diff --git a/great_ai/external/__init__.py b/great_ai/external/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/great_ai/external/async_lru.py b/great_ai/external/async_lru.py
new file mode 100644
index 0000000..c209d5a
--- /dev/null
+++ b/great_ai/external/async_lru.py
@@ -0,0 +1,192 @@
+import asyncio
+from collections import OrderedDict
+from functools import _CacheInfo, _make_key, partial, wraps
+
+__version__ = "1.0.3"
+
+__all__ = ("alru_cache",)
+
+
+def unpartial(fn):
+    while hasattr(fn, "func"):
+        fn = fn.func
+
+    return fn
+
+
+def _done_callback(fut, task):
+    if task.cancelled():
+        fut.cancel()
+        return
+
+    exc = task.exception()
+    if exc is not None:
+        fut.set_exception(exc)
+        return
+
+    fut.set_result(task.result())
+
+
+def _cache_invalidate(wrapped, typed, *args, **kwargs):
+    key = _make_key(args, kwargs, typed)
+
+    exists = key in wrapped._cache
+
+    if exists:
+        wrapped._cache.pop(key)
+
+    return exists
+
+
+def _cache_clear(wrapped):
+    wrapped.hits = wrapped.misses = 0
+    wrapped._cache = OrderedDict()
+    wrapped.tasks = set()
+
+
+def _open(wrapped):
+    if not wrapped.closed:
+        raise RuntimeError("alru_cache is not closed")
+
+    was_closed = (
+        wrapped.hits == wrapped.misses == len(wrapped.tasks) == len(wrapped._cache) == 0
+    )
+
+    if not was_closed:
+        raise RuntimeError("alru_cache was not closed correctly")
+
+    wrapped.closed = False
+
+
+def _close(wrapped, *, cancel=False, return_exceptions=True):
+    if wrapped.closed:
+        raise RuntimeError("alru_cache is closed")
+
+    wrapped.closed = True
+
+    if cancel:
+        for task in wrapped.tasks:
+            if not task.done():  # not sure is it possible
+                task.cancel()
+
+    return _wait_closed(wrapped, return_exceptions=return_exceptions)
+
+
+async def _wait_closed(wrapped, *, return_exceptions):
+    wait_closed = asyncio.gather(*wrapped.tasks, return_exceptions=return_exceptions)
+
+    wait_closed.add_done_callback(partial(_close_waited, wrapped))
+
+    ret = await wait_closed
+
+    # hack to get _close_waited callback to be executed
+    await asyncio.sleep(0)
+
+    return ret
+
+
+def _close_waited(wrapped, _):
+    wrapped.cache_clear()
+
+
+def _cache_info(wrapped, maxsize):
+    return _CacheInfo(
+        wrapped.hits,
+        wrapped.misses,
+        maxsize,
+        len(wrapped._cache),
+    )
+
+
+def __cache_touch(wrapped, key):
+    try:
+        wrapped._cache.move_to_end(key)
+    except KeyError:  # not sure is it possible
+        pass
+
+
+def _cache_hit(wrapped, key):
+    wrapped.hits += 1
+    __cache_touch(wrapped, key)
+
+
+def _cache_miss(wrapped, key):
+    wrapped.misses += 1
+    __cache_touch(wrapped, key)
+
+
+def alru_cache(
+    fn=None,
+    maxsize=128,
+    typed=False,
+    *,
+    cache_exceptions=True,
+):
+    def wrapper(fn):
+        _origin = unpartial(fn)
+
+        if not asyncio.iscoroutinefunction(_origin):
+            raise RuntimeError("Coroutine function is required, got {}".format(fn))
+
+        # functools.partialmethod support
+        if hasattr(fn, "_make_unbound_method"):
+            fn = fn._make_unbound_method()
+
+        @wraps(fn)
+        async def wrapped(*fn_args, **fn_kwargs):
+            if wrapped.closed:
+                raise RuntimeError("alru_cache is closed for {}".format(wrapped))
+
+            loop = asyncio.get_event_loop()
+
+            key = _make_key(fn_args, fn_kwargs, typed)
+
+            fut = wrapped._cache.get(key)
+
+            if fut is not None:
+                if not fut.done():
+                    _cache_hit(wrapped, key)
+                    return await asyncio.shield(fut)
+
+                exc = fut._exception
+
+                if exc is None or cache_exceptions:
+                    _cache_hit(wrapped, key)
+                    return fut.result()
+
+                # exception here and cache_exceptions == False
+                wrapped._cache.pop(key)
+
+            fut = loop.create_future()
+            task = loop.create_task(fn(*fn_args, **fn_kwargs))
+            task.add_done_callback(partial(_done_callback, fut))
+
