diff --git a/config.json b/config.json
index 75ebd28bf80..0415e630d15 100644
--- a/config.json
+++ b/config.json
@@ -1482,6 +1482,18 @@
         "loops"
       ]
     },
+    {
+      "slug": "paasio",
+      "uuid": "ec36f9ed-f376-43d9-90ee-be0bea0cfc98",
+      "core": false,
+      "unlocked_by": "book-store",
+      "difficulty": 5,
+      "topics": [
+        "classes",
+        "interfaces",
+        "networking"
+      ]
+    },
     {
       "slug": "accumulate",
       "uuid": "e7351e8e-d3ff-4621-b818-cd55cf05bffd",
diff --git a/exercises/paasio/README.md b/exercises/paasio/README.md
new file mode 100644
index 00000000000..a031f124666
--- /dev/null
+++ b/exercises/paasio/README.md
@@ -0,0 +1,60 @@
+# PaaS I/O
+
+Report network IO statistics.
+
+You are writing a [PaaS][], and you need a way to bill customers based
+on network and filesystem usage.
+
+Create a wrapper for network connections and files that can report IO
+statistics. The wrapper must report:
+
+- The total number of bytes read/written.
+- The total number of read/write operations.
+
+[PaaS]: http://en.wikipedia.org/wiki/Platform_as_a_service
+
+## Exception messages
+
+Sometimes it is necessary to raise an exception. When you do this, you should include a meaningful error message to
+indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. Not
+every exercise will require you to raise an exception, but for those that do, the tests will only pass if you include
+a message.
+
+To raise a message with an exception, just write it as an argument to the exception type. For example, instead of
+`raise Exception`, you should write:
+
+```python
+raise Exception("Meaningful message indicating the source of the error")
+```
+
+## Running the tests
+
+To run the tests, run `pytest paasio_test.py`
+
+Alternatively, you can tell Python to run the pytest module:
+`python -m pytest paasio_test.py`
+
+### Common `pytest` options
+
+- `-v` : enable verbose output
+- `-x` : stop running tests on first failure
+- `--ff` : run failures from previous test before running other test cases
+
+For other options, see `python -m pytest -h`
+
+## Submitting Exercises
+
+Note that, when trying to submit an exercise, make sure the solution is in the `$EXERCISM_WORKSPACE/python/paasio` directory.
+
+You can find your Exercism workspace by running `exercism debug` and looking for the line that starts with `Workspace`.
+
+For more detailed information about running tests, code style and linting,
+please see [Running the Tests](http://exercism.io/tracks/python/tests).
+
+## Source
+
+Brian Matsuo [https://github.com/bmatsuo](https://github.com/bmatsuo)
+
+## Submitting Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have completed the exercise.
diff --git a/exercises/paasio/example.py b/exercises/paasio/example.py
new file mode 100644
index 00000000000..54a404a68bd
--- /dev/null
+++ b/exercises/paasio/example.py
@@ -0,0 +1,102 @@
+import io
+
+
+class MeteredFile(io.BufferedRandom):
+    """Implement using a subclassing model."""
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._read_bytes = 0
+        self._read_ops = 0
+        self._write_bytes = 0
+        self._write_ops = 0
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        return super().__exit__(exc_type, exc_val, exc_tb)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        self._read_ops += 1
+        data = super().readline()
+        self._read_bytes += len(data)
+        if data:
+            return data
+        raise StopIteration
+
+    def read(self, size=-1):
+        self._read_ops += 1
+        data = super().read(size)
+        self._read_bytes += len(data)
+        return data
+
+    @property
+    def read_bytes(self):
+        return self._read_bytes
+
+    @property
+    def read_ops(self):
+        return self._read_ops
+
+    def write(self, b):
+        self._write_ops += 1
+        length = super().write(b)
+        self._write_bytes += length
+        return length
+
+    @property
+    def write_bytes(self):
+        return self._write_bytes
+
+    @property
+    def write_ops(self):
+        return self._write_ops
+
+
+class MeteredSocket:
+    """Implement using a delegation model."""
+
+    def __init__(self, socket):
+        self._socket = socket
+        self._recv_bytes = 0
+        self._recv_ops = 0
+        self._send_bytes = 0
+        self._send_ops = 0
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        return self._socket.__exit__(exc_type, exc_val, exc_tb)
+
+    def recv(self, bufsize, flags=0):
+        self._recv_ops += 1
+        data = self._socket.recv(bufsize, flags)
+        self._recv_bytes += len(data)
+        return data
+
+    @property
+    def recv_bytes(self):
+        return self._recv_bytes
+
+    @property
+    def recv_ops(self):
+        return self._recv_ops
+
+    def send(self, data, flags=0):
+        self._send_ops += 1
+        length = self._socket.send(data, flags)
+        self._send_bytes += length
+        return length
+
+    @property
+    def send_bytes(self):
+        return self._send_bytes
+
+    @property
+    def send_ops(self):
+        return self._send_ops
diff --git a/exercises/paasio/paasio.py b/exercises/paasio/paasio.py
new file mode 100644
index 00000000000..62987c6a295
--- /dev/null
+++ b/exercises/paasio/paasio.py
@@ -0,0 +1,77 @@
+import io
+
+
+class MeteredFile(io.BufferedRandom):
+    """Implement using a subclassing model."""
