diff --git a/gallery_dl/extractor/2chan.py b/gallery_dl/extractor/2chan.py
index 8df8645b..33e79293 100644
--- a/gallery_dl/extractor/2chan.py
+++ b/gallery_dl/extractor/2chan.py
@@ -6,13 +6,13 @@
 # it under the terms of the GNU General Public License version 2 as
 # published by the Free Software Foundation.
 
-"""Extract images from https://www.2chan.net/"""
+"""Extractors for https://www.2chan.net/"""
 
 from .common import Extractor, Message
 from .. import text
 
 
-class FutabaThreadExtractor(Extractor):
+class _2chanThreadExtractor(Extractor):
     """Extractor for images from threads on www.2chan.net"""
     category = "2chan"
     subcategory = "thread"
diff --git a/gallery_dl/extractor/3dbooru.py b/gallery_dl/extractor/3dbooru.py
index 15f42076..febbb516 100644
--- a/gallery_dl/extractor/3dbooru.py
+++ b/gallery_dl/extractor/3dbooru.py
@@ -11,7 +11,7 @@
 from . import booru
 
 
-class ThreedeebooruExtractor(booru.MoebooruPageMixin, booru.BooruExtractor):
+class _3dbooruExtractor(booru.MoebooruPageMixin, booru.BooruExtractor):
     """Base class for 3dbooru extractors"""
     category = "3dbooru"
     api_url = "http://behoimi.org/post/index.json"
@@ -26,8 +26,7 @@ class ThreedeebooruExtractor(booru.MoebooruPageMixin, booru.BooruExtractor):
         })
 
 
-class ThreedeebooruTagExtractor(booru.TagMixin,
-                                ThreedeebooruExtractor):
+class _3dbooruTagExtractor(booru.TagMixin, _3dbooruExtractor):
     """Extractor for images from behoimi.org based on search-tags"""
     pattern = (r"(?:https?://)?(?:www\.)?behoimi\.org/post"
                r"(?:/(?:index)?)?\?tags=(?P<tags>[^&#]+)")
@@ -37,8 +36,7 @@ class ThreedeebooruTagExtractor(booru.TagMixin,
     })
 
 
-class ThreedeebooruPoolExtractor(booru.PoolMixin,
-                                 ThreedeebooruExtractor):
+class _3dbooruPoolExtractor(booru.PoolMixin, _3dbooruExtractor):
     """Extractor for image-pools from behoimi.org"""
     pattern = r"(?:https?://)?(?:www\.)?behoimi\.org/pool/show/(?P<pool>\d+)"
     test = ("http://behoimi.org/pool/show/27", {
@@ -47,8 +45,7 @@ class ThreedeebooruPoolExtractor(booru.PoolMixin,
     })
 
 
-class ThreedeebooruPostExtractor(booru.PostMixin,
-                                 ThreedeebooruExtractor):
+class _3dbooruPostExtractor(booru.PostMixin, _3dbooruExtractor):
     """Extractor for single images from behoimi.org"""
     pattern = r"(?:https?://)?(?:www\.)?behoimi\.org/post/show/(?P<post>\d+)"
     test = ("http://behoimi.org/post/show/140852", {
@@ -64,8 +61,7 @@ class ThreedeebooruPostExtractor(booru.PostMixin,
     })
 
 
-class ThreedeebooruPopularExtractor(booru.MoebooruPopularMixin,
-                                    ThreedeebooruExtractor):
+class _3dbooruPopularExtractor(booru.MoebooruPopularMixin, _3dbooruExtractor):
     """Extractor for popular images from behoimi.org"""
     pattern = (r"(?:https?://)?(?:www\.)?behoimi\.org"
                r"/post/popular_(?P<scale>by_(?:day|week|month)|recent)"
diff --git a/gallery_dl/extractor/foolfuuka.py b/gallery_dl/extractor/foolfuuka.py
index 5f4c5b8b..645b53a6 100644
--- a/gallery_dl/extractor/foolfuuka.py
+++ b/gallery_dl/extractor/foolfuuka.py
@@ -78,7 +78,7 @@ class FoolfuukaThreadExtractor(SharedConfigMixin, Extractor):
 
 EXTRACTORS = {
     "4plebs": {
-        "name": "fourplebs",
+        "name": "_4plebs",
         "root": "https://archive.4plebs.org",
         "pattern": r"(?:archive\.)?4plebs\.org",
         "test-thread": ("https://archive.4plebs.org/tg/thread/54059290", {
diff --git a/test/test_extractor.py b/test/test_extractor.py
index 6c09068f..2555b585 100644
--- a/test/test_extractor.py
+++ b/test/test_extractor.py
@@ -157,22 +157,12 @@ class TestExtractor(unittest.TestCase):
         def capitalize(c):
             if "-" in c:
                 return string.capwords(c.replace("-", " ")).replace(" ", "")
-            if "." in c:
-                c = c.replace(".", "")
             return c.capitalize()
 
-        mapping = {
-            "2chan"  : "futaba",
-            "3dbooru": "threedeebooru",
-            "4plebs" : "fourplebs",
-            "oauth"  : None,
-        }
-
         for extr in extractor.extractors():
-            category = mapping.get(extr.category, extr.category)
-            if category:
+            if extr.category not in ("", "oauth"):
                 expected = "{}{}Extractor".format(
-                    capitalize(category),
+                    capitalize(extr.category),
                     capitalize(extr.subcategory),
                 )
                 if expected[0].isdigit():