+            wrapped.tasks.add(task)
+            task.add_done_callback(wrapped.tasks.remove)
+
+            wrapped._cache[key] = fut
+
+            if maxsize is not None and len(wrapped._cache) > maxsize:
+                wrapped._cache.popitem(last=False)
+
+            _cache_miss(wrapped, key)
+            return await asyncio.shield(fut)
+
+        _cache_clear(wrapped)
+        wrapped._origin = _origin
+        wrapped.closed = False
+        wrapped.cache_info = partial(_cache_info, wrapped, maxsize)
+        wrapped.cache_clear = partial(_cache_clear, wrapped)
+        wrapped.invalidate = partial(_cache_invalidate, wrapped, typed)
+        wrapped.close = partial(_close, wrapped)
+        wrapped.open = partial(_open, wrapped)
+
+        return wrapped
+
+    if fn is None:
+        return wrapper
+
+    if callable(fn) or hasattr(fn, "_make_unbound_method"):
+        return wrapper(fn)
+
+    raise NotImplementedError("{} decorating is not supported".format(fn))
diff --git a/tests/external/__init__.py b/tests/external/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/external/conftest.py b/tests/external/conftest.py
new file mode 100644
index 0000000..1fb0b17
--- /dev/null
+++ b/tests/external/conftest.py
@@ -0,0 +1,47 @@
+import asyncio
+import gc
+import os
+
+import pytest
+from great_ai.external.async_lru import _CacheInfo
+
+asyncio.set_event_loop(None)
+
+
+@pytest.fixture
+def event_loop(request):
+    loop = asyncio.new_event_loop()
+    loop.set_debug(bool(os.environ.get("PYTHONASYNCIODEBUG")))
+
+    yield loop
+
+    loop.call_soon(loop.stop)
+    loop.run_forever()
+    loop.close()
+
+    gc.collect()
+
+
+@pytest.fixture
+def loop(event_loop, request):
+    asyncio.set_event_loop(None)
+    request.addfinalizer(lambda: asyncio.set_event_loop(None))
+
+    return event_loop
+
+
+@pytest.fixture
+def check_lru(request):
+    def _check_lru(wrapped, *, hits, misses, cache, tasks, maxsize=128):
+        assert wrapped.hits == hits
+        assert wrapped.misses == misses
+        assert len(wrapped._cache) == cache
+        assert len(wrapped.tasks) == tasks
+        assert wrapped.cache_info() == _CacheInfo(
+            hits=hits,
+            misses=misses,
+            maxsize=maxsize,
+            currsize=cache,
+        )
+
+    return _check_lru
diff --git a/tests/external/test_basic.py b/tests/external/test_basic.py
new file mode 100644
index 0000000..604662d
--- /dev/null
+++ b/tests/external/test_basic.py
@@ -0,0 +1,187 @@
+import asyncio
+from functools import partial
+
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+alru_cache_attrs = [
+    "hits",
+    "misses",
+    "tasks",
+    "closed",
+    "cache_info",
+    "cache_clear",
+    "invalidate",
+    "close",
+    "open",
+]
+
+alru_cache_calable_attrs = alru_cache_attrs.copy()
+for attr in ["hits", "misses", "tasks", "closed"]:
+    alru_cache_calable_attrs.remove(attr)
+
+
+def test_alru_cache_not_callable(loop):
+    with pytest.raises(NotImplementedError):
+        alru_cache("foo")
+
+
+def test_alru_cache_not_coroutine(loop):
+    with pytest.raises(RuntimeError):
+
+        @alru_cache
+        def not_coro(val):
+            return val
+
+
+def test_alru_cache_deco(loop, check_lru):
+    asyncio.set_event_loop(loop)
+
+    @alru_cache
+    async def coro():
+        pass
+
+    assert asyncio.iscoroutinefunction(coro)
+
+    for attr in alru_cache_attrs:
+        assert hasattr(coro, attr)
+    for attr in alru_cache_calable_attrs:
+        assert callable(getattr(coro, attr))
+
+    assert isinstance(coro._cache, dict)
+    assert isinstance(coro.tasks, set)
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    awaitable = coro()
+    assert asyncio.iscoroutine(awaitable)
+    loop.run_until_complete(awaitable)
+
+
+def test_alru_cache_deco_called(check_lru, loop):
+    asyncio.set_event_loop(loop)
+
+    @alru_cache()
+    async def coro():
+        pass
+
+    assert asyncio.iscoroutinefunction(coro)
+
+    for attr in alru_cache_attrs:
+        assert hasattr(coro, attr)
+    for attr in alru_cache_calable_attrs:
+        assert callable(getattr(coro, attr))
+
+    assert isinstance(coro._cache, dict)
+    assert isinstance(coro.tasks, set)