+
+    def __init__(self, *args, **kwargs):
+        pass
+
+    def __enter__(self):
+        pass
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        pass
+
+    def __iter__(self):
+        pass
+
+    def __next__(self):
+        pass
+
+    def read(self, size=-1):
+        pass
+
+    @property
+    def read_bytes(self):
+        pass
+
+    @property
+    def read_ops(self):
+        pass
+
+    def write(self, b):
+        pass
+
+    @property
+    def write_bytes(self):
+        pass
+
+    @property
+    def write_ops(self):
+        pass
+
+
+class MeteredSocket:
+    """Implement using a delegation model."""
+
+    def __init__(self, socket):
+        pass
+
+    def __enter__(self):
+        pass
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        pass
+
+    def recv(self, bufsize, flags=0):
+        pass
+
+    @property
+    def recv_bytes(self):
+        pass
+
+    @property
+    def recv_ops(self):
+        pass
+
+    def send(self, data, flags=0):
+        pass
+
+    @property
+    def send_bytes(self):
+        pass
+
+    @property
+    def send_ops(self):
+        pass
diff --git a/exercises/paasio/paasio_test.py b/exercises/paasio/paasio_test.py
new file mode 100644
index 00000000000..9e3612b5192
--- /dev/null
+++ b/exercises/paasio/paasio_test.py
@@ -0,0 +1,884 @@
+import errno
+import inspect
+import io
+import logging
+import os
+import unittest
+from unittest.mock import ANY, call, NonCallableMagicMock, patch
+
+from paasio import MeteredFile, MeteredSocket
+
+
+LOGGER = logging.getLogger(__name__)
+
+ZEN = b"""Beautiful is better than ugly.
+Explicit is better than implicit.
+Simple is better than complex.
+Complex is better than complicated.
+Flat is better than nested.
+Sparse is better than dense.
+Readability counts.
+Special cases aren't special enough to break the rules.
+Although practicality beats purity.
+Errors should never pass silently.
+Unless explicitly silenced.
+In the face of ambiguity, refuse the temptation to guess.
+There should be one-- and preferably only one --obvious way to do it.
+Although that way may not be obvious at first unless you're Dutch.
+Now is better than never.
+Although never is often better than *right* now.
+If the implementation is hard to explain, it's a bad idea.
+If the implementation is easy to explain, it may be a good idea.
+Namespaces are one honking great idea -- let's do more of those!
+"""
+
+
+# Implementation tests begin on line 456
+# Code below this line consists of mocks and tests for mocks compliance
+
+
+class MockException(Exception):
+    pass
+
+
+class MockFile(io.BytesIO):
+    def __init__(self, *args, chunk=None, exception=None, **kwargs):
+        super(MockFile, self).__init__(*args, **kwargs)
+        self.__chunk = chunk
+        self.__exception = exception
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        ret = super(MockFile, self).__exit__(exc_type, exc_val, exc_tb)
+        if exc_type is not None and "suppress" in exc_val.args[0]:
+            return True
+        return ret
+
+    def read(self, size=-1):
+        if self.__exception is not None:
+            raise self.__exception
+        if self.__chunk is None:
+            return super(MockFile, self).read(size)
+        if size is None:
+            return super(MockFile, self).read(self.__chunk)
+        if size < 0:
+            return super(MockFile, self).read(self.__chunk)
+        return super(MockFile, self).read(min(self.__chunk, size))
+
+    def write(self, data):
+        if self.__chunk is None:
+            return super(MockFile, self).write(data)
+        return super(MockFile, self).write(data[: self.__chunk])
+
+
+class MockSock:
+    def __init__(self, *, chunk=None, exception=None):
+        self._recver = io.BytesIO(ZEN)
+        self._sender = io.BytesIO()
+        self.__closed = False
+        self.__chunk = chunk
+        self.__exception = exception
+        self.flags = None
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self._recver.close()
+        self._sender.close()
+        self.__closed = True
+        if exc_type is not None and "suppress" in exc_val.args[0]:
+            return True
+        return False
+
+    def recv(self, bufsize, flags=0):
+        if self.__closed:
+            raise OSError(errno.EBADF, os.strerror(errno.EBADF))
+        if bufsize is None:
+            raise TypeError(
+                "'NoneType' object cannot be interpreted as an integer"
+            )
+        if not isinstance(flags, int):
+            raise TypeError(
+                "an integer is required (got type {})".format(
+                    type(flags).__name__
+                )
+            )
+        self.flags = flags
+        if self.__exception is not None:
+            raise self.__exception
+        if self.__chunk is None:
+            return self._recver.read(bufsize)
+        else:
+            return self._recver.read(min(self.__chunk, bufsize))
+
+    def send(self, data, flags=0):
+        if self.__closed:
+            raise OSError(errno.EBADF, os.strerror(errno.EBADF))
+        if not isinstance(flags, int):
+            raise TypeError(
+                "an integer is required (got type {})".format(
+                    type(flags).__name__
+                )
+            )
+        self.flags = flags
+        if self.__chunk is None:
+            return self._sender.write(data)
+        return self._sender.write(data[: self.__chunk])
+
+
+class SuperMock:
+    """Mock for super().__init__ calls only, as mock.MagicMock cannot."""
