Re: [PATCH v7 6/6] refs: add GIT_REFERENCE_BACKEND to specify reference backend

diff --git a/t/t1423-ref-backend.sh b/t/t1423-ref-backend.sh
index 9912433b8c..d69aea3f7f 100755
--- a/t/t1423-ref-backend.sh
+++ b/t/t1423-ref-backend.sh

@@ -30,44 +39,86 @@ run_with_uri() {
 #   <repo> is the relative path to the repo to run the command in.
 #   <backend> is the original ref storage of the repo.
 #   <uri> is the new URI to be set for the ref storage.
+#   <via> if 'config', set the backend via the 'extensions.refStorage' config.
+#         if 'env', set the backend via the 'GIT_REFERENCE_BACKEND' env.
 #   <err_msg> (optional) if set, check if 'git-refs(1)' failed with the provided msg.
 test_refs_backend() {
 	repo=$1 &&
 	backend=$2 &&
 	uri=$3 &&
-	err_msg=$4 &&
+	via=$4 &&
+	err_msg=$5 &&
+
 
-	git -C "$repo" config set core.repositoryformatversion 1 &&
 	if test -n "$err_msg";
 	then
-		git -C "$repo" config set extensions.refStorage "$uri" &&
-		test_must_fail git -C "$repo" refs list 2>err &&
-		test_grep "$err_msg" err
+		if test "$via" = "env"
+		then
+			test_env GIT_REFERENCE_BACKEND="$uri" test_must_fail git -C "$repo" refs list 2>err
+		elif test "$via" = "config"
+		then
+			git -C "$repo" config set extensions.refStorage "$uri" &&
+			test_must_fail git -C "$repo" refs list 2>err &&
+			test_grep "$err_msg" err
+		fi
 	else
 		git -C "$repo" refs list >expect &&
-		run_with_uri "$repo" "$backend" "$uri" "refs list" >actual &&
+		run_with_uri "$repo" "$backend" "$uri" "refs list" "$via">actual &&
 		test_cmp expect actual
 	fi
 }
 
-test_expect_success 'URI is invalid' '
+# Verify that the expected files are present in the gitdir and the refsdir.
+# Usage: verify_files_exist <gitdir> <refdir>
+#   <gitdir> is the path for the gitdir.
+#   <refdir> is the path for the refdir.
+verify_files_exist() {
+	gitdir=$1 &&
+	refdir=$2 &&
+
+	# verify that the stubs were added to the $GITDIR.
+	cat $gitdir/refs/heads >actual &&
+	echo "repository uses alternate refs storage" >expect &&
+	test_cmp expect actual &&

+	cat $gitdir/HEAD >actual &&
+	echo "ref: refs/heads/.invalid" >expect &&
+	test_cmp expect actual