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    awaitable = coro()
+    assert asyncio.iscoroutine(awaitable)
+    loop.run_until_complete(awaitable)
+
+
+def test_alru_cache_fn_called(check_lru, loop):
+    asyncio.set_event_loop(loop)
+
+    async def coro():
+        pass
+
+    coro_wrapped = alru_cache(coro)
+
+    assert asyncio.iscoroutinefunction(coro_wrapped)
+
+    for attr in alru_cache_attrs:
+        assert hasattr(coro_wrapped, attr)
+    for attr in alru_cache_calable_attrs:
+        assert callable(getattr(coro_wrapped, attr))
+
+    assert isinstance(coro_wrapped._cache, dict)
+    assert isinstance(coro_wrapped.tasks, set)
+    check_lru(coro_wrapped, hits=0, misses=0, cache=0, tasks=0)
+
+    awaitable = coro_wrapped()
+    assert asyncio.iscoroutine(awaitable)
+    loop.run_until_complete(awaitable)
+
+
+def test_alru_cache_origin(loop):
+    asyncio.set_event_loop(loop)
+
+    async def coro():
+        pass
+
+    coro_wrapped = alru_cache(coro)
+
+    assert coro_wrapped._origin is coro
+
+    coro_wrapped = alru_cache(partial(coro))
+
+    assert coro_wrapped._origin is coro
+
+
+@pytest.mark.asyncio
+async def test_alru_cache_await_same_result_async(check_lru, loop):
+    calls = 0
+    val = object()
+
+    @alru_cache()
+    async def coro():
+        nonlocal calls
+        calls += 1
+
+        return val
+
+    coros = [coro() for _ in range(100)]
+    ret = await asyncio.gather(*coros)
+    expected = [val] * 100
+    assert ret == expected
+    check_lru(coro, hits=99, misses=1, cache=1, tasks=0)
+
+    assert calls == 1
+    assert await coro() is val
+    check_lru(coro, hits=100, misses=1, cache=1, tasks=0)
+
+
+@pytest.mark.asyncio
+async def test_alru_cache_await_same_result_coroutine(check_lru, loop):
+    calls = 0
+    val = object()
+
+    @alru_cache()
+    async def coro():
+        nonlocal calls
+        calls += 1
+
+        return val
+
+    coros = [coro() for _ in range(100)]
+    ret = await asyncio.gather(*coros)
+    expected = [val] * 100
+    assert ret == expected
+    check_lru(coro, hits=99, misses=1, cache=1, tasks=0)
+
+    assert calls == 1
+    assert await coro() is val
+    check_lru(coro, hits=100, misses=1, cache=1, tasks=0)
+
+
+@pytest.mark.asyncio
+async def test_alru_cache_dict_not_shared(check_lru, loop):
+    async def coro(val):
+        return val
+
+    coro1 = alru_cache()(coro)
+    coro2 = alru_cache()(coro)
+
+    ret1 = await coro1(1)
+    check_lru(coro1, hits=0, misses=1, cache=1, tasks=0)
+
+    ret2 = await coro2(1)
+    check_lru(coro2, hits=0, misses=1, cache=1, tasks=0)
+
+    assert ret1 == ret2
+
+    assert coro1._cache[1].result() == coro2._cache[1].result()
+    assert coro1._cache != coro2._cache
+    assert coro1._cache.keys() == coro2._cache.keys()
+    assert coro1._cache is not coro2._cache
diff --git a/tests/external/test_cache_clear.py b/tests/external/test_cache_clear.py
new file mode 100644
index 0000000..4e59ea6
--- /dev/null
+++ b/tests/external/test_cache_clear.py
@@ -0,0 +1,22 @@
+import asyncio
+
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_cache_clear(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        return val
+
+    inputs = [1, 2, 3]
+    coros = [coro(v) for v in inputs]
+    ret = await asyncio.gather(*coros)
+    assert ret == inputs
+    check_lru(coro, hits=0, misses=3, cache=3, tasks=0)
+
+    coro.cache_clear()
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
diff --git a/tests/external/test_cache_info.py b/tests/external/test_cache_info.py
new file mode 100644
index 0000000..1a39b96
--- /dev/null
+++ b/tests/external/test_cache_info.py
@@ -0,0 +1,38 @@
+import asyncio
+
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_cache_info(check_lru, loop):
+    @alru_cache(maxsize=4)
+    async def coro(val):
+        return val
+
+    inputs = [1, 2, 3]
+    coros = [coro(v) for v in inputs]
+    ret = await asyncio.gather(*coros)
+    assert ret == inputs
+    check_lru(coro, hits=0, misses=3, cache=3, tasks=0, maxsize=4)
+
+    coro.cache_clear()
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0, maxsize=4)
+
+    inputs = [1, 1, 1]
+    coros = [coro(v) for v in inputs]
+    ret = await asyncio.gather(*coros)