+
+    def __init__(self, *args, **kwargs):
+        if self.initialized:
+            self.init_called += 1
+        else:
+            self.initialized = True
+
+    def __call__(self, *args, **kwargs):
+        frame = inspect.currentframe()
+        if frame is None:
+            raise RuntimeError("Could not get current frame object")
+        stack = inspect.getouterframes(frame)
+        if any(
+            frame[3] == "__init__" and "paasio" in frame[1] for frame in stack
+        ):
+            return self
+        else:
+            return self.mock_object
+
+    def __repr__(self):
+        return "<SuperMock at {} with mock object: {!r}>".format(
+            hex(id(self)), self.mock_object
+        )
+
+    mock_object = None
+    init_called = 0
+    initialized = False
+
+
+class MockTestCase(unittest.TestCase):
+    def setUp(self):
+        self.test_passed = False
+
+    def tearDown(self):
+        if not self.test_passed:
+            LOGGER.critical(
+                "\nError in mocks, please report to Exercism: %s", self.id()
+            )
+
+    def test_fixture_exception(self):
+        self.assertEqual(False, self.test_passed)
+        with self.assertLogs(__name__, level="CRITICAL") as logs:
+            self.tearDown()
+        self.assertEqual(1, len(logs.output))
+        self.assertRegex(logs.output[0], ":\nError in mocks")
+        self.assertRegex(logs.output[0], "{}$".format(self.id()))
+        self.test_passed = True
+
+
+class SuperMockTest(MockTestCase):
+    def test_super_mock_repr(self):
+        mock = SuperMock()
+        expected = "<SuperMock at {} with mock object: {}>".format(
+            hex(id(mock)), repr(None)
+        )
+        self.assertEqual(expected, repr(mock))
+        file = MockFile()
+        mock.mock_object = file
+        expected = "<SuperMock at {} with mock object: {}>".format(
+            hex(id(mock)), repr(file)
+        )
+        self.assertEqual(expected, repr(mock))
+        self.test_passed = True
+
+    def test_super_mock_init(self):
+        self.assertIs(False, SuperMock.initialized)
+        mock = SuperMock()
+        self.assertIs(True, mock.initialized)
+        for calls in range(5):
+            self.assertEqual(calls, mock.init_called)
+            mock.__init__()
+        self.test_passed = True
+
+    def test_super_mock_call(self):
+        def call2(obj):
+            return obj()
+
+        def __init__(obj):
+            ret = call2(obj)
+            self.assertEqual(obj(), ret)
+            return ret
+
+        mock = SuperMock()
+        self.assertIs(None, mock.mock_object)
+        wrapped = object()
+        mock.mock_object = wrapped
+        self.assertIs(wrapped, mock())
+        self.assertIs(mock, __init__(mock))
+        self.test_passed = True
+
+    @patch("inspect.currentframe", return_value=None)
+    def test_super_mock_frame_error(self, inspect_mock):
+        with self.assertRaisesRegex(
+            RuntimeError, "^Could not get current frame object$"
+        ):
+            SuperMock()()
+        self.test_passed = True
+
+
+class MockSockTest(MockTestCase):
+    def test_context_manager(self):
+        with MockSock() as socket:
+            socket.recv(30)
+            socket.send(b"data")
+        with self.assertRaisesRegex(OSError, os.strerror(errno.EBADF)):
+            socket.recv(30)
+        with self.assertRaisesRegex(OSError, os.strerror(errno.EBADF)):
+            socket.send(b"")
+        self.test_passed = True
+
+    def test_context_manager_exception_raise(self):
+        exception = MockException("Should raise")
+        with self.assertRaisesRegex(MockException, "Should raise") as err:
+            with MockSock(exception=exception) as socket:
+                socket.recv(4096)
+        self.assertEqual(exception, err.exception)
+        self.test_passed = True
+
+    def test_context_manager_exception_suppress(self):
+        exception = MockException("Should suppress")
+        with MockSock(exception=exception) as socket:
+            socket.recv(4096)
+        self.test_passed = True
+
+    def test_recv_once(self):
+        with MockSock() as socket:
+            actual_recv = socket.recv(4096)
+        self.assertEqual(ZEN, actual_recv)
+        self.test_passed = True
+
+    def test_recv_multiple(self):
+        actual_recv = b""
+        with MockSock() as socket:
+            for _ in range(5):
+                actual_recv += socket.recv(30)
+        self.assertEqual(ZEN[:150], actual_recv)
+        self.test_passed = True
+
+    def test_recv_multiple_chunk(self):
+        actual_recv = b""
+        with MockSock(chunk=20) as socket:
+            for _ in range(5):
+                actual_recv += socket.recv(4096)
+            actual_recv += socket.recv(10)
+        self.assertEqual(ZEN[:110], actual_recv)
+        self.test_passed = True
+
+    def test_recv_under_size(self):
+        with MockSock(chunk=257) as socket:
+            actual_recv = socket.recv(4096)
+        self.assertEqual(ZEN[:257], actual_recv)
+        self.test_passed = True
+
+    def test_send_once(self):
+        with MockSock(chunk=257) as socket:
+            send_len = socket.send(ZEN)
+            self.assertEqual(ZEN[:257], socket._sender.getbuffer())
+        self.assertEqual(257, send_len)
+        self.test_passed = True
+
+    def test_send_multiple(self):
+        send_len = 0
+        expected = b"Tomorrow's victory is today's practice."
