--- a/browser/components/enterprisepolicies/tests/browser/browser.ini
+++ b/browser/components/enterprisepolicies/tests/browser/browser.ini
@@ -1,17 +1,14 @@
 [DEFAULT]
 prefs =
   browser.policies.enabled=true
 support-files =
   head.js
-  config_dont_check_default_browser.json
   config_popups_cookies_addons_flash.json
-  config_setAndLockPref.json
-  config_simple_policies.json
   config_broken_json.json
   config_block_about_config.json
 
 [browser_policies_broken_json.js]
 [browser_policies_popups_cookies_addons_flash.js]
 [browser_policies_setAndLockPref_API.js]
 [browser_policies_simple_policies.js]
 [browser_policies_validate_and_parse_API.js]

--- a/browser/components/enterprisepolicies/tests/browser/browser_policies_setAndLockPref_API.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policies_setAndLockPref_API.js
@@ -90,18 +90,26 @@ add_task(async function test_API_through
 
   Policies.string_policy = {
     onBeforeUIStartup(manager, param) {
       setAndLockPref("policies.test2.stringPref", param);
     }
   };
 
   await setupPolicyEngineWithJson(
-    "config_setAndLockPref.json",
-    /* custom schema */
+    // policies.json
+    {
+      "policies": {
+        "bool_policy": true,
+        "int_policy": 42,
+        "string_policy": "policies test 2"
+      }
+    },
+
+    // custom schema
     {
       properties: {
         "bool_policy": {
           "type": "boolean"
         },
 
         "int_policy": {
           "type": "integer"

--- a/browser/components/enterprisepolicies/tests/browser/browser_policies_simple_policies.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policies_simple_policies.js
@@ -47,18 +47,27 @@ add_task(async function test_simple_poli
   Policies.simple_policy3 = {
     onAllWindowsRestored(manager, param) {
       is(param, false, "Param matches what was passed in config file");
       policy3Ran = true;
     }
   };
 
   await setupPolicyEngineWithJson(
-    "config_simple_policies.json",
-    /* custom schema */
+    // policies.json
+    {
+      "policies": {
+        "simple_policy0": true,
+        "simple_policy1": true,
+        "simple_policy2": true,
+        "simple_policy3": false
+      }
+    },
+
+    // custom schema
     {
       properties: {
         "simple_policy0": {
           "type": "boolean"
         },
 
         "simple_policy1": {
           "type": "boolean"

--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_default_browser_check.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_default_browser_check.js
@@ -8,17 +8,21 @@ const { ShellService } = Cu.import("reso
 add_task(async function test_default_browser_check() {
   ShellService._checkedThisSession = false;
   // On a normal profile, the default is true. However, this gets set to false on the
   // testing profile. Let's start with true for a sanity check.
 
   ShellService.shouldCheckDefaultBrowser = true;
   is(ShellService.shouldCheckDefaultBrowser, true, "Sanity check");
 
-  await setupPolicyEngineWithJson("config_dont_check_default_browser.json");
+  await setupPolicyEngineWithJson({
+    "policies": {
+      "dont_check_default_browser": true
+    }
+  });
 
   is(ShellService.shouldCheckDefaultBrowser, false, "Policy changed it to not check");
 
   // Try to change it to true and check that it doesn't take effect
   ShellService.shouldCheckDefaultBrowser = true;
 
   is(ShellService.shouldCheckDefaultBrowser, false, "Policy is enforced");
 

deleted file mode 100644
--- a/browser/components/enterprisepolicies/tests/browser/config_dont_check_default_browser.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "policies": {
-    "dont_check_default_browser": true
-  }
-}

deleted file mode 100644
--- a/browser/components/enterprisepolicies/tests/browser/config_setAndLockPref.json
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-  "policies": {
-    "bool_policy": true,
-    "int_policy": 42,
-    "string_policy": "policies test 2"
-  }
-}

deleted file mode 100644
--- a/browser/components/enterprisepolicies/tests/browser/config_simple_policies.json
+++ /dev/null
@@ -1,8 +0,0 @@
-{
-  "policies": {
-    "simple_policy0": true,
-    "simple_policy1": true,
-    "simple_policy2": true,
-    "simple_policy3": false
-  }
-}

--- a/browser/components/enterprisepolicies/tests/browser/head.js
+++ b/browser/components/enterprisepolicies/tests/browser/head.js
@@ -1,16 +1,31 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
-async function setupPolicyEngineWithJson(jsonName, customSchema) {
-  let filePath = getTestFilePath(jsonName ? jsonName : "non-existing-file.json");
+XPCOMUtils.defineLazyModuleGetter(this, "FileTestUtils",
+                                  "resource://testing-common/FileTestUtils.jsm");
+
+async function setupPolicyEngineWithJson(json, customSchema) {
+  let filePath;
+  if (typeof(json) == "object") {
+    filePath = FileTestUtils.getTempFile("policies.json").path;
+
+    // This file gets automatically deleted by FileTestUtils
+    // at the end of the test run.
+    await OS.File.writeAtomic(filePath, JSON.stringify(json), {
+      encoding: "utf-8",
+    });
+  } else {
+    filePath = getTestFilePath(json ? json : "non-existing-file.json");
+  }
+
   Services.prefs.setStringPref("browser.policies.alternatePath", filePath);
 
   let resolve = null;
   let promise = new Promise((r) => resolve = r);
 
   Services.obs.addObserver(function observer() {
     Services.obs.removeObserver(observer, "EnterprisePolicies:AllPoliciesApplied");
     resolve();