+    assert ret == inputs
+    check_lru(coro, hits=2, misses=1, cache=1, tasks=0, maxsize=4)
+
+    coro.cache_clear()
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0, maxsize=4)
+
+    inputs = [1, 2, 3, 4] * 2
+    coros = [coro(v) for v in inputs]
+    ret = await asyncio.gather(*coros)
+    assert ret == inputs
+    check_lru(coro, hits=4, misses=4, cache=4, tasks=0, maxsize=4)
diff --git a/tests/external/test_cache_invalidate.py b/tests/external/test_cache_invalidate.py
new file mode 100644
index 0000000..48dfd8c
--- /dev/null
+++ b/tests/external/test_cache_invalidate.py
@@ -0,0 +1,85 @@
+import asyncio
+
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_cache_invalidate(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        return val
+
+    inputs = [1, 2, 3]
+
+    coro.invalidate(1)
+    coro.invalidate(2)
+    coro.invalidate(3)
+
+    coros = [coro(v) for v in inputs]
+
+    ret = await asyncio.gather(*coros)
+
+    assert ret == inputs
+    check_lru(coro, hits=0, misses=3, cache=3, tasks=0)
+
+    coro.invalidate(1)
+    check_lru(coro, hits=0, misses=3, cache=2, tasks=0)
+    coro.invalidate(2)
+    check_lru(coro, hits=0, misses=3, cache=1, tasks=0)
+    coro.invalidate(3)
+    check_lru(coro, hits=0, misses=3, cache=0, tasks=0)
+
+    inputs = [1, 2, 3]
+    coros = [coro(v) for v in inputs]
+
+    ret = await asyncio.gather(*coros)
+
+    assert ret == inputs
+    check_lru(coro, hits=0, misses=6, cache=3, tasks=0)
+
+
+async def test_cache_invalidate_multiple_args(check_lru, loop):
+    @alru_cache()
+    async def coro(*args):
+        return len(args)
+
+    for i, size in enumerate(range(10)):
+        args = tuple(range(size))
+        ret = await coro(*args)
+        assert ret == size
+        check_lru(coro, hits=0, misses=i + 1, cache=1, tasks=0)
+        coro.invalidate(*args)
+        check_lru(coro, hits=0, misses=i + 1, cache=0, tasks=0)
+
+    for size in range(10):
+        args = tuple(range(size))
+        ret = await coro(*args)
+        assert ret == size
+    check_lru(coro, hits=0, misses=20, cache=10, tasks=0)
+
+
+async def test_cache_invalidate_multiple_args_different_order(check_lru, loop):
+    @alru_cache()
+    async def coro(*args):
+        return len(args)
+
+    for i, size in enumerate(range(2, 10)):
+        args = tuple(range(size))
+        rev_args = tuple(reversed(args))
+        ret = await coro(*args)
+        assert ret == size
+        check_lru(coro, hits=0, misses=2 * i + 1, cache=i + 1, tasks=0)
+        ret = await coro(*rev_args)
+        # The reversed args should be a miss
+        check_lru(coro, hits=0, misses=2 * i + 2, cache=i + 2, tasks=0)
+        coro.invalidate(*rev_args)
+        # The reversed args should be invalidated
+        check_lru(coro, hits=0, misses=2 * i + 2, cache=i + 1, tasks=0)
+
+    for i, size in enumerate(range(2, 10)):
+        args = tuple(range(size))
+        ret = await coro(*args)
+        assert ret == size
+        check_lru(coro, hits=i + 1, misses=16, cache=8, tasks=0)
diff --git a/tests/external/test_close.py b/tests/external/test_close.py
new file mode 100644
index 0000000..3008899
--- /dev/null
+++ b/tests/external/test_close.py
@@ -0,0 +1,170 @@
+import asyncio
+
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_cache_close(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        await asyncio.sleep(0.2)
+
+        return val
+
+    assert not coro.closed
+
+    inputs = [1, 2, 3, 4, 5]
+
+    coros = [coro(v) for v in inputs]
+
+    gather = asyncio.gather(*coros)
+
+    await asyncio.sleep(0.1)
+
+    check_lru(coro, hits=0, misses=5, cache=5, tasks=5)
+
+    close = coro.close()
+
+    with pytest.raises(RuntimeError):
+        await coro(1)
+
+    check_lru(coro, hits=0, misses=5, cache=5, tasks=5)
+
+    ret_close = await close
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    ret_gather = await gather
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    assert set(ret_close) == set(ret_gather) == set(inputs)
+
+    with pytest.raises(RuntimeError):
+        coro.close()
+
+
+async def test_cache_close_cancel_return_exceptions(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        await asyncio.sleep(0.2)
+
