diff --git a/scripts/test/run_auto_unittests.py b/scripts/test/run_auto_unittests.py
index 831e900896..180e4e6919 100755
--- a/scripts/test/run_auto_unittests.py
+++ b/scripts/test/run_auto_unittests.py
@@ -52,12 +52,16 @@ def main():
                         dest='cwd',
                         help='Path to the directory containing the out dir',
                         default=devtools_paths.devtools_root_path())
+    parser.add_argument('--mocha-fgrep',
+                        dest='mocha_fgrep',
+                        help='Run only tests that match this string.')
     args = parser.parse_args(sys.argv[1:])
 
     efficiently_recompile.recompile(args.target, 'test/unittests')
     run_unittests.run_unit_tests_on_ninja_build_target(
         args.target, args.no_text_coverage, args.no_html_coverage,
-        args.coverage, args.expanded_reporting, args.chrome_binary, args.cwd)
+        args.coverage, args.expanded_reporting, args.chrome_binary, args.cwd,
+        args.mocha_fgrep)
 
 
 if __name__ == '__main__':
diff --git a/scripts/test/run_unittests.py b/scripts/test/run_unittests.py
index 4cbaaa8623..efb887c47b 100755
--- a/scripts/test/run_unittests.py
+++ b/scripts/test/run_unittests.py
@@ -23,7 +23,7 @@ import devtools_paths
 
 
 def run_tests(chrome_binary, target, no_text_coverage, no_html_coverage,
-              coverage, expanded_reporting, cwd):
+              coverage, expanded_reporting, cwd, mocha_fgrep):
     karmaconfig_path = os.path.join(cwd, 'out', target, 'gen', 'test',
                                     'unittests', 'karma.conf.js')
 
@@ -34,6 +34,7 @@ def run_tests(chrome_binary, target, no_text_coverage, no_html_coverage,
 
     print('Using karma config ' + karmaconfig_path)
 
+
     exec_command = [devtools_paths.node_path(), devtools_paths.karma_path(), 'start', test_helpers.to_platform_path_exact(karmaconfig_path)]
 
     env = os.environ.copy()
@@ -48,6 +49,9 @@ def run_tests(chrome_binary, target, no_text_coverage, no_html_coverage,
         env['EXPANDED_REPORTING'] = '1'
     if (chrome_binary is not None):
         env['CHROME_BIN'] = chrome_binary
+    if (mocha_fgrep is not None):
+        print('Using Mocha --fgrep flag ' + mocha_fgrep)
+        env['MOCHA_FGREP'] = mocha_fgrep
     exit_code = test_helpers.popen(exec_command, cwd=cwd, env=env)
     if exit_code == 1:
         return True
@@ -61,7 +65,8 @@ def run_unit_tests_on_ninja_build_target(target,
                                          coverage=False,
                                          expanded_reporting=False,
                                          chrome_binary=None,
-                                         cwd=None):
+                                         cwd=None,
+                                         mocha_fgrep=None):
     if chrome_binary and not test_helpers.check_chrome_binary(chrome_binary):
         print(
             'Chrome binary argument path does not exist or is not executable, reverting to downloaded binary'
@@ -88,7 +93,7 @@ def run_unit_tests_on_ninja_build_target(target,
 
     errors_found = run_tests(chrome_binary, target, no_text_coverage,
                              no_html_coverage, coverage, expanded_reporting,
-                             cwd)
+                             cwd, mocha_fgrep)
 
     if coverage and not no_html_coverage:
         print('')
@@ -137,12 +142,16 @@ def main():
                         dest='cwd',
                         help='Path to the directory containing the out dir',
                         default=devtools_paths.devtools_root_path())
+    parser.add_argument('--mocha-fgrep',
+                        dest='mocha_fgrep',
+                        help='Run only tests that match this string.')
     args = parser.parse_args(sys.argv[1:])
 
     run_unit_tests_on_ninja_build_target(args.target, args.no_text_coverage,
                                          args.no_html_coverage, args.coverage,
                                          args.expanded_reporting,
-                                         args.chrome_binary, args.cwd)
+                                         args.chrome_binary, args.cwd,
+                                         args.mocha_fgrep)
 
 
 if __name__ == '__main__':
diff --git a/test/unittests/karma.conf.js b/test/unittests/karma.conf.js
index 1ff66ec4df..b5c76f4960 100644
--- a/test/unittests/karma.conf.js
+++ b/test/unittests/karma.conf.js
@@ -20,6 +20,8 @@ const COVERAGE_ENABLED = Boolean(process.env['COVERAGE']) || Boolean(USER_DEFINE
 const EXPANDED_REPORTING = Boolean(process.env['EXPANDED_REPORTING']);
 const KARMA_TIMEOUT = process.env['KARMA_TIMEOUT'] ? Number(process.env['KARMA_TIMEOUT']) : undefined;
 
+const MOCHA_FGREP = process.env['MOCHA_FGREP'] || undefined;
+
 // true by default
 const TEXT_COVERAGE_ENABLED = COVERAGE_ENABLED && !process.env['NO_TEXT_COVERAGE'];
 // true by default
@@ -163,6 +165,10 @@ module.exports = function(config) {
        * so.
        */
       targetDir,
+
+      mocha: {
+        grep: MOCHA_FGREP,
+      }
     },
 
     plugins: [