--- a/dom/plugins/test/unit/test_nice_plugin_name.js
+++ b/dom/plugins/test/unit/test_nice_plugin_name.js
@@ -84,17 +84,18 @@ function run_test() {
   test_expected_permission_string(expectedDefaultPermissionString);
 
   let suffix = get_platform_specific_plugin_suffix();
   let pluginFile = get_test_plugin_no_symlink();
   let pluginDir = pluginFile.parent;
   pluginFile.copyTo(null, "npblah235" + suffix);
   let pluginCopy = pluginDir.clone();
   pluginCopy.append("npblah235" + suffix);
-  pluginFile.moveTo(pluginDir.parent, null);
+  let tempDir = do_get_tempdir();
+  pluginFile.moveTo(tempDir, null);
   test_expected_permission_string("plugin:npblah");
 
   pluginCopy.moveTo(null, "npasdf-3.2.2" + suffix);
   test_expected_permission_string("plugin:npasdf");
 
   pluginCopy.moveTo(null, "npasdf_##29387!{}{[][" + suffix);
   test_expected_permission_string("plugin:npasdf");
 

--- a/dom/plugins/test/unit/test_persist_in_prefs.js
+++ b/dom/plugins/test/unit/test_persist_in_prefs.js
@@ -45,17 +45,17 @@ function write_registry(version, info) {
 function run_test() {
   do_check_true(gIsWindows || gIsOSX || gIsLinux);
 
   let file = get_test_plugin_no_symlink();
   if (!file)
     do_throw("Plugin library not found");
 
   const pluginDir = file.parent;
-  const parentDir = pluginDir.parent;
+  const tempDir = do_get_tempdir();
   const suffix = get_platform_specific_plugin_suffix();
   const pluginName = file.leafName.substring(0, file.leafName.length - suffix.length).toLowerCase();
   const pluginHost = Cc["@mozilla.org/plugin/host;1"].getService(Ci.nsIPluginHost);
   const statePref = "plugin.state." + pluginName;
 
   // write plugin registry data
   let registry = "";
 
@@ -85,17 +85,17 @@ function run_test() {
   do_check_false(plugin.clicktoplay);
   // ... and imported into prefs, with 0 being the disabled state
   do_check_eq(0, Services.prefs.getIntPref(statePref));
 
   // prepare a copy of the plugin and backup the original
   file.copyTo(null, "nptestcopy" + suffix);
   let copy = pluginDir.clone();
   copy.append("nptestcopy" + suffix);
-  file.moveTo(parentDir, null);
+  file.moveTo(tempDir, null);
 
   // test that the settings persist through a few variations of test-plugin names
   let testNames = [
     pluginName + "2",
     pluginName.toUpperCase() + "_11_5_42_2323",
     pluginName + "-5.2.7"
   ];
   testNames.forEach(function(leafName) {
@@ -104,17 +104,17 @@ function run_test() {
     pluginHost.reloadPlugins(false);
     plugin = get_test_plugintag();
     do_check_false(plugin == null);
     do_check_true(plugin.disabled);
     do_check_false(plugin.clicktoplay);
   });
 
   // check that the state persists even if the plugin is not always present
-  copy.moveTo(parentDir, null);
+  copy.moveTo(tempDir, null);
   pluginHost.reloadPlugins(false);
   copy.moveTo(pluginDir, null);
   pluginHost.reloadPlugins(false);
 
   plugin = get_test_plugintag();
   do_check_false(plugin == null);
   do_check_true(plugin.disabled);
   do_check_false(plugin.clicktoplay);