+        with MockSock() as socket:
+            send_len += socket.send(b"Tomorro")
+            send_len += socket.send(b"w's victo")
+            send_len += socket.send(b"ry is today")
+            send_len += socket.send(b"'s practice.")
+            self.assertEqual(expected, socket._sender.getbuffer())
+        self.assertEqual(39, send_len)
+        self.test_passed = True
+
+    def test_send_under_size(self):
+        with MockSock(chunk=257) as socket:
+            send_len = socket.send(ZEN[:123])
+            self.assertEqual(ZEN[:123], socket._sender.getbuffer())
+        self.assertEqual(123, send_len)
+        self.test_passed = True
+
+    def test_bufsize_required(self):
+        with self.assertRaisesRegex(TypeError, "argument"):
+            with MockSock() as socket:
+                socket.recv()
+
+        with self.assertRaisesRegex(TypeError, "'NoneType'.+integer"):
+            with MockSock() as socket:
+                socket.recv(None)
+        self.test_passed = True
+
+    def test_flags_support(self):
+        with MockSock() as socket:
+            self.assertEqual(len(ZEN), socket.send(ZEN, 42))
+            self.assertEqual(ZEN, socket.recv(4096, 24))
+        with MockSock() as mock_sock:
+            self.assertIs(None, mock_sock.flags)
+            mock_sock.recv(50)
+            self.assertEqual(0, mock_sock.flags)
+            mock_sock.send(b"no flags")
+            self.assertEqual(0, mock_sock.flags)
+            mock_sock.recv(30, 30)
+            self.assertEqual(30, mock_sock.flags)
+            mock_sock.send(b"flags", 1024)
+            self.assertEqual(
+                1024, mock_sock.flags,
+            )
+            with self.assertRaisesRegex(
+                TypeError, r"^an integer is.+NoneType\)$"
+            ):
+                mock_sock.send(b"data", None)
+            with self.assertRaisesRegex(
+                TypeError, r"^an integer is.+bytes\)$"
+            ):
+                mock_sock.send(b"data", b"flags")
+            with self.assertRaisesRegex(
+                TypeError, r"^an integer is.+NoneType\)$"
+            ):
+                mock_sock.recv(b"data", None)
+            with self.assertRaisesRegex(
+                TypeError, r"^an integer is.+bytes\)$"
+            ):
+                mock_sock.recv(b"data", b"flags")
+        self.test_passed = True
+
+
+class MockFileTest(MockTestCase):
+    def test_context_manager(self):
+        with MockFile(ZEN) as file:
+            file.read()
+        with self.assertRaisesRegex(
+            ValueError, "I/O operation on closed file."
+        ):
+            file.read()
+        with self.assertRaisesRegex(
+            ValueError, "I/O operation on closed file."
