vfdev-5: @sdesrozis we now again start to receive coverage reports. We need to workout codecov/patch...
sdesrozis: Ok, I can add tests to cover uncovered code at the moment 😉 
diff --git a/ignite/metrics/metric.py b/ignite/metrics/metric.py
index c3146d05..645f1ddc 100644
--- a/ignite/metrics/metric.py
+++ b/ignite/metrics/metric.py
@@ -58,6 +58,8 @@ class EpochWise(MetricUsage):
     - :meth:`~ignite.metrics.Metric.completed` on every :attr:`~ignite.engine.Events.EPOCH_COMPLETED`.
     """
 
+    usage_name = "epoch_wise"
+
     def __init__(self):
         super(EpochWise, self).__init__(
             started=Events.EPOCH_STARTED,
@@ -77,6 +79,8 @@ class BatchWise(MetricUsage):
     - :meth:`~ignite.metrics.Metric.completed` on every :attr:`~ignite.engine.Events.ITERATION_COMPLETED`.
     """
 
+    usage_name = "batch_wise"
+
     def __init__(self):
         super(BatchWise, self).__init__(
             started=Events.ITERATION_STARTED,
@@ -266,12 +270,14 @@ class Metric(metaclass=ABCMeta):
 
     def _check_usage(self, usage: Union[str, MetricUsage]) -> MetricUsage:
         if isinstance(usage, str):
-            if usage == "epoch_wise":
+            if usage == EpochWise.usage_name:
                 usage = EpochWise()
-            elif usage == "batch_wise":
+            elif usage == BatchWise.usage_name:
                 usage = BatchWise()
             else:
-                raise ValueError("usage should be 'epoch_wise' or 'batch_wise', get {}".format(usage))
+                raise ValueError(
+                    "usage should be 'EpochWise.usage_name' or 'BatchWise.usage_name', get {}".format(usage)
+                )
         if not isinstance(usage, MetricUsage):
             raise TypeError("Unhandled usage type {}".format(type(usage)))
         return usage
@@ -285,7 +291,7 @@ class Metric(metaclass=ABCMeta):
             engine (Engine): the engine to which the metric must be attached
             name (str): the name of the metric to attach
             usage (str or MetricUsage, optional): the usage of the metric. Valid string values should be
-                'epoch_wise' (default) or 'batch_wise'.
+                'EpochWise.usage_name' (default) or 'BatchWise.usage_name'.
 
         Example:
 
@@ -303,11 +309,11 @@ class Metric(metaclass=ABCMeta):
         .. code-block:: python
 
             metric = ...
-            metric.attach(engine, "mymetric", usage="batch_wise")
+            metric.attach(engine, "mymetric", usage=BatchWise.usage_name)
 
             assert "mymetric" in engine.run(data).metrics
 
-            assert metric.is_attached(engine, usage="batch_wise")
+            assert metric.is_attached(engine, usage=BatchWise.usage_name)
         """
         usage = self._check_usage(usage)
         if not engine.has_event_handler(self.started, usage.STARTED):

Add usage name in MetricUsage
## 🚀 Feature

Following @ericspod comment, usage name should be embedded in usage classes.

```python
class EpochWise(MetricUsage):
    usage_name = "epoch_wise"
    ...
```

https://github.com/pytorch/ignite/pull/1018#issuecomment-630506840
diff --git a/tests/ignite/metrics/test_metric.py b/tests/ignite/metrics/test_metric.py
index 89def6b6..50c5d428 100644
--- a/tests/ignite/metrics/test_metric.py
+++ b/tests/ignite/metrics/test_metric.py
@@ -11,7 +11,7 @@ from sklearn.metrics import confusion_matrix, f1_score, precision_score, recall_
 
 from ignite.engine import Engine, Events, State
 from ignite.metrics import ConfusionMatrix, Precision, Recall
-from ignite.metrics.metric import BatchFiltered, Metric, reinit__is_reduced
+from ignite.metrics.metric import BatchFiltered, BatchWise, EpochWise, Metric, reinit__is_reduced
 
 
 class DummyMetric1(Metric):
@@ -667,6 +667,51 @@ def test_completed():
     assert engine.state.metrics == {"metric": "foo"}
 
