diff --git a/.gitignore b/.gitignore
index ba04aac..b8fd992 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,4 +6,6 @@
 /xmodem.egg-info
 /.coverage
 /.tox
+/.cache
+/.idea
 *.py.swp
diff --git a/test/unit/test_xmodem.py b/test/unit/test_xmodem.py
index 3b724d5..0e0c96c 100644
--- a/test/unit/test_xmodem.py
+++ b/test/unit/test_xmodem.py
@@ -10,7 +10,8 @@
     import StringIO.StringIO as BytesIO
 
 # local
-import xmodem
+from xmodem import XMODEM
+from xmodem import NAK, CRC, ACK
 
 # 3rd-party
 import pytest
@@ -24,24 +25,122 @@ def dummy_putc(data, timeout=1):
     return 0
 
 
+def test_xmodem_bad_mode():
+    # given,
+    mode = 'XXX'
+    modem = XMODEM(getc=dummy_getc, putc=dummy_putc, mode=mode)
+    # exercise
+    with pytest.raises(ValueError):
+        status = modem.send(BytesIO(b'dummy-stream'))
+
+
 @pytest.mark.parametrize('mode', ['xmodem', 'xmodem1k'])
 def test_xmodem_dummy_fails_send(mode):
     # given,
-    modem = xmodem.XMODEM(getc=dummy_getc,
-                          putc=dummy_putc,
-                          mode=mode)
+    modem = XMODEM(getc=dummy_getc, putc=dummy_putc, mode=mode)
     # exercise
     status = modem.send(BytesIO(b'dummy-stream'))
     # verify
     assert not status, ("Expected value of status `False'")
 
 
-def test_xmodem_bad_mode():
+@pytest.mark.parametrize('mode', ['xmodem', 'xmodem1k'])
+def test_xmodem_send_exceed_maximum_number_of_resend(mode):
     # given,
-    mode = 'XXX'
-    modem = xmodem.XMODEM(getc=dummy_getc,
-                          putc=dummy_putc,
-                          mode=mode)
+    max_resend = 16
+
+    def generator():
+        if mode == 'xmodem':
+            yield NAK
+        else:
+            yield CRC
+        yield ACK
+        yield ACK
+
+        for i in range(max_resend + 1):
+            yield None
+
+    mock = generator()
+
+    def getc(size, timeout=1):
+        x = mock.next()
+        print("mock_getc => ", x)
+        return x
+
+    def putc(data, timeout=1):
+        return 0
+
+    xmodem = XMODEM(getc=getc, putc=putc, mode=mode)
     # exercise
-    with pytest.raises(ValueError):
-        status = modem.send(BytesIO(b'dummy-stream'))
+    assert xmodem.send(stream = BytesIO(b'dummy-stream'), retry=max_resend) == None
+
+
+@pytest.mark.parametrize('mode', ['xmodem', 'xmodem1k'])
+def test_xmodem_send_fails_once_each_packet_short_ByteIO(mode):
+    # given,
+    max_resend = 16
+
+    def generator():
+        if mode == 'xmodem':
+            yield NAK
+        else:
+            yield CRC
+
+        while True:
+            yield None
+            yield ACK
+
+    mock = generator()
+
+    def getc(size, timeout=1):
+        x = mock.next()
+        print("mock_getc => ", x)
+        return x
+
+    def putc(data, timeout=1):
+        return 0
+
+    xmodem = XMODEM(getc=getc, putc=putc, mode=mode)
+    # exercise
+    assert xmodem.send(stream=BytesIO(b'dummy-stream'), retry=max_resend)
+
+
+@pytest.mark.parametrize('mode', ['xmodem', 'xmodem1k'])
+def test_xmodem_send_fails_once_each_packet_long_ByteIO(mode):
+    # given,
+    max_resend = 16
+
+    def generator():
+        if mode == 'xmodem':
+            yield NAK
+        else:
+            yield CRC
+
+        yield ACK
+        for i in range(10):
+            yield None
+            yield ACK
+
+        yield ACK
+        yield ACK
+
+        for i in range(10):
+            yield None
+            yield ACK
+
+        while True:
+            ACK
+
+    mock = generator()
+
+    def getc(size, timeout=1):
+        x = mock.next()
+        print("[]mock_getc => ", x)
+        return x
+
+    def putc(data, timeout=1):
+        return 0
+
+    xmodem = XMODEM(getc=getc, putc=putc, mode=mode)
+    # exercise
+    assert xmodem.send(stream=BytesIO(b'dummy-stream'*30), retry=max_resend)