+        ):
+            file.write(b"data")
+        self.test_passed = True
+
+    def test_context_manager_exception_raise(self):
+        exception = MockException("Should raise")
+        mock = MockFile(ZEN, exception=exception)
+        with self.assertRaisesRegex(MockException, "Should raise") as err:
+            with mock as file:
+                file.read()
+        self.assertEqual(exception, err.exception)
+        self.test_passed = True
+
+    def test_context_manager_exception_suppress(self):
+        exception = MockException("Should suppress")
+        mock = MockFile(ZEN, exception=exception)
+        with mock as file:
+            file.read()
+        self.test_passed = True
+
+    def test_read_once(self):
+        with MockFile(ZEN) as file:
+            actual_read = file.read()
+        self.assertEqual(ZEN, actual_read)
+
+        with MockFile(ZEN) as file:
+            actual_read = file.read(None)
+        self.assertEqual(ZEN, actual_read)
+
+        with MockFile(ZEN) as file:
+            actual_read = file.read(-1)
+        self.assertEqual(ZEN, actual_read)
+        self.test_passed = True
+
+    def test_read_multiple(self):
+        actual_read = b""
+        with MockFile(ZEN) as file:
+            for _ in range(5):
+                actual_read += file.read(30)
+        self.assertEqual(ZEN[:150], actual_read)
+        self.test_passed = True
+
+    def test_read_multiple_chunk(self):
+        actual_read = b""
+        with MockFile(ZEN, chunk=20) as file:
+            for _ in range(5):
+                actual_read += file.read()
+            actual_read += file.read(10)
+        self.assertEqual(ZEN[:110], actual_read)
+
+        actual_read = b""
+        with MockFile(ZEN, chunk=20) as file:
+            for size in [None, -2, -1, 0, 1, 2]:
+                actual_read += file.read(size)
+            actual_read += file.read(10)
+        self.assertEqual(ZEN[:73], actual_read)
+        self.test_passed = True
+
+    def test_read_under_size(self):
+        with MockFile(ZEN, chunk=257) as file:
+            actual_read = file.read()
+        self.assertEqual(ZEN[:257], actual_read)
+        self.test_passed = True
+
+    def test_write_once(self):
+        with MockFile(chunk=257) as file:
+            write_len = file.write(ZEN)
+            self.assertEqual(ZEN[:257], file.getbuffer())
+            self.assertEqual(257, write_len)
+        self.test_passed = True
+
+    def test_write_multiple(self):
+        write_len = 0
+        expected = b"Tomorrow's victory is today's practice."
+        with MockFile() as file:
+            write_len += file.write(b"Tomorro")
+            write_len += file.write(b"w's victo")
+            write_len += file.write(b"ry is today")
+            write_len += file.write(b"'s practice.")
+            self.assertEqual(expected, file.getbuffer())
+            self.assertEqual(len(expected), write_len)
+        self.test_passed = True
+
+    def test_write_under_size(self):
+        with MockFile(chunk=257) as file:
+            write_len = file.write(ZEN[:123])
+            self.assertEqual(ZEN[:123], file.getbuffer())
+            self.assertEqual(123, write_len)
+        self.test_passed = True
+
+
+# Tests for paasio.py begin here
+
+
+class MeteredSocketTest(unittest.TestCase):
+    def test_context_manager(self):
+        wrapped = MockSock()
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        mock.__exit__.side_effect = wrapped.__exit__
+        with MeteredSocket(mock) as socket:
+            self.assertFalse(mock.__enter__.called)
+            socket.recv(30)
+        self.assertFalse(mock.__enter__.called)
+        mock.__exit__.assert_called_once_with(None, None, None)
+        self.assertEqual(2, len(mock.mock_calls))
+        with self.assertRaisesRegex(OSError, os.strerror(errno.EBADF)):
+            socket.recv(30)
+        with self.assertRaisesRegex(OSError, os.strerror(errno.EBADF)):
+            socket.send(b"")
+
+    def test_context_manager_exception_raise(self):
+        exception = MockException("Should raise")
+        wrapped = MockSock(exception=exception)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        mock.__exit__.side_effect = wrapped.__exit__
+        with self.assertRaisesRegex(MockException, "Should raise") as err:
+            with MeteredSocket(mock) as socket:
+                self.assertFalse(mock.__enter__.called)
+                socket.recv(4096)
+        self.assertFalse(mock.__enter__.called)
+        mock.__exit__.assert_called_once_with(
+            MockException, err.exception, ANY,
+        )
+        self.assertEqual(exception, err.exception)
+
+    def test_context_manager_exception_suppress(self):
+        exception = MockException("Should suppress")
+        wrapped = MockSock(exception=exception)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        mock.__exit__.side_effect = wrapped.__exit__
+        with MeteredSocket(mock) as socket:
+            self.assertFalse(mock.__enter__.called)
+            socket.recv(4096)
+        self.assertFalse(mock.__enter__.called)
+        mock.__exit__.assert_called_once_with(
+            MockException, exception, ANY,
+        )
+
+    def test_recv_once(self):
+        mock = NonCallableMagicMock(wraps=MockSock(), autospec=True)
+        with MeteredSocket(mock) as socket:
