diff --git a/fretwork/midi/EventDispatcher.py b/fretwork/midi/EventDispatcher.py
index cd15fb9..50bb881 100644
--- a/fretwork/midi/EventDispatcher.py
+++ b/fretwork/midi/EventDispatcher.py
@@ -1,9 +1,8 @@
 # -*- coding: utf-8 -*-
 
-from DataTypeConverters import readBew
-from DataTypeConverters import toBytes
-
-from constants import *
+from .DataTypeConverters import readBew
+from .DataTypeConverters import toBytes
+from .constants import *
 
 
 class EventDispatcher:
diff --git a/fretwork/midi/MidiFileParser.py b/fretwork/midi/MidiFileParser.py
index e546aef..f5ce334 100644
--- a/fretwork/midi/MidiFileParser.py
+++ b/fretwork/midi/MidiFileParser.py
@@ -1,10 +1,8 @@
 # -*- coding: utf-8 -*-
 
-# uhh I don't really like this, but there are so many constants to
-# import otherwise
-from constants import *
+from .EventDispatcher import EventDispatcher
+from .constants import *
 
-from EventDispatcher import EventDispatcher
 
 class MidiFileParser(object):
 
@@ -41,7 +39,7 @@ def parseMThdChunk(self):
         header_chunk_zise = raw_in.readBew(4)
 
         # check if it is a proper midi file
-        if header_chunk_type != 'MThd':
+        if header_chunk_type != b'MThd':
             raise TypeError("It is not a valid midi file!")
 
         # Header values are at fixed locations, so no reason to be clever
diff --git a/fretwork/midi/MidiInFile.py b/fretwork/midi/MidiInFile.py
index ce48059..c5442b4 100644
--- a/fretwork/midi/MidiInFile.py
+++ b/fretwork/midi/MidiInFile.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 
-from RawInstreamFile import RawInstreamFile
-from MidiFileParser import MidiFileParser
+from .MidiFileParser import MidiFileParser
+from .RawInstreamFile import RawInstreamFile
 
 
 class MidiInFile(object):
@@ -38,14 +38,12 @@ def __init__(self, outStream, infile):
         self.raw_in = RawInstreamFile(infile)
         self.parser = MidiFileParser(self.raw_in, outStream)
 
-
     def read(self):
         "Start parsing the file"
         p = self.parser
         p.parseMThdChunk()
         p.parseMTrkChunks()
 
-
     def setData(self, data=''):
         "Sets the data from a plain string"
         self.raw_in.setData(data)
diff --git a/fretwork/midi/MidiInStream.py b/fretwork/midi/MidiInStream.py
index f9a6376..f3f5f44 100644
--- a/fretwork/midi/MidiInStream.py
+++ b/fretwork/midi/MidiInStream.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 
-from MidiOutStream import MidiOutStream
+from .MidiOutStream import MidiOutStream
+
 
 class MidiInStream(object):
 
diff --git a/fretwork/midi/MidiOutFile.py b/fretwork/midi/MidiOutFile.py
index 51db2bb..29fc139 100644
--- a/fretwork/midi/MidiOutFile.py
+++ b/fretwork/midi/MidiOutFile.py
@@ -1,10 +1,11 @@
 # -*- coding: utf-8 -*-
 
-from MidiOutStream import MidiOutStream
-from RawOutstreamFile import RawOutstreamFile
+from .DataTypeConverters import fromBytes
+from .DataTypeConverters import writeVar
+from .MidiOutStream import MidiOutStream
+from .RawOutstreamFile import RawOutstreamFile
+from .constants import *
 
-from constants import *
-from DataTypeConverters import fromBytes, writeVar
 
 class MidiOutFile(MidiOutStream):
 
diff --git a/fretwork/midi/MidiToText.py b/fretwork/midi/MidiToText.py
index 0fa19d3..23d9441 100644
--- a/fretwork/midi/MidiToText.py
+++ b/fretwork/midi/MidiToText.py
@@ -1,7 +1,9 @@
 #!/usr/bin/python
 # -*- coding: utf-8 -*-
 
-from MidiOutStream import MidiOutStream
+from .MidiOutStream import MidiOutStream
+
+
 class MidiToText(MidiOutStream):
 
 
diff --git a/fretwork/midi/RawInstreamFile.py b/fretwork/midi/RawInstreamFile.py
index 260d4a3..d1aa030 100644
--- a/fretwork/midi/RawInstreamFile.py
+++ b/fretwork/midi/RawInstreamFile.py
@@ -3,9 +3,9 @@
 
 import os.path
 
-from DataTypeConverters import readBew as readBew_
-from DataTypeConverters import readVar
-from DataTypeConverters import varLen
+from .DataTypeConverters import readBew as readBew_
+from .DataTypeConverters import readVar
+from .DataTypeConverters import varLen
 
 
 class RawInstreamFile(object):
diff --git a/fretwork/midi/RawOutstreamFile.py b/fretwork/midi/RawOutstreamFile.py
index cfd8af8..c28fc0d 100644
--- a/fretwork/midi/RawOutstreamFile.py
+++ b/fretwork/midi/RawOutstreamFile.py
@@ -1,12 +1,16 @@
 # -*- coding: utf-8 -*-
 
