diff --git a/.gitignore b/.gitignore
index 090eda8..3c5e847 100644
--- a/.gitignore
+++ b/.gitignore
@@ -59,3 +59,4 @@ target/
 
 # Virtualenv
 env/
+.python-version
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..21f9f3a
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,5 @@
+language: python
+python:
+  - "3.6"
+script:
+  - python tests.py
\ No newline at end of file
diff --git a/README.md b/README.md
index 5787d32..b678ac5 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
 # sms-counter-python
 ----
+[![Build Status](https://travis-ci.com/uralov/sms-counter-python.svg?branch=master)](https://travis-ci.com/uralov/sms-counter-python)
 
 **sms-counter-python** is a lib that help to count characters of SMS messages.
 
diff --git a/sms_counter/main.py b/sms_counter/main.py
index 257aa85..90950cd 100644
--- a/sms_counter/main.py
+++ b/sms_counter/main.py
@@ -1,8 +1,8 @@
 # -*- coding: utf8 -*-
-'''
+"""
 Created on Jul 10, 2016
 @author: Dayo
-'''
+"""
 from math import ceil
 
 
@@ -45,17 +45,15 @@ class SMSCounter(object):
     def _detect_encoding(cls, plaintext):
         rf = cls._text_to_unicode_pointcode_list(plaintext)
 
-        utf16chars = set(rf).difference(set(cls._get_gsm_7bit_map()))
+        non_gsm_7bit_chars = set(rf) - set(cls._get_gsm_7bit_map())
+        if not non_gsm_7bit_chars:
+            return cls.GSM_7BIT
 
-        if len(utf16chars):
-            return cls.UTF16
-
-        exchars = set(rf).intersection(set(cls._get_added_gsm_7bit_ex_map()))
-
-        if len(exchars):
+        non_gsm_7bit_ex_chars = non_gsm_7bit_chars - set(cls._get_added_gsm_7bit_ex_map())
+        if not non_gsm_7bit_ex_chars:
             return cls.GSM_7BIT_EX
 
-        return cls.GSM_7BIT
+        return cls.UTF16
 
     @classmethod
     def count(cls, plaintext):
diff --git a/tests.py b/tests.py
new file mode 100644
index 0000000..4424414
--- /dev/null
+++ b/tests.py
@@ -0,0 +1,58 @@
+from unittest import TestCase
+
+from sms_counter import SMSCounter
+
+
+class SMSCounterTestCase(TestCase):
+    """ Tests for sms counting """
+    GSM_7BIT_LEN = 160
+    GSM_7BIT_LEN_MULTIPART = 153
+    UTF16_LEN = 70
+    UTF16_LEN_MULTIPART = 67
+    GSM_7BIT_CHAR_MAP = list(map(chr, SMSCounter._get_gsm_7bit_map()))
+    GSM_7BIT_EX_CHAR_MAP = list(map(chr, SMSCounter._get_added_gsm_7bit_ex_map()))
+
+    def _check_gsm_7bit_sms_length(self, counter, message, message_max_length=GSM_7BIT_LEN):
+        length_error = 'Message length should be less than {} symbols'.format(message_max_length)
+        self.assertLessEqual(len(message), counter.get('per_message'), length_error)
+        self.assertEqual(len(message), counter.get('length'))
+        self.assertEqual(counter.get('messages'), 1, 'Message is not multipart')
+
+    def test_gsm_7bit_chars(self):
+        message = self.GSM_7BIT_CHAR_MAP[:self.GSM_7BIT_LEN]
+        counter = SMSCounter.count(message)
+        self._check_gsm_7bit_sms_length(counter, message)
+        self.assertEqual(counter.get('encoding'), SMSCounter.GSM_7BIT)
+
+    def test_gsm_7bit_ex_chars(self):
+        message = self.GSM_7BIT_CHAR_MAP + self.GSM_7BIT_EX_CHAR_MAP
+        message = message[:self.GSM_7BIT_LEN]
+        counter = SMSCounter.count(message)
+        self._check_gsm_7bit_sms_length(counter, message)
+        self.assertEqual(counter.get('encoding'), SMSCounter.GSM_7BIT_EX)
+
+    def test_utf_chars(self):
+        utf_message = ['£', 'ф', '±'] + self.GSM_7BIT_CHAR_MAP
+        utf_message = utf_message[:self.UTF16_LEN]
+        counter = SMSCounter.count(utf_message)
+        self._check_gsm_7bit_sms_length(counter, utf_message, self.UTF16_LEN)
+        self.assertEqual(counter.get('encoding'), SMSCounter.UTF16)
+
+    def test_multipart_sms_gsm_7bit(self):
+        message = self.GSM_7BIT_CHAR_MAP + self.GSM_7BIT_EX_CHAR_MAP
+        double_message = message[:self.GSM_7BIT_LEN_MULTIPART] * 2
+        counter = SMSCounter.count(double_message)
+        self.assertEqual(counter.get('encoding'), SMSCounter.GSM_7BIT_EX)
+        self.assertEqual(counter.get('messages'), 2, 'Message must contains from 2 parts')
+
+    def test_multipart_sms_utf(self):
+        utf_message = ['£', 'ф', '±'] + self.GSM_7BIT_CHAR_MAP
+        double_utf_message = utf_message[:self.UTF16_LEN_MULTIPART] * 2
+        counter = SMSCounter.count(double_utf_message)
+        self.assertEqual(counter.get('encoding'), SMSCounter.UTF16)
+        self.assertEqual(counter.get('messages'), 2, 'Message must contains from 2 parts')
+
+
+if __name__ == '__main__':
+    import unittest
+    unittest.main()