+            actual_recv = socket.recv(4096)
+        self.assertEqual(ZEN, actual_recv)
+        self.assertEqual(1, socket.recv_ops)
+        self.assertEqual(len(ZEN), socket.recv_bytes)
+        self.assertEqual(1, mock.recv.call_count)
+
+    def test_recv_multiple(self):
+        wrapped = MockSock()
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        actual_recv = b""
+        with MeteredSocket(mock) as socket:
+            for _ in range(5):
+                actual_recv += socket.recv(30)
+        self.assertEqual(ZEN[:150], actual_recv)
+        self.assertEqual(5, socket.recv_ops)
+        self.assertEqual(150, socket.recv_bytes)
+        self.assertEqual(5, mock.recv.call_count)
+
+    def test_recv_multiple_chunk(self):
+        wrapped = MockSock(chunk=20)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        actual_recv = b""
+        with MeteredSocket(mock) as socket:
+            for _ in range(5):
+                actual_recv += socket.recv(4096)
+            actual_recv += socket.recv(10)
+        self.assertEqual(ZEN[:110], actual_recv)
+        self.assertEqual(6, socket.recv_ops)
+        self.assertEqual(110, socket.recv_bytes)
+        self.assertEqual(6, mock.recv.call_count)
+
+    def test_recv_under_size(self):
+        wrapped = MockSock(chunk=257)  # largish odd number
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        with MeteredSocket(mock) as socket:
+            actual_recv = socket.recv(4096)
+        self.assertEqual(ZEN[:257], actual_recv)
+        self.assertEqual(1, socket.recv_ops)
+        self.assertEqual(257, socket.recv_bytes)
+        self.assertEqual(1, mock.recv.call_count)
+
+    def test_send_once(self):
+        wrapped = MockSock(chunk=257)  # largish odd number
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        with MeteredSocket(mock) as socket:
+            send_len = socket.send(ZEN)
+            self.assertEqual(ZEN[:257], wrapped._sender.getbuffer())
+        self.assertEqual(257, send_len)
+        self.assertEqual(1, socket.send_ops)
+        self.assertEqual(257, socket.send_bytes)
+        self.assertEqual(1, mock.send.call_count)
+
+    def test_send_multiple(self):
+        wrapped = MockSock()
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        send_len = 0
+        expected = b"Tomorrow's victory is today's practice."
+        with MeteredSocket(mock) as socket:
+            send_len += socket.send(b"Tomorro")
+            send_len += socket.send(b"w's victo")
+            send_len += socket.send(b"ry is today")
+            send_len += socket.send(b"'s practice.")
+            self.assertEqual(expected, wrapped._sender.getbuffer())
+        self.assertEqual(39, send_len)
+        self.assertEqual(4, socket.send_ops)
+        self.assertEqual(39, socket.send_bytes)
+        self.assertEqual(4, mock.send.call_count)
+
+    def test_send_under_size(self):
+        wrapped = MockSock(chunk=257)  # largish odd number
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        with MeteredSocket(mock) as socket:
+            send_len = socket.send(ZEN[:123])
+            self.assertEqual(ZEN[:123], wrapped._sender.getbuffer())
+        self.assertEqual(123, send_len)
+        self.assertEqual(1, socket.send_ops)
+        self.assertEqual(123, socket.send_bytes)
+        self.assertEqual(1, mock.send.call_count)
+
+    def test_bufsize_required(self):
+        mock = NonCallableMagicMock(wraps=MockSock(), autospec=True)
+        with self.assertRaisesRegex(TypeError, "argument"):
+            with MeteredSocket(mock) as socket:
+                socket.recv()
+        self.assertFalse(mock.recv.called)
+
+        mock = NonCallableMagicMock(wraps=MockSock(), autospec=True)
+        with self.assertRaisesRegex(TypeError, "^'NoneType'.+integer$"):
+            with MeteredSocket(mock) as socket:
+                socket.recv(None)
+        self.assertTrue(
+            call(None) in mock.recv.mock_calls
+            or call(None, ANY) in mock.recv.mock_calls
+        )
+
+    def test_flags_support(self):
+        mock = NonCallableMagicMock(wraps=MockSock(), autospec=True)
+        with MeteredSocket(mock) as socket:
+            self.assertEqual(len(ZEN), socket.send(ZEN, 42))
+            self.assertEqual(ZEN, socket.recv(4096, 24))
+        mock.send.assert_called_once_with(ZEN, 42)
+        mock.recv.assert_called_once_with(4096, 24)
+
+        wrapped = MockSock()
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        with MeteredSocket(mock) as socket:
+            socket.recv(50)
+            self.assertEqual(0, wrapped.flags)
+            socket.send(b"no flags")
+            self.assertEqual(0, wrapped.flags)
+            socket.recv(30, 30)
+            self.assertEqual(30, wrapped.flags)
+            socket.send(b"flags", 1024)
+            self.assertEqual(1024, wrapped.flags)
+            with self.assertRaisesRegex(TypeError, "integer is required"):
+                socket.send(b"data", None)
+            with self.assertRaisesRegex(TypeError, "integer is required"):
+                socket.send(b"data", b"flags")
+            with self.assertRaisesRegex(TypeError, "integer is required"):
+                socket.recv(b"data", None)
+            with self.assertRaisesRegex(TypeError, "integer is required"):
+                socket.recv(b"data", b"flags")
