diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 6598f91..a739691 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -1,10 +1,12 @@
 name: Lint
+permissions:
+  contents: read
 
 on:
   pull_request:
 
 jobs:
-  lint:
+  flake8:
     runs-on: ubuntu-latest
 
     steps:
@@ -15,4 +17,26 @@ jobs:
       - uses: TrueBrain/actions-flake8@v2
         with:
           flake8_version: 6.0.0
-          plugins: flake8-isort==6.1.1 flake8-quotes==3.4.0
+          plugins: flake8-isort==6.1.1 flake8-quotes==3.4.0 flake8-commas==4.0.0
+
+  mypy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: 3.9
+
+      - run: |
+          pip install poetry
+          poetry install --with=mypy -E all
+
+      - run: |
+          poetry run mypy \
+            --check-untyped-defs \
+            --disable-error-code=import-untyped \
+            --strict-equality \
+            --warn-redundant-casts \
+            --warn-unused-ignores \
+            mandible
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 7436549..f3ab535 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -1,4 +1,6 @@
 name: Test
+permissions:
+  contents: read
 
 on:
   push:
diff --git a/mandible/metadata_mapper/builder.py b/mandible/metadata_mapper/builder.py
index 90a6d58..509b645 100644
--- a/mandible/metadata_mapper/builder.py
+++ b/mandible/metadata_mapper/builder.py
@@ -103,7 +103,7 @@ def mapped(
     directive_name = Mapped.directive_name
     assert directive_name is not None
 
-    params = {
+    params: dict[str, Any] = {
         "source": source,
         "key": key,
     }
diff --git a/mandible/metadata_mapper/directive/reformatted.py b/mandible/metadata_mapper/directive/reformatted.py
index 593b9f2..49cd7f0 100644
--- a/mandible/metadata_mapper/directive/reformatted.py
+++ b/mandible/metadata_mapper/directive/reformatted.py
@@ -4,8 +4,9 @@
 
 from mandible.metadata_mapper.exception import MetadataMapperError
 from mandible.metadata_mapper.format import FORMAT_REGISTRY
+from mandible.metadata_mapper.types import Key
 
-from .directive import Key, TemplateDirective, get_key
+from .directive import TemplateDirective, get_key
 
 
 @dataclass
diff --git a/mandible/metadata_mapper/exception.py b/mandible/metadata_mapper/exception.py
index f4d9ccc..5878b35 100644
--- a/mandible/metadata_mapper/exception.py
+++ b/mandible/metadata_mapper/exception.py
@@ -1,3 +1,6 @@
+from typing import Optional
+
+
 class MetadataMapperError(Exception):
     """A generic error raised by the MetadataMapper"""
 
@@ -8,7 +11,7 @@ def __init__(self, msg: str):
 class TemplateError(MetadataMapperError):
     """An error that occurred while processing the metadata template."""
 
-    def __init__(self, msg: str, debug_path: str = None):
+    def __init__(self, msg: str, debug_path: Optional[str] = None):
         super().__init__(msg)
         self.debug_path = debug_path
 
@@ -26,7 +29,7 @@ class ContextValueError(MetadataMapperError):
     def __init__(
         self,
         msg: str,
-        source_name: str = None,
+        source_name: Optional[str] = None,
     ):
         super().__init__(msg)
         self.source_name = source_name
diff --git a/mandible/metadata_mapper/format/__init__.py b/mandible/metadata_mapper/format/__init__.py
index b57a46c..0f3899d 100644
--- a/mandible/metadata_mapper/format/__init__.py
+++ b/mandible/metadata_mapper/format/__init__.py
@@ -11,12 +11,12 @@
 try:
     from .h5 import H5
 except ImportError:
-    from .format import H5
+    from .format import H5  # type: ignore
 
 try:
     from .xml import Xml
 except ImportError:
-    from .format import Xml
+    from .format import Xml  # type: ignore
 
