-output=$(notmuch insert $gen_msg_filename 2>&1)
-test_expect_equal "$output" "Error: tag '' in new.tags: empty tag forbidden"
+notmuch insert < $gen_msg_filename
+output=$(notmuch show --format=json id:$gen_msg_id)
+test_json_nodes <<<"$output" \
+ 'new_tags:[0][0][0]["tags"] = ["bar", "foo"]'
+
+test_begin_subtest "leading/trailing whitespace in new.tags is ignored"
+# avoid complications with leading spaces and "notmuch config"
+sed -i 's/^tags=.*$/tags= fu bar ; ; bar /' notmuch-config
+gen_insert_msg
+notmuch insert < $gen_msg_filename
+notmuch dump id:$gen_msg_id | sed 's/ --.*$//' > OUTPUT
+cat <<EOF >EXPECTED
+#notmuch-dump batch-tag:3 config,properties,tags
++bar +fu%20bar
+EOF
+test_expect_equal_file EXPECTED OUTPUT