 
+def test_usage_exception():
+    engine = Engine(lambda e, b: b)
+    m = DummyMetric2()
+    with pytest.raises(TypeError, match=r"Unhandled usage type"):
+        m.attach(engine, "dummy", usage=1)
+    with pytest.raises(ValueError, match=r"usage should be 'EpochWise.usage_name' or 'BatchWise.usage_name'"):
+        m.attach(engine, "dummy", usage="fake")
+
+
+def test_epochwise_usage():
+    class MyMetric(Metric):
+        def __init__(self):
+            super(MyMetric, self).__init__()
+            self.value = []
+
+        def reset(self):
+            self.value = []
+
+        def compute(self):
+            return self.value
+
+        def update(self, output):
+            self.value.append(output)
+
+    def test(usage):
+        engine = Engine(lambda e, b: b)
+
+        m = MyMetric()
+
+        m.attach(engine, "ewm", usage=usage)
+
+        @engine.on(Events.EPOCH_COMPLETED)
+        def _():
+            ewm = engine.state.metrics["ewm"]
+            assert len(ewm) == 3
+            assert ewm == [0, 1, 2]
+
+        engine.run([0, 1, 2], max_epochs=10)
+        m.detach(engine, usage=usage)
+
+    test("epoch_wise")
+    test(EpochWise.usage_name)
+    test(EpochWise())
+
+
 def test_batchwise_usage():
     class MyMetric(Metric):
         def __init__(self):
@@ -682,19 +727,25 @@ def test_batchwise_usage():
         def update(self, output):
             self.value.append(output)
 
-    engine = Engine(lambda e, b: b)
+    def test(usage):
+        engine = Engine(lambda e, b: b)
 
-    m = MyMetric()
+        m = MyMetric()
 
-    m.attach(engine, "bwm", usage="batch_wise")
+        m.attach(engine, "bwm", usage=usage)
 
-    @engine.on(Events.ITERATION_COMPLETED)
-    def _():
-        bwm = engine.state.metrics["bwm"]
-        assert len(bwm) == 1
-        assert bwm[0] == (engine.state.iteration - 1) % 3
+        @engine.on(Events.ITERATION_COMPLETED)
+        def _():
+            bwm = engine.state.metrics["bwm"]
+            assert len(bwm) == 1
+            assert bwm[0] == (engine.state.iteration - 1) % 3
+
+        engine.run([0, 1, 2], max_epochs=10)
+        m.detach(engine, usage=usage)
 
-    engine.run([0, 1, 2], max_epochs=10)
+    test("batch_wise")
+    test(BatchWise.usage_name)
+    test(BatchWise())
 
 
 def test_batchfiltered_usage():

