getAllOutputNames) )
 defOut=${outs[0]}
diff --git a/pkgs/build-support/testers/test/default.nix b/pkgs/build-support/testers/test/default.nix
index 26e622c8763f..0a5381b2b738 100644
--- a/pkgs/build-support/testers/test/default.nix
+++ b/pkgs/build-support/testers/test/default.nix
@@ -58,9 +58,10 @@ lib.recurseIntoAttrs {
       inherit hello;
     } ''
       echo "Checking $failed/testBuildFailure.log"
-      grep -F 'testBuildFailure: The builder did not fail, but a failure was expected' $failed/testBuildFailure.log
+      grep -F 'testBuildFailure: The builder did not fail, but a failure was expected' $failed/testBuildFailure.log >/dev/null
       [[ 1 = $(cat $failed/testBuildFailure.exit) ]]
       touch $out
+      echo 'All good.'
     '';
 
     multiOutput = runCommand "testBuildFailure-multiOutput" {
diff --git a/pkgs/test/kernel.nix b/pkgs/test/kernel.nix
index a4da10030332..2ccd188b1edb 100644
--- a/pkgs/test/kernel.nix
+++ b/pkgs/test/kernel.nix
@@ -27,15 +27,9 @@ let
     { NIXOS_FAKE_MMC_BLOCK_MINORS = freeform "64"; } # will trigger an error but the message is not great:
   ];
 
-  yesWinsOverNoConfig = mkMerge [
-    # default for "NIXOS_TEST_BOOLEAN" is no
-    { "NIXOS_TEST_BOOLEAN"  = yes; } # yes wins over no by default
-    { "NIXOS_TEST_BOOLEAN"  = no; }
-  ];
-
-  optionalNoWins = mkMerge [
-    { NIXOS_FAKE_USB_DEBUG = option yes;}
-    { NIXOS_FAKE_USB_DEBUG = yes;}
+  mkDefaultWorksConfig = mkMerge [
+    { "NIXOS_TEST_BOOLEAN"  = yes; }
+    { "NIXOS_TEST_BOOLEAN"  = lib.mkDefault no; }
   ];
 
   allOptionalRemainOptional = mkMerge [
@@ -57,7 +51,7 @@ runTests {
   };
 
   testYesWinsOverNo = {
-    expr = (getConfig yesWinsOverNoConfig)."NIXOS_TEST_BOOLEAN".tristate;
+    expr = (getConfig mkDefaultWorksConfig)."NIXOS_TEST_BOOLEAN".tristate;
     expected = "y";
   };