+
+    def test_stats_read_only(self):
+        mock = NonCallableMagicMock(wraps=MockSock(), autospec=True)
+        with MeteredSocket(mock) as socket:
+            self.assertEqual(0, socket.send_ops)
+            self.assertEqual(0, socket.send_bytes)
+            self.assertEqual(0, socket.recv_ops)
+            self.assertEqual(0, socket.recv_bytes)
+            for _ in range(277):
+                socket.send(b"b")
+            socket.send(b"bytes")
+            for _ in range(257):
+                socket.recv(1)
+            socket.recv(2)
+            self.assertEqual(278, socket.send_ops)
+            self.assertEqual(282, socket.send_bytes)
+            self.assertEqual(258, socket.recv_ops)
+            self.assertEqual(259, socket.recv_bytes)
+            with self.assertRaisesRegex(AttributeError, "can't set"):
+                socket.send_ops = 0
+            with self.assertRaisesRegex(AttributeError, "can't set"):
+                socket.send_bytes = 0
+            with self.assertRaisesRegex(AttributeError, "can't set"):
+                socket.recv_ops = 0
+            with self.assertRaisesRegex(AttributeError, "can't set"):
+                socket.recv_bytes = 0
+            self.assertEqual(278, socket.send_ops)
+            self.assertEqual(282, socket.send_bytes)
+            self.assertEqual(258, socket.recv_ops)
+            self.assertEqual(259, socket.recv_bytes)
+
+
+@patch("paasio.super", create=True, new_callable=SuperMock)
+class MeteredFileTest(unittest.TestCase):
+    def test_context_manager(self, super_mock):
+        wrapped = MockFile(ZEN)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        mock.__exit__.side_effect = wrapped.__exit__
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            self.assertEqual(1, super_mock.init_called)
+            self.assertFalse(mock.__enter__.called)
+            file.read()
+        self.assertFalse(mock.__enter__.called)
+        mock.__exit__.assert_called_once_with(None, None, None)
+        self.assertEqual(2, len(mock.mock_calls))
+        with self.assertRaisesRegex(
+            ValueError, "I/O operation on closed file."
+        ):
+            file.read()
+        with self.assertRaisesRegex(
+            ValueError, "I/O operation on closed file."
+        ):
+            file.write(b"data")
+
+    def test_context_manager_exception_raise(self, super_mock):
+        exception = MockException("Should raise")
+        wrapped = MockFile(ZEN, exception=exception)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        mock.__exit__.side_effect = wrapped.__exit__
+        super_mock.mock_object = mock
+        with self.assertRaisesRegex(MockException, "Should raise") as err:
+            with MeteredFile() as file:
+                self.assertFalse(mock.__enter__.called)
+                file.read()
+        self.assertFalse(mock.__enter__.called)
+        mock.__exit__.assert_called_once_with(
+            MockException, err.exception, ANY,
+        )
+        self.assertEqual(exception, err.exception)
+
+    def test_context_manager_exception_suppress(self, super_mock):
+        exception = MockException("Should suppress")
+        wrapped = MockFile(ZEN, exception=exception)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        mock.__exit__.side_effect = wrapped.__exit__
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            self.assertFalse(mock.__enter__.called)
+            file.read()
+        self.assertFalse(mock.__enter__.called)
+        mock.__exit__.assert_called_once_with(
+            MockException, exception, ANY,
+        )
+
+    def test_iteration(self, super_mock):
+        mock = NonCallableMagicMock(wraps=MockFile(ZEN), autospec=True)
+        super_mock.mock_object = mock
+        actual_reads = b""
+        file = MeteredFile()
+        for line in file:
+            actual_reads += line
+            self.assertLess(
+                0, mock.readline.call_count, "File's readline not called"
+            )
+            self.assertGreater(
+                50, mock.readline.call_count, "Possible infinte loop detected"
+            )
+            self.assertEqual(file.read_ops, mock.readline.call_count)
+        self.assertFalse(mock.__iter__.called)
+        self.assertEqual(len(ZEN), file.read_bytes)
+        self.assertEqual(ZEN, actual_reads)
+
+    def test_read_once(self, super_mock):
+        mock = NonCallableMagicMock(wraps=MockFile(ZEN), autospec=True)
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            actual_read = file.read()
+        self.assertEqual(ZEN, actual_read)
+        self.assertEqual((len(ZEN)), file.read_bytes)
+        self.assertEqual(1, file.read_ops)
+        self.assertEqual(mock.read.call_count, file.read_ops)
+
+        mock = NonCallableMagicMock(wraps=MockFile(ZEN), autospec=True)
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            actual_read = file.read(None)
+        self.assertEqual(ZEN, actual_read)
+        self.assertEqual((len(ZEN)), file.read_bytes)
+        self.assertEqual(1, file.read_ops)
+        self.assertEqual(mock.read.call_count, file.read_ops)
+
+        mock = NonCallableMagicMock(wraps=MockFile(ZEN), autospec=True)
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            actual_read = file.read(-1)
+        self.assertEqual(ZEN, actual_read)