pip install -e .
parse_log_pytest
requirements.txt
pytest
apt-get update apt-get install -y gcc pip install torch torchvision -f https://download.pytorch.org/whl/cpu/torch_stable.html -U
3.7
requirements-dev.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
absl-py==2.1.0
alembic==1.12.1
arrow==1.2.3
attrs==24.2.0
boto3==1.33.13
botocore==1.33.13
bravado==11.1.0
bravado-core==6.1.1
cached-property==1.5.2
cachetools==5.5.2
certifi @ file:///croot/certifi_1671487769961/work/certifi
charset-normalizer==3.4.1
click==7.1.2
cloudpickle==2.2.1
codecov==2.1.13
coverage==7.2.7
cycler==0.11.0
databricks-cli==0.18.0
dill==0.3.7
docker==6.1.3
entrypoints==0.4
exceptiongroup==1.2.2
execnet==2.0.2
Flask==1.1.4
fonttools==4.38.0
fqdn==1.5.1
funcsigs==1.0.2
furl==2.1.4
future==1.0.0
gitdb==4.0.12
GitPython==3.1.44
google-auth==2.38.0
google-auth-oauthlib==0.4.6
greenlet==3.1.1
grpcio==1.62.3
gunicorn==20.1.0
gym==0.26.2
gym-notices==0.0.8
hestia==0.6.0
humanfriendly==10.0
idna==3.10
importlib-metadata==5.2.0
importlib-resources==5.12.0
iniconfig==2.0.0
isoduration==20.11.0
itsdangerous==1.1.0
Jinja2==2.10.3
jmespath==1.0.1
joblib==1.3.2
jsonpatch==1.33
jsonpointer==3.0.0
jsonref==1.1.0
jsonschema==4.17.3
kiwisolver==1.4.5
Mako==1.2.4
Markdown==3.4.4
MarkupSafe==2.1.5
marshmallow==3.0.0rc5
matplotlib==3.5.3
mlflow==1.30.1
monotonic==1.6
msgpack==1.0.5
neptune-client==1.11.1
networkx==2.6.3
numpy==1.21.6
oauthlib==3.2.2
orderedmultidict==1.0.1
packaging==21.3
pandas==1.3.5
pathlib2==2.3.7.post1
Pillow==9.5.0
pkgutil_resolve_name==1.3.10
pluggy==1.2.0
polyaxon-client==0.6.1
polyaxon-schemas==0.6.1
polystores==0.2.5
prometheus-client==0.17.1
prometheus_flask_exporter==0.23.2
protobuf==3.20.3
psutil==7.0.0
pyasn1==0.5.1
pyasn1-modules==0.3.0
PyJWT==2.8.0
pynvml==11.5.3
pyparsing==3.1.4
pyrsistent==0.19.3
pytest==7.4.4
pytest-cov==4.1.0
pytest-xdist==3.5.0
python-dateutil==2.9.0.post0
-e git+https://github.com/pytorch/ignite.git@3afba87b647d099ef9bb377309f8103a65d9e6ca#egg=pytorch_ignite
pytz==2022.7.1
PyYAML==6.0.1
querystring-parser==1.2.4
requests==2.31.0
requests-file==2.1.0
requests-oauthlib==2.0.0
requests-toolbelt==1.0.0
rfc3339-validator==0.1.4
rfc3986-validator==0.1.1
rhea==0.5.5
rsa==4.9
s3transfer==0.8.2
scikit-learn==1.0.2
scipy==1.7.3
simplejson==3.20.1
six==1.17.0
smmap==5.0.2
SQLAlchemy==1.4.54
sqlparse==0.4.4
swagger-spec-validator==3.0.3
tabulate==0.9.0
tensorboard==2.11.2
tensorboard-data-server==0.6.1
tensorboard-plugin-wit==1.8.1
tensorboardX==2.6.2.2
threadpoolctl==3.1.0
tomli==2.0.1
torch==1.13.1+cpu
torchvision==0.14.1+cpu
tornado==6.2
tqdm==4.67.1
trains==0.16.4
typing_extensions==4.7.1
uri-template==1.3.0
urllib3==1.26.20
visdom==0.2.4
webcolors==1.13
websocket-client==1.6.1
Werkzeug==1.0.1
zipp==3.15.0

