diff --git a/royalnet/engineer/blueprints/blueprint.py b/royalnet/engineer/blueprints/blueprint.py
index 70b47634..66a60f31 100644
--- a/royalnet/engineer/blueprints/blueprint.py
+++ b/royalnet/engineer/blueprints/blueprint.py
@@ -63,7 +63,7 @@ class Blueprint(metaclass=abc.ABCMeta):
         .. code-block::
 
             def print_msg(message: Message):
-                message.requires(Message.text, Message.timestamp)
+                message.requires("text", "timestamp")
                 print(f"{message.timestamp().isoformat()}: {message.text()}")
 
         :raises .exc.NeverAvailableError: If at least one of the fields raised a :exc:`.exc.NeverAvailableError`.
@@ -75,7 +75,7 @@ class Blueprint(metaclass=abc.ABCMeta):
 
         for field in fields:
             try:
-                field(self)
+                self.__getattribute__(field)()
             except exc.NeverAvailableError as ex:
                 exceptions.append(ex)
             except exc.NotAvailableError as ex:
diff --git a/royalnet/engineer/sentry/filter.py b/royalnet/engineer/sentry/filter.py
index 173fb363..200a20b8 100644
--- a/royalnet/engineer/sentry/filter.py
+++ b/royalnet/engineer/sentry/filter.py
@@ -8,7 +8,7 @@ from royalnet.royaltyping import *
 import functools
 import logging
 
-from engineer import exc, blueprints
+from .. import exc, blueprints
 
 log = logging.getLogger(__name__)
 
@@ -155,7 +155,7 @@ class Filter:
         - the :class:`.blueprints.Blueprint` never has data for at least one of the fields,
           :exc:`.exc.NotAvailableError` is propagated upwards.
 
-        :param fields: The fields to test for.
+        :param fields: The fields to test for, as strings.
         :param propagate_not_available: If :exc:`.exc.NotAvailableError` should be propagated
                                         instead of discarding the errored object.
         :param propagate_never_available: If :exc:`.exc.NeverAvailableError` should be propagated
@@ -166,11 +166,11 @@ class Filter:
             try:
                 return obj.requires(*fields)
             except exc.NotAvailableError:
-                if not propagate_not_available:
+                if propagate_not_available:
                     raise
                 raise exc.Discard(obj, "Data is not available")
             except exc.NeverAvailableError:
-                if not propagate_never_available:
+                if propagate_never_available:
                     raise
                 raise exc.Discard(obj, "Data is never available")
 
diff --git a/royalnet/engineer/tests/test_sentry.py b/royalnet/engineer/tests/test_sentry.py
index a875cea0..47363fb4 100644
--- a/royalnet/engineer/tests/test_sentry.py
+++ b/royalnet/engineer/tests/test_sentry.py
@@ -2,7 +2,7 @@ import pytest
 import asyncio
 import async_timeout
 import re
-from .. import sentry, exc, blueprints
+from royalnet.engineer import sentry, exc, blueprints
 
 
 @pytest.fixture
@@ -82,6 +82,7 @@ class TestFilter:
     async def test_filter(self, s: sentry.Sentry):
         await s.queue.put(None)
         await s.queue.put(None)
+        await s.queue.put(None)
 
         assert await s.f().filter(lambda x: x is None, "Is not None").get_single() is None
 
@@ -147,28 +148,24 @@ class TestFilter:
                 return 3
 
         avmsg = AvailableMessage()
-        namsg = NotAvailableMessage()
-        nvmsg = NeverAvailableMessage()
-
         await s.queue.put(avmsg)
-        await s.queue.put(namsg)
-        await s.queue.put(nvmsg)
-        await s.queue.put(namsg)
-        await s.queue.put(nvmsg)
-
-        assert await s.f().requires(blueprints.Message.text).get_single() is avmsg
+        assert await s.f().requires("text").get_single() is avmsg
 
+        await s.queue.put(NotAvailableMessage())
         with pytest.raises(exc.Discard):
-            await s.f().requires(blueprints.Message.text).get_single()
+            await s.f().requires("text").get_single()
 
+        await s.queue.put(NeverAvailableMessage())
         with pytest.raises(exc.NeverAvailableError):
-            await s.f().requires(blueprints.Message.text).get_single()
+            await s.f().requires("text").get_single()
 
+        await s.queue.put(NotAvailableMessage())
         with pytest.raises(exc.NotAvailableError):
-            await s.f().requires(blueprints.Message.text, propagate_not_available=True).get_single()
+            await s.f().requires("text", propagate_not_available=True).get_single()
 
+        await s.queue.put(NeverAvailableMessage())
         with pytest.raises(exc.Discard):
-            await s.f().requires(blueprints.Message.text, propagate_never_available=False).get_single()
+            await s.f().requires("text", propagate_never_available=False).get_single()
 
     @pytest.mark.asyncio
     async def test_startswith(self, s: sentry.Sentry):
diff --git a/royalnet/tests/test_pytest.py b/royalnet/tests/test_pytest.py
new file mode 100644
index 00000000..0b43ce3d
--- /dev/null
+++ b/royalnet/tests/test_pytest.py
@@ -0,0 +1,14 @@
+import asyncio
+import pytest
+
+
+async def sleep_and_raise():
+    await asyncio.sleep(0.001)
+    raise Exception("Please except this gift!")
+
+
+@pytest.mark.asyncio
+class TestAsyncio:
+    async def test_exception(self):
+        with pytest.raises(Exception):
+            await sleep_and_raise()