diff --git a/src/calibre/debug.py b/src/calibre/debug.py
index 12cfec619c..dab247f3fc 100644
--- a/src/calibre/debug.py
+++ b/src/calibre/debug.py
@@ -103,7 +103,10 @@ Everything after the -- is passed to the script.
         'calibre-debug -r "Plugin name" -- file1 --option1\n'
         'Everything after the -- will be passed to the plugin as arguments.'))
     parser.add_option('-t', '--run-test', help=_(
-        'Run the named test(s)'))
+        'Run the named test(s). Use the special value "all" to run all tests.'
+        ' If the test name starts with a period it is assumed to be a module name.'
+        ' If the test name starts with @ it is assumed to be a category name.'
+    ))
     parser.add_option('--diff', action='store_true', default=False, help=_(
         'Run the calibre diff tool. For example:\n'
         'calibre-debug --diff file1 file2'))
diff --git a/src/calibre/utils/run_tests.py b/src/calibre/utils/run_tests.py
index 76f2b3eb43..508e38fe09 100644
--- a/src/calibre/utils/run_tests.py
+++ b/src/calibre/utils/run_tests.py
@@ -302,8 +302,17 @@ def find_tests(which_tests=None, exclude_tests=None):
 
 def run_test(test_name, verbosity=4, buffer=False):
     # calibre-debug -t test_name
-    tests = find_tests()
-    tests = filter_tests_by_name(tests, test_name)
+    which_tests = None
+    if test_name.startswith('@'):
+        which_tests = test_name[1:],
+    tests = find_tests(which_tests)
+    if test_name != 'all':
+        if test_name.startswith('.'):
+            tests = filter_tests_by_module(tests, test_name[1:])
+        elif test_name.startswith('@'):
+            pass
+        else:
+            tests = filter_tests_by_name(tests, test_name)
     if not tests._tests:
         raise SystemExit(f'No test named {test_name} found')
     run_cli(tests, verbosity, buffer=buffer)