Bug 1780076 - fix ordering of multiple setup tasks in xpcshell tests, r=nalexander

Differential Revision: https://phabricator.services.mozilla.com/D152119

testing/xpcshell/example/unit/test_multiple_setups.js

@@ -0,0 +1,13 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+let someVar = 0;
+
+add_setup(() => (someVar = 1));
+add_setup(() => (someVar = 2));
+
+add_task(async function test_setup_ordering() {
+  Assert.equal(someVar, 2, "Setups should have run in order.");
+});

testing/xpcshell/example/unit/test_multiple_tasks.js

@@ -0,0 +1,20 @@
+/* Any copyright is dedicated to the Public Domain.
+http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+let someVar = 0;
+
+add_task(async function test_first() {
+  Assert.equal(someVar, 1, "I should run as the first test task.");
+  someVar++;
+});
+
+add_setup(function setup() {
+  Assert.equal(someVar, 0, "Should run setup first.");
+  someVar++;
+});
+
+add_task(async function test_second() {
+  Assert.equal(someVar, 2, "I should run as the second test task.");
+});

testing/xpcshell/example/unit/xpcshell.ini

@@ -30,6 +30,8 @@ skip-if = os == "win" && debug
 [test_load.js]
 [test_load_httpd_js.js]
 [test_location.js]
+[test_multiple_setups.js]
+[test_multiple_tasks.js]
 [test_prefs_no_defaults.js]
 [test_prefs_no_defaults_with_file.js]
 prefs = dummy.pref.from.test.file=1

testing/xpcshell/head.js

@@ -1812,7 +1812,10 @@ function run_next_test() {
 
   function frontLoadSetups() {
     _gTests.sort(([propsA, funcA], [propsB, funcB]) => {
-      return propsB.isSetup ? 1 : 0;
+      if (propsB.isSetup === propsA.isSetup) {
+        return 0;
+      }
+      return propsB.isSetup ? 1 : -1;
     });
   }