name: ignite
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2022.12.7=py37h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.4.4=h6a678d5_1
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - pip=22.3.1=py37h06a4308_0
  - python=3.7.16=h7a1cb2a_0
  - readline=8.2=h5eee18b_0
  - setuptools=65.6.3=py37h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.38.4=py37h06a4308_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - absl-py==2.1.0
      - alembic==1.12.1
      - arrow==1.2.3
      - attrs==24.2.0
      - boto3==1.33.13
      - botocore==1.33.13
      - bravado==11.1.0
      - bravado-core==6.1.1
      - cached-property==1.5.2
      - cachetools==5.5.2
      - charset-normalizer==3.4.1
      - click==7.1.2
      - cloudpickle==2.2.1
      - codecov==2.1.13
      - coverage==7.2.7
      - cycler==0.11.0
      - databricks-cli==0.18.0
      - dill==0.3.7
      - docker==6.1.3
      - entrypoints==0.4
      - exceptiongroup==1.2.2
      - execnet==2.0.2
      - flask==1.1.4
      - fonttools==4.38.0
      - fqdn==1.5.1
      - funcsigs==1.0.2
      - furl==2.1.4
      - future==1.0.0
      - gitdb==4.0.12
      - gitpython==3.1.44
      - google-auth==2.38.0
      - google-auth-oauthlib==0.4.6
      - greenlet==3.1.1
      - grpcio==1.62.3
      - gunicorn==20.1.0
      - gym==0.26.2
      - gym-notices==0.0.8
      - hestia==0.6.0
      - humanfriendly==10.0
      - idna==3.10
      - importlib-metadata==5.2.0
      - importlib-resources==5.12.0
      - iniconfig==2.0.0
      - isoduration==20.11.0
      - itsdangerous==1.1.0
      - jinja2==2.10.3
      - jmespath==1.0.1
      - joblib==1.3.2
      - jsonpatch==1.33
      - jsonpointer==3.0.0
      - jsonref==1.1.0
      - jsonschema==4.17.3
      - kiwisolver==1.4.5
      - mako==1.2.4
      - markdown==3.4.4
      - markupsafe==2.1.5
      - marshmallow==3.0.0rc5
      - matplotlib==3.5.3
      - mlflow==1.30.1
      - monotonic==1.6
      - msgpack==1.0.5
      - neptune-client==1.11.1
      - networkx==2.6.3
      - numpy==1.21.6
      - oauthlib==3.2.2
      - orderedmultidict==1.0.1
      - packaging==21.3
      - pandas==1.3.5
      - pathlib2==2.3.7.post1
      - pillow==9.5.0
      - pkgutil-resolve-name==1.3.10
      - pluggy==1.2.0
      - polyaxon-client==0.6.1
      - polyaxon-schemas==0.6.1
      - polystores==0.2.5
      - prometheus-client==0.17.1
      - prometheus-flask-exporter==0.23.2
      - protobuf==3.20.3
      - psutil==7.0.0
      - pyasn1==0.5.1
      - pyasn1-modules==0.3.0
      - pyjwt==2.8.0
      - pynvml==11.5.3
      - pyparsing==3.1.4
      - pyrsistent==0.19.3
      - pytest==7.4.4
      - pytest-cov==4.1.0
      - pytest-xdist==3.5.0
      - python-dateutil==2.9.0.post0
      - pytorch-ignite==0.4.0
      - pytz==2022.7.1
      - pyyaml==6.0.1
      - querystring-parser==1.2.4
      - requests==2.31.0
      - requests-file==2.1.0
      - requests-oauthlib==2.0.0
      - requests-toolbelt==1.0.0
      - rfc3339-validator==0.1.4
      - rfc3986-validator==0.1.1
      - rhea==0.5.5
      - rsa==4.9
      - s3transfer==0.8.2
      - scikit-learn==1.0.2
      - scipy==1.7.3
      - simplejson==3.20.1
      - six==1.17.0
      - smmap==5.0.2
      - sqlalchemy==1.4.54
      - sqlparse==0.4.4
      - swagger-spec-validator==3.0.3
      - tabulate==0.9.0
      - tensorboard==2.11.2
      - tensorboard-data-server==0.6.1
      - tensorboard-plugin-wit==1.8.1
      - tensorboardx==2.6.2.2
      - threadpoolctl==3.1.0
      - tomli==2.0.1
      - torch==1.13.1+cpu
      - torchvision==0.14.1+cpu
      - tornado==6.2
      - tqdm==4.67.1
      - trains==0.16.4
      - typing-extensions==4.7.1
      - uri-template==1.3.0
      - urllib3==1.26.20
      - visdom==0.2.4
      - webcolors==1.13
      - websocket-client==1.6.1
      - werkzeug==1.0.1
      - zipp==3.15.0
prefix: /opt/conda/envs/ignite

tests/ignite/metrics/test_metric.py::test_usage_exception tests/ignite/metrics/test_metric.py::test_epochwise_usage tests/ignite/metrics/test_metric.py::test_batchwise_usage
tests/ignite/metrics/test_metric.py::test_no_transform tests/ignite/metrics/test_metric.py::test_transform tests/ignite/metrics/test_metric.py::test_output_as_mapping_wrong_keys tests/ignite/metrics/test_metric.py::test_output_as_mapping_keys_is_none tests/ignite/metrics/test_metric.py::test_output_as_mapping tests/ignite/metrics/test_metric.py::test_no_grad tests/ignite/metrics/test_metric.py::test_arithmetics tests/ignite/metrics/test_metric.py::test_attach tests/ignite/metrics/test_metric.py::test_detach tests/ignite/metrics/test_metric.py::test_integration tests/ignite/metrics/test_metric.py::test_abstract_class tests/ignite/metrics/test_metric.py::test_pytorch_operators tests/ignite/metrics/test_metric.py::test_indexing_metric tests/ignite/metrics/test_metric.py::test__sync_all_reduce tests/ignite/metrics/test_metric.py::test_distrib_cpu tests/ignite/metrics/test_metric.py::test_completed tests/ignite/metrics/test_metric.py::test_batchfiltered_usage
ignite/metrics/metric.py
ignite/metrics/metric.py