 
 __all__ = (
diff --git a/mandible/metadata_mapper/format/format.py b/mandible/metadata_mapper/format/format.py
index cda2cb1..168853d 100644
--- a/mandible/metadata_mapper/format/format.py
+++ b/mandible/metadata_mapper/format/format.py
@@ -1,11 +1,12 @@
 import contextlib
+import inspect
 import json
 import re
 import zipfile
 from abc import ABC, abstractmethod
-from collections.abc import Iterable
+from collections.abc import Generator, Iterable
 from dataclasses import dataclass
-from typing import IO, Any, TypeVar
+from typing import IO, Any, Generic, TypeVar
 
 from mandible import jsonpath
 from mandible.metadata_mapper.key import RAISE_EXCEPTION, Key
@@ -50,7 +51,7 @@ def get_value(self, file: IO[bytes], key: Key) -> Any:
 
 
 @dataclass
-class FileFormat(Format, ABC, register=False):
+class FileFormat(Format, Generic[T], ABC, register=False):
     """A Format for querying files from a standard data file.
 
     Simple, single format data types such as 'json' that can be queried
@@ -76,7 +77,7 @@ def get_value(self, file: IO[bytes], key: Key) -> Any:
         with self.parse_data(file) as data:
             return self._eval_key_wrapper(data, key)
 
-    def _eval_key_wrapper(self, data, key: Key) -> Any:
+    def _eval_key_wrapper(self, data: T, key: Key) -> Any:
         try:
             return self.eval_key(data, key)
         except KeyError as e:
@@ -116,7 +117,7 @@ def eval_key(data: T, key: Key) -> Any:
 
 
 @dataclass
-class _PlaceholderBase(FileFormat, register=False):
+class _PlaceholderBase(FileFormat[None], register=False):
     """
     Base class for defining placeholder implementations for classes that
     require extra dependencies to be installed
@@ -124,16 +125,18 @@ class _PlaceholderBase(FileFormat, register=False):
     def __init__(self, dep: str):
         raise Exception(
             f"{dep} must be installed to use the {self.__class__.__name__} "
-            "format class"
+            "format class",
         )
 
     @staticmethod
-    def parse_data(file: IO[bytes]) -> contextlib.AbstractContextManager[T]:
-        pass
+    def parse_data(file: IO[bytes]) -> contextlib.AbstractContextManager[None]:
+        # __init__ always raises
+        raise RuntimeError("Unreachable!")
 
     @staticmethod
-    def eval_key(data: T, key: Key):
-        pass
+    def eval_key(data: None, key: Key):
+        # __init__ always raises
+        raise RuntimeError("Unreachable!")
 
 
 @dataclass
@@ -151,10 +154,10 @@ def __init__(self):
 # Define formats that don't require extra dependencies
 
 @dataclass
-class Json(FileFormat):
+class Json(FileFormat[dict]):
     @staticmethod
     @contextlib.contextmanager
-    def parse_data(file: IO[bytes]) -> dict:
+    def parse_data(file: IO[bytes]) -> Generator[dict]:
         yield json.load(file)
 
     @staticmethod
@@ -237,20 +240,26 @@ def _matches_filters(self, zipinfo: zipfile.ZipInfo) -> bool:
         return True
 
 
+ZIP_INFO_ATTRS = [
+    name
+    for name, _ in inspect.getmembers(zipfile.ZipInfo, inspect.isdatadescriptor)
+    if not name.startswith("_")
+]
+
+
 @dataclass
-class ZipInfo(FileFormat):
+class ZipInfo(FileFormat[dict]):
     """Query Zip headers and directory information."""
 
     @staticmethod
     @contextlib.contextmanager
-    def parse_data(file: IO[bytes]) -> dict:
+    def parse_data(file: IO[bytes]) -> Generator[dict]:
         with zipfile.ZipFile(file, "r") as zf:
             yield {
                 "infolist": [
                     {
                         k: getattr(info, k)
-                        for k in info.__slots__
-                        if not k.startswith("_")
+                        for k in ZIP_INFO_ATTRS
                     }
                     for info in zf.infolist()
                 ],
diff --git a/mandible/metadata_mapper/format/h5.py b/mandible/metadata_mapper/format/h5.py
index ac2365b..6ebce94 100644
--- a/mandible/metadata_mapper/format/h5.py
+++ b/mandible/metadata_mapper/format/h5.py
@@ -11,13 +11,13 @@
 
 
 @dataclass
-class H5(FileFormat):
+class H5(FileFormat[Any]):
     @staticmethod
     def parse_data(file: IO[bytes]) -> contextlib.AbstractContextManager[Any]:
         return h5py.File(file, "r")
 