-# standard library imports
 import sys
-from types import StringType
-from cStringIO import StringIO
+try:
+    from cStringIO import StringIO
+    from types import StringType
+except ImportError:
+    import io as StringIO
+    StringType = str
+
+from .DataTypeConverters import writeVar
+from .DataTypeConverters import writeBew
 
-# custom import
-from DataTypeConverters import writeBew, writeVar
 
 class RawOutstreamFile(object):
 
diff --git a/fretwork/midi/__init__.py b/fretwork/midi/__init__.py
index fd71283..362ca9b 100644
--- a/fretwork/midi/__init__.py
+++ b/fretwork/midi/__init__.py
@@ -1,10 +1,10 @@
 # -*- coding: utf-8 -*-
 
-from MidiOutStream import MidiOutStream
-from MidiOutFile import MidiOutFile
-from MidiInStream import MidiInStream
-from MidiInFile import MidiInFile
-from MidiToText import MidiToText
+from .MidiInFile import MidiInFile
+from .MidiInStream import MidiInStream
+from .MidiOutFile import MidiOutFile
+from .MidiOutStream import MidiOutStream
+from .MidiToText import MidiToText
 
 __all__ = ['MidiOutStream',
            'MidiOutFile',
diff --git a/tests/midi/__init__.py b/tests/midi/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/midi/drumtest_notes.mid b/tests/midi/drumtest_notes.mid
new file mode 100644
index 0000000..a7da58d
Binary files /dev/null and b/tests/midi/drumtest_notes.mid differ
diff --git a/tests/midi/test_datatypeconverters.py b/tests/midi/test_datatypeconverters.py
new file mode 100644
index 0000000..16ded2b
--- /dev/null
+++ b/tests/midi/test_datatypeconverters.py
@@ -0,0 +1,63 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+# FoFiX
+# Copyright (C) 2017 FoFiX team
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+import sys
+import unittest
+
+from fretwork.midi.DataTypeConverters import readBew
+from fretwork.midi.DataTypeConverters import readVar
+from fretwork.midi.DataTypeConverters import toBytes
+from fretwork.midi.DataTypeConverters import varLen
+
+
+class DataTypeConvertersTest(unittest.TestCase):
+
+    def test_toBytes_type(self):
+        if sys.version_info.major == 2:
+            value = bytes('áâãa')
+        else:
+            value = bytes('áâãa', 'utf-8')
+        result = toBytes(value)
+        self.assertIs(type(result), tuple)
+
+    def test_readBew_keyerror(self):
+        if sys.version_info.major == 2:
+            value = bytes('aà')
+        else:
+            value = bytes('aà', 'utf-8')
+        self.assertIs(readBew(value), 0)
+
+    def test_readBew_type(self):
+        value = b'a'
+        result = readBew(value)
+        self.assertIs(type(result), int)
+
+    def test_readVar(self):
+        if sys.version_info.major == 2:
+            value = bytes('áâãa')
+        else:
+            value = bytes('áâãa', 'utf-8')
+        self.assertEqual(readVar(value), 295821045191137)
+
+    def test_varLen(self):
+        self.assertEqual(varLen(97), 1)
+        self.assertEqual(varLen(256), 2)
+        self.assertEqual(varLen(20000), 3)
+        self.assertEqual(varLen(2107151), 4)
diff --git a/tests/midi/test_midiinfile.py b/tests/midi/test_midiinfile.py
new file mode 100644
index 0000000..2472fd4
--- /dev/null
+++ b/tests/midi/test_midiinfile.py
@@ -0,0 +1,37 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+# FoFiX
+# Copyright (C) 2017 FoFiX team
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+import unittest
+
+from fretwork.midi.MidiInFile import MidiInFile
+from fretwork.midi.MidiToText import MidiToText
+
+
+class MidiInFileTest(unittest.TestCase):
+
+    def setUp(self):
+        self.test_file = "tests/midi/drumtest_notes.mid"
+
+    def test_init(self):
+        MidiInFile(MidiToText(), self.test_file)
+
+    def test_read(self):
+        midi_in = MidiInFile(MidiToText(), self.test_file)
+        midi_in.read()