--- a/testing/firefox-ui/mach_commands.py
+++ b/testing/firefox-ui/mach_commands.py
@@ -32,17 +32,18 @@ def run_firefox_ui_test(testtype=None, t
     import argparse
 
     from mozlog.structured import commandline
     import firefox_ui_harness
 
     test_types = {
         'functional': {
             'default_tests': [
-                'manifest.ini',
+                os.path.join('puppeteer', 'manifest.ini'),
+                os.path.join('functional', 'manifest.ini'),
             ],
             'cli_module': firefox_ui_harness.cli_functional,
         },
         'update': {
             'default_tests': [
                 os.path.join('update', 'manifest.ini'),
             ],
             'cli_module': firefox_ui_harness.cli_update,

deleted file mode 100644
--- a/testing/firefox-ui/tests/manifest.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[include:puppeteer/manifest.ini]
-[include:functional/manifest.ini]

--- a/testing/mozharness/mozharness/mozilla/testing/firefox_ui_tests.py
+++ b/testing/mozharness/mozharness/mozilla/testing/firefox_ui_tests.py
@@ -328,18 +328,19 @@ class FirefoxUITests(TestingMixin, VCSTo
 
         if self.query_minidump_stackwalk():
             env['MINIDUMP_STACKWALK'] = self.minidump_stackwalk_path
 
         parser = StructuredOutputParser(config=self.config,
                                         log_obj=self.log_obj,
                                         strict=False)
 
-        # Add the top-level tests manifest file
-        cmd.append(os.path.join(dirs['abs_fxui_dir'], 'tests', self.tests_manifest))
+        # Add the default tests to run
+        tests = [os.path.join(dirs['abs_fxui_dir'], 'tests', test) for test in self.default_tests]
+        cmd.extend(tests)
 
         return_code = self.run_command(cmd,
                                        cwd=dirs['abs_work_dir'],
                                        output_timeout=300,
                                        output_parser=parser,
                                        env=env)
 
         tbpl_status, log_level = parser.evaluate_parser(return_code)
@@ -406,23 +407,28 @@ class FirefoxUITests(TestingMixin, VCSTo
         except zipfile.BadZipfile as e:
             self.log('%s (%s)' % (e.message, zip),
                      level=FATAL, exit_code=2)
 
 
 class FirefoxUIFunctionalTests(FirefoxUITests):
 
     cli_script = 'cli_functional.py'
-    tests_manifest = 'manifest.ini'
+    default_tests = [
+        os.path.join('puppeteer', 'manifest.ini'),
+        os.path.join('functional', 'manifest.ini'),
+    ]
 
 
 class FirefoxUIUpdateTests(FirefoxUITests):
 
     cli_script = 'cli_update.py'
-    tests_manifest = os.path.join('update', 'manifest.ini')
+    default_tests = [
+        os.path.join('update', 'manifest.ini')
+    ]
 
     def __init__(self, config_options=None, *args, **kwargs):
         config_options = config_options or firefox_ui_update_config_options
 
         super(FirefoxUIUpdateTests, self).__init__(
             config_options=config_options,
             *args, **kwargs
         )