     @staticmethod
-    def eval_key(data, key: Key) -> Any:
+    def eval_key(data: Any, key: Key) -> Any:
         return normalize(data[key.key][()])
 
 
diff --git a/mandible/metadata_mapper/format/xml.py b/mandible/metadata_mapper/format/xml.py
index 1dbee9f..3e09af2 100644
--- a/mandible/metadata_mapper/format/xml.py
+++ b/mandible/metadata_mapper/format/xml.py
@@ -1,6 +1,7 @@
 import contextlib
+from collections.abc import Generator, Iterable
 from dataclasses import dataclass
-from typing import IO, Any
+from typing import IO, Any, Union
 
 from lxml import etree
 
@@ -10,16 +11,34 @@
 
 
 @dataclass
-class Xml(FileFormat):
+class Xml(FileFormat[etree._ElementTree]):
     @staticmethod
     @contextlib.contextmanager
-    def parse_data(file: IO[bytes]) -> Any:
+    def parse_data(file: IO[bytes]) -> Generator[etree._ElementTree]:
         yield etree.parse(file)
 
     @staticmethod
-    def eval_key(data: etree.ElementTree, key: Key) -> Any:
+    def eval_key(data: etree._ElementTree, key: Key) -> Any:
         nsmap = data.getroot().nsmap
-        elements = data.xpath(key.key, namespaces=nsmap)
-        values = [element.text for element in elements]
+        xpath_result = data.xpath(
+            key.key,
+            # Lxml type stubs don't handle None key for default namespaces
+            namespaces=nsmap,  # type: ignore
+        )
+        if isinstance(xpath_result, Iterable):
+            values = [convert_result(item) for item in xpath_result]
 
-        return key.resolve_list_match(values)
+            return key.resolve_list_match(values)
+
+        # Xpath supports functions such as `count` that can result in
+        # `data.xpath` returning something other than a list of matches.
+        return xpath_result
+
+
+def convert_result(result: Union[etree._Element, int, str, bytes, tuple]):
+    if isinstance(result, etree._Element):
+        return result.text
+    if isinstance(result, (int, str, bytes)):
+        return result
+
+    raise TypeError(f"Unsupported type {repr(result.__class__.__name__)}")
diff --git a/mandible/metadata_mapper/mapper.py b/mandible/metadata_mapper/mapper.py
index 7f71d0e..d198d0a 100644
--- a/mandible/metadata_mapper/mapper.py
+++ b/mandible/metadata_mapper/mapper.py
@@ -16,7 +16,7 @@ class MetadataMapper:
     def __init__(
         self,
         template: Template,
-        source_provider: SourceProvider = None,
+        source_provider: Optional[SourceProvider] = None,
         *,
         directive_marker: str = "@",
     ):
@@ -48,7 +48,7 @@ def get_metadata(self, context: Context) -> Template:
             raise
         except Exception as e:
             raise MetadataMapperError(
-                f"failed to cache source keys: {e}"
+                f"failed to cache source keys: {e}",
             ) from e
 
         for name, source in sources.items():
@@ -66,21 +66,22 @@ def get_metadata(self, context: Context) -> Template:
             raise
         except Exception as e:
             raise MetadataMapperError(
-                f"failed to evaluate template: {e}"
+                f"failed to evaluate template: {e}",
             ) from e
 
     def _prepare_directives(self, context: Context, sources: dict[str, Source]):
         for value, debug_path in _walk_values(self.template):
             if isinstance(value, dict):
-                directive_name = self._get_directive_name(value, debug_path)
-                if directive_name is None:
+                directive_config = self._get_directive_name(value, debug_path)
+                if directive_config is None:
                     continue
 