+        return val
+
+    inputs = [1, 2, 3, 4, 5]
+
+    coros = [coro(v) for v in inputs]
+
+    gather = asyncio.gather(*coros)
+
+    await asyncio.sleep(0.1)
+
+    close = coro.close(cancel=True)
+
+    check_lru(coro, hits=0, misses=5, cache=5, tasks=5)
+
+    ret_close = await close
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    for err in ret_close:
+        assert isinstance(err, asyncio.CancelledError)
+
+    with pytest.raises(asyncio.CancelledError):
+        await gather
+
+
+async def test_cache_close_cancel_not_return_exceptions(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        await asyncio.sleep(0.2)
+
+        return val
+
+    inputs = [1, 2, 3, 4, 5]
+
+    coros = [coro(v) for v in inputs]
+
+    gather = asyncio.gather(*coros)
+
+    await asyncio.sleep(0.1)
+
+    close = coro.close(cancel=True, return_exceptions=False)
+
+    check_lru(coro, hits=0, misses=5, cache=5, tasks=5)
+
+    with pytest.raises(asyncio.CancelledError):
+        await close
+
+    with pytest.raises(asyncio.CancelledError):
+        await gather
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+
+async def test_cache_close_return_exceptions(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        await asyncio.sleep(0.2)
+
+        raise ZeroDivisionError
+
+    inputs = [1, 2, 3, 4, 5]
+
+    coros = [coro(v) for v in inputs]
+
+    gather = asyncio.gather(*coros)
+
+    await asyncio.sleep(0.1)
+
+    close = coro.close()
+
+    check_lru(coro, hits=0, misses=5, cache=5, tasks=5)
+
+    with pytest.raises(ZeroDivisionError):
+        await gather
+
+    check_lru(coro, hits=0, misses=5, cache=5, tasks=0)
+
+    ret_close = await close
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    for err in ret_close:
+        assert isinstance(err, ZeroDivisionError)
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+
+async def test_cache_close_not_return_exceptions(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        await asyncio.sleep(0.2)
+
+        raise ZeroDivisionError
+
+    inputs = [1, 2, 3, 4, 5]
+
+    coros = [coro(v) for v in inputs]
+
+    gather = asyncio.gather(*coros, return_exceptions=True)
+
+    await asyncio.sleep(0.1)
+
+    close = coro.close(return_exceptions=False)
+
+    check_lru(coro, hits=0, misses=5, cache=5, tasks=5)
+
+    with pytest.raises(ZeroDivisionError):
+        await close
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    ret_gather = await gather
+
+    for err in ret_gather:
+        assert isinstance(err, ZeroDivisionError)
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
diff --git a/tests/external/test_exception.py b/tests/external/test_exception.py
new file mode 100644
index 0000000..3d4aa25
--- /dev/null
+++ b/tests/external/test_exception.py
@@ -0,0 +1,48 @@
+import asyncio
+
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_alru_cache_exception(check_lru, loop):
+    @alru_cache(cache_exceptions=True)
+    async def coro(val):
+        1 / 0
+
+    inputs = [1, 1, 1]
+    coros = [coro(v) for v in inputs]
+
+    ret = await asyncio.gather(*coros, return_exceptions=True)
+
+    check_lru(coro, hits=2, misses=1, cache=1, tasks=0)
+
+    for item in ret:
+        assert isinstance(item, ZeroDivisionError)
+
+    with pytest.raises(ZeroDivisionError):
+        await coro(1)
+
+    check_lru(coro, hits=3, misses=1, cache=1, tasks=0)
+
+
+async def test_alru_not_cache_exception(check_lru, loop):
+    @alru_cache(cache_exceptions=False)
+    async def coro(val):
+        1 / 0
+
+    inputs = [1, 1, 1]
+    coros = [coro(v) for v in inputs]
+
+    ret = await asyncio.gather(*coros, return_exceptions=True)
+
+    check_lru(coro, hits=2, misses=1, cache=1, tasks=0)
+
+    for item in ret:
+        assert isinstance(item, ZeroDivisionError)
+
+    with pytest.raises(ZeroDivisionError):
+        await coro(1)
+
+    check_lru(coro, hits=2, misses=2, cache=1, tasks=0)
diff --git a/tests/external/test_internals.py b/tests/external/test_internals.py
new file mode 100644
index 0000000..1003bff
--- /dev/null
+++ b/tests/external/test_internals.py
@@ -0,0 +1,366 @@
+import asyncio
+from collections import OrderedDict
+from functools import _make_key, partial
+from unittest import mock