+        self.assertEqual((len(ZEN)), file.read_bytes)
+        self.assertEqual(1, file.read_ops)
+        self.assertEqual(mock.read.call_count, file.read_ops)
+
+    def test_read_multiple(self, super_mock):
+        wrapped = MockFile(ZEN)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        super_mock.mock_object = mock
+        actual_read = b""
+        with MeteredFile() as file:
+            for _ in range(5):
+                actual_read += file.read(30)
+        self.assertEqual(ZEN[:150], actual_read)
+        self.assertEqual(5, file.read_ops)
+        self.assertEqual(150, file.read_bytes)
+        self.assertEqual(5, mock.read.call_count)
+
+    def test_read_multiple_chunk(self, super_mock):
+        wrapped = MockFile(ZEN, chunk=20)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        super_mock.mock_object = mock
+        actual_read = b""
+        with MeteredFile() as file:
+            for _ in range(5):
+                actual_read += file.read()
+            actual_read += file.read(10)
+        self.assertEqual(ZEN[:110], actual_read)
+        self.assertEqual(6, file.read_ops)
+        self.assertEqual(110, file.read_bytes)
+        self.assertEqual(6, mock.read.call_count)
+
+        wrapped = MockFile(ZEN, chunk=20)
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        super_mock.mock_object = mock
+        actual_read = b""
+        with MeteredFile() as file:
+            for size in [None, -2, -1, 0, 1, 2]:
+                actual_read += file.read(size)
+            actual_read += file.read(10)
+        self.assertEqual(ZEN[:73], actual_read)
+        self.assertEqual(7, file.read_ops)
+        self.assertEqual(73, file.read_bytes)
+        self.assertEqual(7, mock.read.call_count)
+
+    def test_read_under_size(self, super_mock):
+        wrapped = MockFile(ZEN, chunk=257)  # largish odd number
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            actual_read = file.read()
+        self.assertEqual(ZEN[:257], actual_read)
+        self.assertEqual(1, file.read_ops)
+        self.assertEqual(257, file.read_bytes)
+        self.assertEqual(1, mock.read.call_count)
+
+    def test_write_once(self, super_mock):
+        wrapped = MockFile(chunk=257)  # largish odd number
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            write_len = file.write(ZEN)
+            self.assertEqual(ZEN[:257], wrapped.getbuffer())
+        self.assertEqual(257, write_len)
+        self.assertEqual(1, file.write_ops)
+        self.assertEqual(257, file.write_bytes)
+        self.assertEqual(1, mock.write.call_count)
+
+    def test_write_multiple(self, super_mock):
+        wrapped = MockFile()
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        super_mock.mock_object = mock
+        write_len = 0
+        expected = b"Tomorrow's victory is today's practice."
+        with MeteredFile() as file:
+            write_len += file.write(b"Tomorro")
+            write_len += file.write(b"w's victo")
+            write_len += file.write(b"ry is today")
+            write_len += file.write(b"'s practice.")
+            self.assertEqual(expected, wrapped.getbuffer())
+        self.assertEqual(39, write_len)
+        self.assertEqual(4, file.write_ops)
+        self.assertEqual(39, file.write_bytes)
+        self.assertEqual(4, mock.write.call_count)
+
+    def test_write_under_size(self, super_mock):
+        wrapped = MockFile(chunk=257)  # largish odd number
+        mock = NonCallableMagicMock(wraps=wrapped, autospec=True)
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            write_len = file.write(ZEN[:123])
+            self.assertEqual(ZEN[:123], wrapped.getbuffer())
+        self.assertEqual(123, write_len)
+        self.assertEqual(1, file.write_ops)
+        self.assertEqual(123, file.write_bytes)
+        self.assertEqual(1, mock.write.call_count)
+
+    def test_stats_read_only(self, super_mock):
+        mock = NonCallableMagicMock(wraps=MockFile(ZEN), autospec=True)
+        super_mock.mock_object = mock
+        with MeteredFile() as file:
+            self.assertEqual(0, file.read_ops)
+            self.assertEqual(0, file.read_bytes)
+            for _ in range(57):
+                file.read(1)
+            file.read(2)
+            self.assertEqual(58, file.read_ops)
+            self.assertEqual(59, file.read_bytes)
+            self.assertEqual(0, file.write_ops)
+            self.assertEqual(0, file.write_bytes)
+            for _ in range(77):
+                file.write(b"b")
+            file.write(b"bytes")
+            self.assertEqual(78, file.write_ops)
+            self.assertEqual(82, file.write_bytes)
+            with self.assertRaisesRegex(AttributeError, "can't set"):
+                file.write_ops = 0
+            with self.assertRaisesRegex(AttributeError, "can't set"):
+                file.write_bytes = 0
+            with self.assertRaisesRegex(AttributeError, "can't set"):
+                file.read_ops = 0
+            with self.assertRaisesRegex(AttributeError, "can't set"):
+                file.read_bytes = 0
+            self.assertEqual(78, file.write_ops)
+            self.assertEqual(82, file.write_bytes)
+            self.assertEqual(58, file.read_ops)
+            self.assertEqual(59, file.read_bytes)
+
+
+if __name__ == "__main__":
+    unittest.main()