+                directive_name, directive_body = directive_config
                 directive = self._get_directive(
                     directive_name,
                     context,
                     sources,
-                    value[directive_name],
+                    directive_body,
                     f"{debug_path}.{directive_name}",
                 )
                 directive.prepare()
@@ -91,13 +92,14 @@ def _replace_template(
         template: Template,
         sources: dict[str, Source],
         debug_path: str = "$",
-    ):
+    ) -> Template:
         if isinstance(template, dict):
-            directive_name = self._get_directive_name(
+            directive_config = self._get_directive_name(
                 template,
-                debug_path
+                debug_path,
             )
-            if directive_name is not None:
+            if directive_config is not None:
+                directive_name, directive_body = directive_config
                 debug_path = f"{debug_path}.{directive_name}"
                 directive = self._get_directive(
                     directive_name,
@@ -110,15 +112,15 @@ def _replace_template(
                             sources,
                             debug_path=f"{debug_path}.{k}",
                         )
-                        for k, v in template[directive_name].items()
+                        for k, v in directive_body.items()
                     },
-                    debug_path
+                    debug_path,
                 )
                 try:
                     return directive.call()
                 except Exception as e:
                     raise MetadataMapperError(
-                        f"failed to call directive at {debug_path}: {e}"
+                        f"failed to call directive at {debug_path}: {e}",
                     ) from e
 
             return {
@@ -146,38 +148,48 @@ def _replace_template(
 
     def _get_directive_name(
         self,
-        value: dict,
+        value: dict[str, Template],
         debug_path: str,
-    ) -> Optional[str]:
-        directive_names = [
-            key for key in value
-            if key.startswith(self.directive_marker)
+    ) -> Optional[tuple[str, dict[str, Template]]]:
+        directive_configs = [
+            (k, v)
+            for (k, v) in value.items()
+            if k.startswith(self.directive_marker)
         ]
-        if not directive_names:
+        if not directive_configs:
             return None
 
-        if len(directive_names) > 1:
+        if len(directive_configs) > 1:
             raise TemplateError(
                 "multiple directives found in config: "
-                f"{', '.join(repr(d) for d in directive_names)}",
-                debug_path
+                f"{', '.join(repr(k) for k, v in directive_configs)}",
+                debug_path,
+            )
+
+        directive_name, directive_config = directive_configs[0]
+
+        if not isinstance(directive_config, dict):
+            raise TemplateError(
+                "directive body should be type 'dict' not "
+                f"{repr(directive_config.__class__.__name__)}",
+                f"{debug_path}.{directive_name}",
             )
 
-        return directive_names[0]
+        return directive_name, directive_config
 
     def _get_directive(
         self,
         directive_name: str,
         context: Context,
         sources: dict[str, Source],
-        config: dict,
+        config: dict[str, Template],
         debug_path: str,
     ) -> TemplateDirective:
         cls = DIRECTIVE_REGISTRY.get(directive_name[len(self.directive_marker):])
         if cls is None:
             raise TemplateError(
                 f"invalid directive {repr(directive_name)}",
-                debug_path
+                debug_path,
             )
 
         argspec = inspect.getfullargspec(cls.__init__)
@@ -186,7 +198,7 @@ def _get_directive(
         required_keys = set(
             argspec.args[3:-len(argspec.defaults)]
             if argspec.defaults else
-            argspec.args[3:]
+            argspec.args[3:],
         )
         config_keys = set(config.keys())
         diff = required_keys - config_keys
@@ -198,7 +210,7 @@ def _get_directive(
             raise TemplateError(
                 f"missing key{s}: "
                 f"{', '.join(repr(d) for d in sorted(diff))}",
-                debug_path
+                debug_path,
             )
 
         # For forward compatibility, ignore any unexpected keys
diff --git a/mandible/metadata_mapper/source.py b/mandible/metadata_mapper/source.py
index f702996..acbe500 100644
--- a/mandible/metadata_mapper/source.py
+++ b/mandible/metadata_mapper/source.py
@@ -55,6 +55,6 @@ def query_all_values(self, context: Context):
                 "%s: using keys %r, got new values %r",
                 self,
                 keys,
-                new_values
+                new_values,
             )
             self._values.update(new_values)
diff --git a/mandible/metadata_mapper/source_provider.py b/mandible/metadata_mapper/source_provider.py
index a32accf..cb76c0d 100644
--- a/mandible/metadata_mapper/source_provider.py
+++ b/mandible/metadata_mapper/source_provider.py
@@ -11,7 +11,7 @@
 
 T = TypeVar("T")
 
-REGISTRY_TYPE_MAP = {
+REGISTRY_TYPE_MAP: dict[str, dict[str, Any]] = {
     "Format": FORMAT_REGISTRY,
     "Source": SOURCE_REGISTRY,
     "Storage": STORAGE_REGISTRY,
@@ -72,7 +72,7 @@ def _create_object(
         cls_name = config.get("class")
         if cls_name is None:
             raise SourceProviderError(
-                f"missing key 'class' in config {config}"
+                f"missing key 'class' in config {config}",
             )
 