+
+import pytest
+from great_ai.external.async_lru import (
+    __cache_touch,
+    _cache_clear,
+    _cache_hit,
+    _cache_info,
+    _cache_invalidate,
+    _cache_miss,
+    _close,
+    _close_waited,
+    _done_callback,
+    _open,
+    _wait_closed,
+)
+
+
+class Wrapped:
+    pass
+
+
+@pytest.mark.asyncio
+async def test_done_callback_cancelled(loop):
+    task = loop.create_future()
+    fut = loop.create_future()
+
+    task.add_done_callback(partial(_done_callback, fut))
+
+    task.cancel()
+
+    await asyncio.sleep(0)
+
+    assert fut.cancelled()
+
+
+@pytest.mark.asyncio
+async def test_done_callback_exception(loop):
+    task = loop.create_future()
+    fut = loop.create_future()
+
+    task.add_done_callback(partial(_done_callback, fut))
+
+    exc = ZeroDivisionError()
+
+    task.set_exception(exc)
+
+    await asyncio.sleep(0)
+
+    with pytest.raises(ZeroDivisionError):
+        await fut
+
+    with pytest.raises(ZeroDivisionError):
+        fut.result()
+
+    assert fut.exception() is exc
+
+
+@pytest.mark.asyncio
+async def test_done_callback(loop):
+    task = loop.create_future()
+    fut = loop.create_future()
+
+    task.add_done_callback(partial(_done_callback, fut))
+
+    task.set_result(1)
+
+    await asyncio.sleep(0)
+
+    assert fut.result() == 1
+
+
+def test_cache_invalidate_typed():
+    wrapped = Wrapped()
+    wrapped._cache = {}
+
+    args = (1,)
+    kwargs = {"1": 1}
+
+    from_cache = _cache_invalidate(wrapped, True, *args, **kwargs)
+
+    assert not from_cache
+
+    key = _make_key(args, kwargs, True)
+
+    wrapped._cache[key] = 0
+
+    from_cache = _cache_invalidate(wrapped, True, *args, **kwargs)
+
+    assert from_cache
+
+    assert len(wrapped._cache) == 0
+
+    wrapped._cache[key] = 0
+
+    args = (1.0,)
+
+    from_cache = _cache_invalidate(wrapped, True, *args, **kwargs)
+
+    assert not from_cache
+
+    wrapped._cache[key] = 1
+
+
+def test_cache_invalidate_not_typed():
+    wrapped = Wrapped()
+    wrapped._cache = {}
+
+    args = (1,)
+    kwargs = {"1": 1}
+
+    from_cache = _cache_invalidate(wrapped, False, *args, **kwargs)
+
+    assert not from_cache
+
+    key = _make_key(args, kwargs, False)
+
+    wrapped._cache[key] = 0
+
+    from_cache = _cache_invalidate(wrapped, False, *args, **kwargs)
+
+    assert from_cache
+
+    assert len(wrapped._cache) == 0
+
+    wrapped._cache[key] = 0
+
+    args = (1.0,)
+
+    from_cache = _cache_invalidate(wrapped, False, *args, **kwargs)
+
+    assert from_cache
+
+    assert len(wrapped._cache) == 0
+
+
+def test_cache_clear():
+    wrapped = Wrapped()
+
+    attrs = ["hits", "_cache", "tasks"]
+    for attr in attrs:
+        assert not hasattr(wrapped, attr)
+
+    _cache_clear(wrapped)
+
+    for attr in attrs:
+        assert hasattr(wrapped, attr)
+
+    assert wrapped.hits == wrapped.misses == 0
+    assert isinstance(wrapped._cache, dict)
+    assert len(wrapped._cache) == 0
+    assert isinstance(wrapped.tasks, set)
+    assert len(wrapped.tasks) == 0
+
+    _cache = wrapped._cache
+    tasks = wrapped.tasks
+
+    _cache_clear(wrapped)
+
+    assert wrapped._cache is not _cache
+    assert wrapped.tasks is not tasks
+
+
+def test_open():
+    wrapped = Wrapped()
+    wrapped.hits = wrapped.misses = 1
+    wrapped._cache = {}
+    wrapped.tasks = set()
+    wrapped.closed = True
+
+    with pytest.raises(RuntimeError):
+        _open(wrapped)
+
+    wrapped.hits = wrapped.misses = 0
+
+    _open(wrapped)
+
+    assert not wrapped.closed
+
+    with pytest.raises(RuntimeError):
+        _open(wrapped)
+
+
+def test_close(loop):
+    wrapped = Wrapped()
+    wrapped.closed = False
+    wrapped.tasks = set()
+
+    awaitable = _close(wrapped, cancel=False, return_exceptions=True)
+    loop.run_until_complete(awaitable)
+
+    assert wrapped.closed
+
+    with pytest.raises(RuntimeError):
+        _close(wrapped, cancel=False, return_exceptions=True)
+
+    fut = loop.create_future()
+    wrapped.closed = False
+    wrapped.tasks = {fut}
+
+    awaitable = _close(wrapped, cancel=True, return_exceptions=True)
+    loop.run_until_complete(awaitable)
+
+    assert fut.cancelled()
+
+    fut = loop.create_future()
+    fut.set_result(None)
