diff --git a/.gitignore b/.gitignore
index cbd36b4c..79aeec4d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 env/
+.hypothesis/
 .mypy_cache/
 .pytest_cache/
 __pycache__/
diff --git a/a_sync/exceptions.py b/a_sync/exceptions.py
index 172f8801..30ee7276 100644
--- a/a_sync/exceptions.py
+++ b/a_sync/exceptions.py
@@ -66,3 +66,7 @@ def __init__(self):
         err = f"The event loop is already running, which means you're trying to use an ASync function synchronously from within an async context.\n"
         err += f"Check your traceback to determine which, then try calling asynchronously instead with one of the following kwargs:\n"
         err += f"{_flags.VIABLE_FLAGS}"
+
+class MappingNotEmptyError(Exception):
+    def __init__(self):
+        super().__init__("TaskMapping already contains some data. In order to use `map`, you need a fresh one.")
diff --git a/a_sync/task.py b/a_sync/task.py
index 90f283f9..073645bd 100644
--- a/a_sync/task.py
+++ b/a_sync/task.py
@@ -2,8 +2,8 @@
 import asyncio
 import logging
 
-from a_sync._typing import K, P, T, V
 from a_sync._typing import *
+from a_sync import exceptions
 from a_sync.utils.iterators import as_yielded
 from a_sync.utils.as_completed import as_completed
 
@@ -37,13 +37,14 @@ def __getitem__(self, item: K) -> "asyncio.Task[V]":
             super().__setitem__(item, task)
             return task
     async def map(self, *iterables: AnyIterable[K], pop: bool = True, yields: Literal['keys', 'both'] = 'both') -> AsyncIterator[Tuple[K, V]]:
-        assert not self, "must be empty"
-        async for key in as_yielded(*[__yield_keys(iterable) for iterable in iterables]):  # type: ignore [attr-defined]
+        if self:
+            raise exceptions.MappingNotEmptyError
+        async for key in as_yielded(*[_yield_keys(iterable) for iterable in iterables]):  # type: ignore [attr-defined]
             self[key]  # ensure task is running
             async for key, value in self.yield_completed(pop=pop):
-                yield __yield(key, value, yields)
+                yield _yield(key, value, yields)
         async for key, value in as_completed(self, aiter=True):
-            yield __yield(key, value, yields)
+            yield _yield(key, value, yields)
     async def yield_completed(self, pop: bool = True) -> AsyncIterator[Tuple[K, V]]:
         for k, task in dict(self).items():
             if task.done():
@@ -69,15 +70,19 @@ def __prune_persisted_tasks():
                 raise e
             __persisted_tasks.discard(task)
 
-def __yield(key: Any, value: Any, yields: Literal['keys', 'both']):
+@overload
+def _yield(key: K, value: V, yields: Literal['keys']) -> K:...
+@overload
+def _yield(key: K, value: V, yields: Literal['both']) -> Tuple[K, V]:...
+def _yield(key: K, value: V, yields: Literal['keys', 'both']) -> Union[K, Tuple[K, V]]:
     if yields == 'both':
-        yield key, value
+        return key, value
     elif yields == 'keys':
-        yield key
+        return key
     else:
         raise ValueError(f"`yields` must be 'keys' or 'both'. You passed {yields}")
 
-async def __yield_keys(iterable: AnyIterable[K]) -> AsyncIterator[K]:
+async def _yield_keys(iterable: AnyIterable[K]) -> AsyncIterator[K]:
     if isinstance(iterable, AsyncIterable):
         async for key in iterable:
             yield key
diff --git a/tests/test_task.py b/tests/test_task.py
index 61149985..71b183d0 100644
--- a/tests/test_task.py
+++ b/tests/test_task.py
@@ -1,7 +1,7 @@
 import asyncio
 import pytest
 
-from a_sync import create_task
+from a_sync import TaskMapping, create_task, exceptions
 
 @pytest.mark.asyncio_cooperative
 async def test_create_task():
@@ -27,3 +27,58 @@ async def task():
     await asyncio.sleep(0)
     # previously, it failed here
     create_task(coro=task(), skip_gc_until_done=True)
+
+@pytest.mark.asyncio_cooperative
+async def test_task_mapping_init():
+    tasks = TaskMapping(_coro_fn)
+    assert tasks._coro_fn is _coro_fn
+    assert tasks._coro_fn_kwargs == {}
+    assert tasks._name == ""
+    tasks = TaskMapping(_coro_fn, name='test', kwarg0=1, kwarg1=None)
+    assert tasks._coro_fn_kwargs == {'kwarg0': 1, 'kwarg1': None}
+    assert tasks._name == "test"
+
+@pytest.mark.asyncio_cooperative
+async def test_task_mapping():
+    tasks = TaskMapping(_coro_fn)
+    # does it return the correct type
+    assert isinstance(tasks[0], asyncio.Task)
+    # does it correctly return existing values
+    assert tasks[1] is tasks[1]
+    # does the task return the correct value
+    assert await tasks[0] == "1"
+    # can it do it again
+    assert await tasks[0] == "1"
+    
+@pytest.mark.asyncio_cooperative
+async def test_task_mapping_map_with_sync_iter():
+    tasks = TaskMapping(_coro_fn)
+    async for k, v in tasks.map(range(5)):
+        assert isinstance(k, int)
+        assert isinstance(v, str)
+    with pytest.raises(exceptions.MappingNotEmptyError):
+        async for k in tasks.map(range(5), yields='keys'):
+            assert isinstance(k, int)
+    tasks = TaskMapping(_coro_fn)
+    async for k in tasks.map(range(5), yields='keys'):
+        assert isinstance(k, int)
+    
+@pytest.mark.asyncio_cooperative
+async def test_task_mapping_map_with_async_iter():
+    async def async_iter():
+        for i in range(5):
+            yield i
+    tasks = TaskMapping(_coro_fn)
+    async for k, v in tasks.map(async_iter()):
+        assert isinstance(k, int)
+        assert isinstance(v, str)
+    with pytest.raises(exceptions.MappingNotEmptyError):
+        async for k in tasks.map(async_iter(), yields='keys'):
+            assert isinstance(k, int)
+    tasks = TaskMapping(_coro_fn)
+    async for k in tasks.map(async_iter(), yields='keys'):
+        assert isinstance(k, int)
+
+async def _coro_fn(i: int) -> str:
+    i += 1
+    return str(i) * i
\ No newline at end of file