         # TODO(reweeden): As of python3.10, inspect.get_annotations(parent_cls)
diff --git a/mandible/metadata_mapper/storage/__init__.py b/mandible/metadata_mapper/storage/__init__.py
index 298866a..cee45fe 100644
--- a/mandible/metadata_mapper/storage/__init__.py
+++ b/mandible/metadata_mapper/storage/__init__.py
@@ -11,12 +11,12 @@
 try:
     from .cmr_query import CmrQuery
 except ImportError:
-    from .storage import CmrQuery
+    from .storage import CmrQuery  # type: ignore
 
 try:
     from .http_request import HttpRequest
 except ImportError:
-    from .storage import HttpRequest
+    from .storage import HttpRequest  # type: ignore
 
 
 __all__ = (
diff --git a/mandible/metadata_mapper/storage/cmr_query.py b/mandible/metadata_mapper/storage/cmr_query.py
index 9f80605..d5d95bf 100644
--- a/mandible/metadata_mapper/storage/cmr_query.py
+++ b/mandible/metadata_mapper/storage/cmr_query.py
@@ -18,7 +18,7 @@ class CmrQuery(HttpRequest):
     format: str = ""
     token: Optional[str] = None
 
-    def __post_init__(self, url: str):
+    def __post_init__(self, url: Optional[str]):
         if url:
             raise ValueError(
                 "do not set 'url' directly, use 'base_url' and 'path' instead",
diff --git a/mandible/metadata_mapper/storage/storage.py b/mandible/metadata_mapper/storage/storage.py
index a6854ae..1ea69e4 100644
--- a/mandible/metadata_mapper/storage/storage.py
+++ b/mandible/metadata_mapper/storage/storage.py
@@ -43,11 +43,12 @@ class _PlaceholderBase(Storage, register=False):
     def __init__(self, dep: str):
         raise Exception(
             f"{dep} must be installed to use the {self.__class__.__name__} "
-            "format class"
+            "format class",
         )
 
     def open_file(self, context: Context) -> IO[bytes]:
-        pass
+        # __init__ always raises
+        raise RuntimeError("Unreachable!")
 
 
 @dataclass
diff --git a/mandible/umm_classes/base.py b/mandible/umm_classes/base.py
index 235b2da..0e7fd34 100644
--- a/mandible/umm_classes/base.py
+++ b/mandible/umm_classes/base.py
@@ -111,7 +111,7 @@ def get_umm_date_time_format(self) -> str:
     def related_urls_files_sort_key(self, file: CMAGranuleFile) -> tuple:
         type_order = self.get_related_url_type_order()
         try:
-            type_ordinal = type_order.index(file.get("type"))
+            type_ordinal = type_order.index(file.get("type", "data"))
         except ValueError:
             type_ordinal = len(type_order)
 
diff --git a/pyproject.toml b/pyproject.toml
index d3fe048..b788cec 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -42,6 +42,11 @@ pytest = "^8.0.2"
 pytest-cov = "^4.0.0"
 pytest-mock = "^3.8.2"
 
+[tool.poetry.group.mypy.dependencies]
+lxml-stubs = "^0.5.1"
+mypy = "^1.14.1"
+types-requests = "<2.31.0.7"
+
 
 [tool.pytest.ini_options]
 markers = [
diff --git a/tests/integration_tests/test_metadata_mapper.py b/tests/integration_tests/test_metadata_mapper.py
index ca01498..94521a5 100644
--- a/tests/integration_tests/test_metadata_mapper.py
+++ b/tests/integration_tests/test_metadata_mapper.py
@@ -287,6 +287,26 @@ def test_invalid_directive(context):
         mapper.get_metadata(context)
 