+    wrapped.closed = False
+    wrapped.tasks = {fut}
+
+    awaitable = _close(wrapped, cancel=True, return_exceptions=True)
+    loop.run_until_complete(awaitable)
+
+    assert not fut.cancelled()
+
+    fut = loop.create_future()
+    fut.set_exception(ZeroDivisionError)
+    wrapped.closed = False
+    wrapped.tasks = {fut}
+
+    awaitable = _close(wrapped, cancel=True, return_exceptions=True)
+    loop.run_until_complete(awaitable)
+
+    assert not fut.cancelled()
+
+
+@pytest.mark.asyncio
+async def test_wait_closed(loop):
+    wrapped = Wrapped()
+    wrapped.tasks = set()
+
+    with mock.patch("great_ai.external.async_lru._close_waited") as mocked:
+        ret = await _wait_closed(
+            wrapped,
+            return_exceptions=True,
+        )
+        assert ret == []
+        assert mocked.called_once()
+
+    asyncio.set_event_loop(loop)
+    with mock.patch("great_ai.external.async_lru._close_waited") as mocked:
+        ret = await _wait_closed(
+            wrapped,
+            return_exceptions=True,
+        )
+        assert ret == []
+        assert mocked.called_once()
+    asyncio.set_event_loop(None)
+
+    fut = loop.create_future()
+    fut.set_result(None)
+    wrapped.tasks = {fut}
+    with mock.patch("great_ai.external.async_lru._close_waited") as mocked:
+        ret = await _wait_closed(
+            wrapped,
+            return_exceptions=True,
+        )
+        assert ret == [None]
+        assert mocked.called_once()
+
+    exc = ZeroDivisionError()
+    fut = loop.create_future()
+    fut.set_exception(exc)
+    wrapped.tasks = {fut}
+    with mock.patch("great_ai.external.async_lru._close_waited") as mocked:
+        ret = await _wait_closed(
+            wrapped,
+            return_exceptions=True,
+        )
+        assert ret == [exc]
+        assert mocked.called_once()
+
+    fut = loop.create_future()
+    fut.set_exception(ZeroDivisionError)
+    wrapped.tasks = {fut}
+    with mock.patch("great_ai.external.async_lru._close_waited") as mocked:
+        with pytest.raises(ZeroDivisionError):
+            await _wait_closed(
+                wrapped,
+                return_exceptions=False,
+            )
+        assert mocked.called_once()
+
+
+def test_close_waited():
+    wrapped = Wrapped()
+    wrapped.cache_clear = partial(_cache_clear, wrapped)
+
+    with mock.patch("great_ai.external.async_lru._cache_clear") as mocked:
+        _close_waited(wrapped, None)
+
+        assert mocked.called_once()
+
+
+def test_cache_info():
+    wrapped = Wrapped()
+    wrapped._cache = {}
+    wrapped.hits = wrapped.misses = 0
+
+    assert (0, 0, 3, 0) == _cache_info(wrapped, 3)
+
+    wrapped._cache[1] = 1
+
+    assert (0, 0, 1, 1) == _cache_info(wrapped, 1)
+
+    wrapped.hits = 2
+    wrapped.misses = 3
+    wrapped._cache[2] = 2
+
+    assert (2, 3, 5, 2) == _cache_info(wrapped, 5)
+
+
+def test__cache_touch():
+    wrapped = Wrapped()
+
+    wrapped._cache = OrderedDict()
+    wrapped._cache[1] = 1
+    wrapped._cache[2] = 2
+
+    __cache_touch(wrapped, 1)
+    assert list(wrapped._cache) == [2, 1]
+
+    __cache_touch(wrapped, 2)
+    assert list(wrapped._cache) == [1, 2]
+
+    # test KeyError
+    __cache_touch(wrapped, 100)
+
+
+def test_cache_hit():
+    wrapped = Wrapped()
+    wrapped.hits = 1
+    wrapped._cache = OrderedDict()
+    wrapped._cache[1] = 1
+
+    with mock.patch("great_ai.external.async_lru.__cache_touch") as mocked:
+        _cache_hit(wrapped, 1)
+
+        assert mocked.called_once()
+
+    assert wrapped.hits == 2
+
+    _cache_hit(wrapped, 1)
+
+    assert wrapped.hits == 3
+
+
+def test_cache_miss():
+    wrapped = Wrapped()
+    wrapped.misses = 1
+    wrapped._cache = OrderedDict()
+    wrapped._cache[1] = 1
+
+    with mock.patch("great_ai.external.async_lru.__cache_touch") as mocked:
+        _cache_miss(wrapped, 1)
+
+        assert mocked.called_once()
+
+    assert wrapped.misses == 2
+
+    _cache_miss(wrapped, 1)
+
+    assert wrapped.misses == 3
diff --git a/tests/external/test_open.py b/tests/external/test_open.py
new file mode 100644
index 0000000..b749df4
--- /dev/null
+++ b/tests/external/test_open.py
@@ -0,0 +1,39 @@
