diff --git a/src/tests/apinotify_handler.py b/src/tests/apinotify_handler.py
index f7674dad..4574d46a 100755
--- a/src/tests/apinotify_handler.py
+++ b/src/tests/apinotify_handler.py
@@ -1,7 +1,12 @@
 #!/usr/bin/env python
+"""
+Utility configured as apinotifypath in bitmessagesettings
+when pybitmessage started in test mode.
+"""
 
 import sys
 import tempfile
+
 from test_process import put_signal_file
 
 
diff --git a/src/tests/core.py b/src/tests/core.py
index 63589da9..3738c32e 100644
--- a/src/tests/core.py
+++ b/src/tests/core.py
@@ -1,3 +1,7 @@
+"""
+Tests for core.
+"""
+
 import unittest
 
 
@@ -8,5 +12,6 @@ class TestCore(unittest.TestCase):
 
 
 def run():
+    """Starts all tests defined in this module"""
     suite = unittest.TestLoader().loadTestsFromTestCase(TestCore)
     return unittest.TextTestRunner(verbosity=2).run(suite)
diff --git a/src/tests/test_api.py b/src/tests/test_api.py
index 942ad9bd..8915a735 100644
--- a/src/tests/test_api.py
+++ b/src/tests/test_api.py
@@ -1,12 +1,17 @@
-import xmlrpclib
+"""
+Tests using API.
+"""
+
 import base64
 import json
+import xmlrpclib
 from time import sleep
 
 from test_process import TestProcessProto
 
 
 class TestAPI(TestProcessProto):
+    """A test case for API"""
     _process_cmd = ['pybitmessage', '-t']
     _seed = base64.encodestring(
         'TIGER, tiger, burning bright. In the forests of the night'
@@ -14,11 +19,12 @@ class TestAPI(TestProcessProto):
 
     @classmethod
     def setUpClass(cls):
+        """Setup XMLRPC proxy for pybitmessage API"""
         super(TestAPI, cls).setUpClass()
         cls.addresses = []
         cls.api = xmlrpclib.ServerProxy(
             "http://username:password@127.0.0.1:8442/")
-        for tick in range(0, 5):
+        for _ in range(0, 5):
             if cls._get_readline('.api_started'):
                 print('API start detected!')
                 return
diff --git a/src/tests/test_process.py b/src/tests/test_process.py
index 06fc2998..45e0317e 100644
--- a/src/tests/test_process.py
+++ b/src/tests/test_process.py
@@ -1,19 +1,27 @@
-import unittest
-import subprocess
+"""
+Common reusable code for tests and tests for pybitmessage process.
+"""
+
 import os
 import signal
+import subprocess
 import tempfile
 import time
+import unittest
 
 import psutil
 
 
 def put_signal_file(path, filename):
+    """Creates file, presence of which is a signal about some event."""
     with open(os.path.join(path, filename), 'wb') as outfile:
         outfile.write(str(time.time()))
 
 
 class TestProcessProto(unittest.TestCase):
+    """Test case implementing common logic for external testing:
+    it starts pybitmessage in setUpClass() and stops it in tearDownClass()
+    """
     _process_cmd = ['pybitmessage', '-d']
     _threads_count = 14
     _files = (
@@ -23,6 +31,7 @@ class TestProcessProto(unittest.TestCase):
 
     @classmethod
     def setUpClass(cls):
+        """Setup environment and start pybitmessage"""
         cls.home = os.environ['BITMESSAGE_HOME'] = tempfile.gettempdir()
         put_signal_file(cls.home, 'unittest.lock')
         subprocess.call(cls._process_cmd)
@@ -48,6 +57,7 @@ class TestProcessProto(unittest.TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        """Ensures that pybitmessage stopped and removes files"""
         cls.process.send_signal(signal.SIGTERM)
         try:
             cls.process.wait(5)
@@ -80,6 +90,7 @@ class TestProcessProto(unittest.TestCase):
 
 
 class TestProcess(TestProcessProto):
+    """A test case for pybitmessage process"""
     def test_process_name(self):
         """Check PyBitmessage process name"""
         self.assertEqual(self.process.name(), 'PyBitmessage')