 
+def test_invalid_directive_config_type(context):
+    mapper = MetadataMapper(
+        template={
+            "foo": {
+                "@mapped": 100,
+            },
+        },
+        source_provider=ConfigSourceProvider({}),
+    )
+
+    with pytest.raises(
+        MetadataMapperError,
+        match=(
+            r"failed to process template at \$\.foo\.@mapped: "
+            "directive body should be type 'dict' not 'int'"
+        ),
+    ):
+        mapper.get_metadata(context)
+
+
 def test_multiple_directives(context):
     mapper = MetadataMapper(
         template={
diff --git a/tests/test_format.py b/tests/test_format.py
index 58a6db4..1e69d31 100644
--- a/tests/test_format.py
+++ b/tests/test_format.py
@@ -310,6 +310,7 @@ def test_xml():
             Key("./nested/qux"),
             Key("./list/v", return_list=True),
             Key("./list/v", return_first=True),
+            Key("count(./list/v)"),
         ],
     ) == {
         Key("/root/foo"): "foo value",
@@ -318,6 +319,7 @@ def test_xml():
         Key("./nested/qux"): "qux nested value",
         Key("./list/v", return_list=True): ["list", "value"],
         Key("./list/v", return_first=True): "list",
+        Key("count(./list/v)"): 2,
     }
 
 
diff --git a/tests/test_source_provider.py b/tests/test_source_provider.py
index 888639d..5b3e404 100644
--- a/tests/test_source_provider.py
+++ b/tests/test_source_provider.py
@@ -56,23 +56,23 @@ def test_config_source_provider(sources):
             "storage": {
                 "class": "LocalFile",
                 "filters": {
-                    "name": "foo"
-                }
+                    "name": "foo",
+                },
             },
             "format": {
-                "class": "Json"
-            }
+                "class": "Json",
+            },
         },
         "bar": {
             "storage": {
                 "class": "LocalFile",
                 "filters": {
-                    "name": "bar"
-                }
+                    "name": "bar",
+                },
             },
             "format": {
-                "class": "Json"
-            }
+                "class": "Json",
+            },
         },
         "baz": {
             "storage": {
@@ -145,35 +145,35 @@ def test_config_source_provider_all_formats():
             "storage": {
                 "class": "LocalFile",
                 "filters": {
-                    "name": "foo"
-                }
+                    "name": "foo",
+                },
             },
             "format": {
-                "class": "Json"
-            }
+                "class": "Json",
+            },
         },
         "xml": {
             "storage": {
                 "class": "LocalFile",
                 "filters": {
-                    "name": "bar"
-                }
+                    "name": "bar",
+                },
             },
             "format": {
-                "class": "Xml"
-            }
+                "class": "Xml",
+            },
         },
         "h5": {
             "storage": {
                 "class": "LocalFile",
                 "filters": {
-                    "name": "baz"
-                }
+                    "name": "baz",
+                },
             },
             "format": {
-                "class": "H5"
-            }
-        }
+                "class": "H5",
+            },
+        },
     })
 
     assert provider.get_sources() == {
@@ -237,9 +237,9 @@ def test_config_source_provider_missing_storage():
     provider = ConfigSourceProvider({
         "source": {
             "format": {
-                "class": "Json"
-            }
-        }
+                "class": "Json",
+            },
+        },
     })
 
     with pytest.raises(
@@ -256,9 +256,9 @@ def test_config_source_provider_invalid_storage():
     provider = ConfigSourceProvider({
         "source": {
             "storage": {
-                "class": "NotARealStorage"
-            }
-        }
+                "class": "NotARealStorage",
+            },
+        },
     })
 
     with pytest.raises(
@@ -266,7 +266,7 @@ def test_config_source_provider_invalid_storage():
         match=(
             "failed to create source 'source': "
             "invalid storage type 'NotARealStorage'"
-        )
+        ),
     ):
         provider.get_sources()
 
@@ -277,9 +277,9 @@ def test_config_source_provider_invalid_storage_kwargs(cls_name):
         "source": {
             "storage": {
                 "class": cls_name,
-                "invalid_arg": 1
-            }
-        }
+                "invalid_arg": 1,
+            },
+        },
     })
 
     with pytest.raises(
@@ -288,7 +288,7 @@ def test_config_source_provider_invalid_storage_kwargs(cls_name):
             "failed to create source 'source': "
             rf"({cls_name}\.)?__init__\(\) got an unexpected keyword argument "
             "'invalid_arg'"
-        )
+        ),
     ):
         provider.get_sources()
 