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_alru_cache_open(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        return val
+
+    await coro(1)
+
+    check_lru(coro, hits=0, misses=1, cache=1, tasks=0)
+
+    with pytest.raises(RuntimeError):
+        coro.open()
+
+    close = coro.close()
+
+    assert coro.closed
+
+    with pytest.raises(RuntimeError):
+        await coro()
+
+    with pytest.raises(RuntimeError):
+        coro.open()
+
+    await close
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    coro.open()
+
+    ret = await coro(1)
+
+    assert ret == 1
+
+    check_lru(coro, hits=0, misses=1, cache=1, tasks=0)
diff --git a/tests/external/test_partialmethod.py b/tests/external/test_partialmethod.py
new file mode 100644
index 0000000..dfa888f
--- /dev/null
+++ b/tests/external/test_partialmethod.py
@@ -0,0 +1,50 @@
+import asyncio
+from functools import partial, partialmethod
+
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_partialmethod_basic(check_lru, loop):
+    class Obj:
+        async def _coro(self, val):
+            return val
+
+        coro = alru_cache(partialmethod(_coro, 2))
+
+    obj = Obj()
+
+    coros = [obj.coro() for _ in range(5)]
+
+    check_lru(obj.coro, hits=0, misses=0, cache=0, tasks=0)
+
+    ret = await asyncio.gather(*coros)
+
+    check_lru(obj.coro, hits=4, misses=1, cache=1, tasks=0)
+
+    assert ret == [2, 2, 2, 2, 2]
+
+
+async def test_partialmethod_partial(check_lru, loop):
+    class Obj:
+        def __init__(self):
+            self.coro = alru_cache(partial(self._coro, 2))
+
+        async def __coro(self, val1, val2):
+            return val1 + val2
+
+        _coro = partialmethod(__coro, 1)
+
+    obj = Obj()
+
+    coros = [obj.coro() for _ in range(5)]
+
+    check_lru(obj.coro, hits=0, misses=0, cache=0, tasks=0)
+
+    ret = await asyncio.gather(*coros)
+
+    check_lru(obj.coro, hits=4, misses=1, cache=1, tasks=0)
+
+    assert ret == [3, 3, 3, 3, 3]
diff --git a/tests/external/test_size.py b/tests/external/test_size.py
new file mode 100644
index 0000000..c683c8e
--- /dev/null
+++ b/tests/external/test_size.py
@@ -0,0 +1,58 @@
+import asyncio
+
+import pytest
+from great_ai.external.async_lru import _make_key, alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_alru_cache_removing_lru_keys(check_lru, loop):
+    @alru_cache(maxsize=3)
+    async def coro(val):
+        return val
+
+    key5 = _make_key((5,), {}, False)
+    key4 = _make_key((4,), {}, False)
+    key3 = _make_key((3,), {}, False)
+    key2 = _make_key((2,), {}, False)
+    key1 = _make_key((1,), {}, False)
+
+    for i, v in enumerate([3, 4, 5]):
+        await coro(v)
+        check_lru(coro, hits=0, misses=i + 1, cache=i + 1, tasks=0, maxsize=3)
+
+    check_lru(coro, hits=0, misses=3, cache=3, tasks=0, maxsize=3)
+    assert list(coro._cache) == [key3, key4, key5]
+
+    for v in [3, 2, 1]:
+        await coro(v)
+    check_lru(coro, hits=1, misses=5, cache=3, tasks=0, maxsize=3)
+    assert list(coro._cache) == [key3, key2, key1]
+
+
+async def test_alru_cache_none_max_size(check_lru, loop):
+    @alru_cache(maxsize=None)
+    async def coro(val):
+        return val
+
+    inputs = [1, 2, 3, 4] * 2
+    coros = [coro(v) for v in inputs]
+
+    ret = await asyncio.gather(*coros)
+
+    check_lru(coro, hits=4, misses=4, cache=4, tasks=0, maxsize=None)
+    assert ret == inputs
+
+
+async def test_alru_cache_zero_max_size(check_lru, loop):
+    @alru_cache(maxsize=0)
+    async def coro(val):
+        return val
+
+    inputs = [1, 2, 3, 4] * 2
+    coros = [coro(v) for v in inputs]
+
+    ret = await asyncio.gather(*coros)
+
+    check_lru(coro, hits=0, misses=8, cache=0, tasks=0, maxsize=0)
+    assert ret == inputs
diff --git a/tests/external/test_utils.py b/tests/external/test_utils.py
new file mode 100644
index 0000000..aa52d5d
--- /dev/null
+++ b/tests/external/test_utils.py
@@ -0,0 +1,19 @@
+from functools import partial
+
+from great_ai.external.async_lru import unpartial
+
+
+def test_unpartial():
+    def foo():
+        pass
+
+    assert unpartial(foo) is foo
+
+    bar = partial(foo)
+
+    assert unpartial(bar) is foo
+
+    for _ in range(10):
+        bar = partial(bar)
+
+    assert unpartial(bar) is foo