@@ -297,9 +297,9 @@ def test_config_source_provider_missing_format():
     provider = ConfigSourceProvider({
         "source": {
             "storage": {
-                "class": "S3File"
-            }
-        }
+                "class": "S3File",
+            },
+        },
     })
 
     with pytest.raises(
@@ -316,12 +316,12 @@ def test_config_source_provider_invalid_format():
     provider = ConfigSourceProvider({
         "source": {
             "storage": {
-                "class": "S3File"
+                "class": "S3File",
             },
             "format": {
-                "class": "NotARealFormat"
-            }
-        }
+                "class": "NotARealFormat",
+            },
+        },
     })
 
     with pytest.raises(
@@ -329,7 +329,7 @@ def test_config_source_provider_invalid_format():
         match=(
             "failed to create source 'source': "
             "invalid format type 'NotARealFormat'"
-        )
+        ),
     ):
         provider.get_sources()
 
@@ -339,7 +339,7 @@ def test_config_source_provider_invalid_format_kwargs(cls_name):
     provider = ConfigSourceProvider({
         "source": {
             "storage": {
-                "class": "S3File"
+                "class": "S3File",
             },
             "format": {
                 "class": cls_name,
@@ -354,6 +354,6 @@ def test_config_source_provider_invalid_format_kwargs(cls_name):
             "failed to create source 'source': "
             rf"({cls_name}\.)?__init__\(\) got an unexpected keyword argument "
             "'invalid_arg'"
-        )
+        ),
     ):
         provider.get_sources()
diff --git a/tests/test_storage.py b/tests/test_storage.py
index ff6b0e6..7e5baa9 100644
--- a/tests/test_storage.py
+++ b/tests/test_storage.py
@@ -42,8 +42,8 @@ def test_local_file(data_path):
     context = Context(
         files=[{
             "name": "local_file",
-            "path": str(data_path / "local_file.txt")
-        }]
+            "path": str(data_path / "local_file.txt"),
+        }],
     )
     storage = LocalFile(filters={"name": "local_file"})
 
@@ -55,8 +55,8 @@ def test_local_file_name_match(data_path):
     context = Context(
         files=[{
             "name": "local_file",
-            "path": str(data_path / "local_file.txt")
-        }]
+            "path": str(data_path / "local_file.txt"),
+        }],
     )
     storage = LocalFile(filters={"name": "local_.*"})
 
@@ -68,8 +68,8 @@ def test_local_file_int_filter(data_path):
     context = Context(
         files=[{
             "type": 0,
-            "path": str(data_path / "local_file.txt")
-        }]
+            "path": str(data_path / "local_file.txt"),
+        }],
     )
     storage = LocalFile(filters={"type": 0})
 
@@ -84,7 +84,7 @@ def test_local_file_creation():
 
 def test_local_file_name_match_error():
     context = Context(
-        files=[{"name": "local_file"}]
+        files=[{"name": "local_file"}],
     )
     storage = LocalFile(filters={"name": "foo.*"})
 
@@ -110,8 +110,8 @@ def test_s3_file_s3uri(s3_resource):
         files=[{
             "name": "s3_file",
             "bucket": "test-bucket",
-            "key": "bucket_file.txt"
-        }]
+            "key": "bucket_file.txt",
+        }],
     )
     storage = S3File(filters={"name": "s3_file"})
 
@@ -129,8 +129,8 @@ def test_s3_file_s3fs_kwargs(s3_resource):
         files=[{
             "name": "s3_file",
             "bucket": "test-bucket",
-            "key": "bucket_file.txt"
-        }]
+            "key": "bucket_file.txt",
+        }],
     )
     storage = S3File(
         filters={"name": "s3_file"},
@@ -161,24 +161,24 @@ def create_file(bucket, name, contents=None, type="data"):
             "type": type,
             "uri": f"https://example.asf.alaska.edu/{name}",
             "bucket": bucket.name,
-            "key": name
+            "key": name,
         }
 
     context = Context(
         files=[
             create_file(bucket, "file1.txt"),
             create_file(bucket, "file2.txt", type="metadata"),
-        ]
+        ],
     )
 
     storage = S3File(filters={
-        "name": "file1.txt"
+        "name": "file1.txt",
     })
     with storage.open_file(context) as f:
         assert f.read() == b"Content from file1.txt\n"
 
     storage = S3File(filters={
-        "type": "metadata"
+        "type": "metadata",
     })
     with storage.open_file(context) as f:
         assert f.read() == b"Content from file2.txt\n"