diff --git a/pyproject.toml b/pyproject.toml
index 06cdab66..0ee7cb7f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -30,6 +30,7 @@ dependencies = [
   "nbformat>=5.10.4,<6.0",
   "pip-requirements-parser>=32.0.1,<33.1",
   "tomli>=2.1.0,<3.0.0 ; python_version < '3.11'",
+  "typing-extensions>=4.12.2",
 ]
 
 [tool.hatch.version]
@@ -107,6 +108,3 @@ strict = true
 [[tool.mypy.overrides]]
 module = ["dotty_dict.*", "pip_requirements_parser.*", "tomli.*"]
 ignore_missing_imports = true
-
-[tool.pytest.ini_options]
-addopts = "--ignore=tests/manual"
diff --git a/src/creosote/cli.py b/src/creosote/cli.py
index 2d7a473e..81deff6a 100644
--- a/src/creosote/cli.py
+++ b/src/creosote/cli.py
@@ -1,4 +1,6 @@
 import sys
+from collections.abc import Sequence
+from typing import Optional
 
 from loguru import logger
 
@@ -7,17 +9,14 @@
 from creosote.config import Features, fail_fast, parse_args
 
 
-def main(args_=None):
-    args, default_config = parse_args(args_)
+def main(args_: Optional[Sequence[str]] = None) -> int:
+    args = parse_args(args_)
     if fail_fast(args):
         return 1
     formatters.configure_logger(verbose=args.verbose, format_=args.format)
 
     logger.debug(f"Creosote version: {__version__}")
     logger.debug(f"Command: creosote {' '.join(sys.argv[1:])}")
-    logger.debug(
-        f"Default configuration (may have loaded pyproject.toml): {default_config}"
-    )
     logger.debug(f"Arguments: {args}")
 
     if args.features:
diff --git a/src/creosote/config.py b/src/creosote/config.py
index 7979bf4f..78b5aff9 100644
--- a/src/creosote/config.py
+++ b/src/creosote/config.py
@@ -2,13 +2,14 @@
 import os
 import sys
 import typing
+from collections.abc import Sequence
 from dataclasses import dataclass, field
 from enum import Enum
 from pathlib import Path
-from typing import List, Literal
+from typing import Literal, Optional, Union
 
 if sys.version_info >= (3, 11):
-    import tomllib
+    import tomllib  # pyright: ignore[reportUnreachable]
 else:
     import tomli as tomllib
 
@@ -25,15 +26,16 @@ class Config:
     the ``dest`` specified in ``add_argument``.
     """
 
+    verbose: bool = False
     format: Literal["default", "no-color", "porcelain"] = "default"
-    paths: List[str] = field(default_factory=lambda: ["src"])
-    sections: List[str] = field(default_factory=lambda: ["project.dependencies"])
-    exclude_deps: List[str] = field(default_factory=list)
+    paths: list[str] = field(default_factory=lambda: ["src"])
+    sections: list[str] = field(default_factory=lambda: ["project.dependencies"])
+    exclude_deps: list[str] = field(default_factory=list)
     deps_file: str = "pyproject.toml"
-    venvs: List[str] = field(
+    venvs: list[str] = field(
         default_factory=lambda: [os.environ.get("VIRTUAL_ENV", ".venv")]
     )
-    features: List[str] = field(default_factory=list)
+    features: list[str] = field(default_factory=list)
 
 
 class Features(Enum):
@@ -53,24 +55,30 @@ class CustomAppendAction(argparse.Action):
     value when the argument is specified for the first time.
     """
 
-    def __init__(self, option_strings, dest, nargs=None, **kwargs):
+    def __init__(  # type: ignore[no-untyped-def]
+        self,
+        option_strings: list[str],
+        dest: str,
+        nargs: Optional[list[str]] = None,
+        **kwargs,  # pyright: ignore[reportUnknownParameterType, reportMissingParameterType]
+    ):
         """Initialize the action."""
-        self.called_times = 0
-        super().__init__(option_strings, dest, **kwargs)
+        self.called_times: int = 0
+        super().__init__(option_strings, dest, **kwargs)  # pyright: ignore[reportUnknownArgumentType]
 
-    def __call__(self, parser, namespace, values, option_string=None):
+    def __call__(self, parser, namespace, values, option_string=None):  # type: ignore[no-untyped-def]  # pyright: ignore[reportMissingParameterType, reportImplicitOverride]
         """When the argument is specified on the commandline."""
-        current_values = getattr(namespace, self.dest)
+        current_values = getattr(namespace, self.dest)  # pyright: ignore[reportAny]
 
         if self.called_times == 0:
             current_values = []
 
-        current_values.append(values)
+        _ = current_values.append(values)  # pyright: ignore[reportUnknownMemberType]
         setattr(namespace, self.dest, current_values)
         self.called_times += 1
 
 
-def show_migration_message():
+def show_migration_message() -> None:
     """Show warning if you are using v2.x args with v3.x code."""
 
     args = sys.argv[1:]
@@ -79,13 +87,13 @@ def show_migration_message():
         if outdated_arg in args:
             logger.error(
                 "Creosote was updated to v3.x with breaking changes. "
-                "You need to update your CLI arguments. "
-                "See the migration guide at https://github.com/fredrikaverpil/creosote"
+                + "You need to update your CLI arguments. "
+                + "See the migration guide at https://github.com/fredrikaverpil/creosote"
             )
             sys.exit(1)
 
 
-def parse_args(args):
+def parse_args(args: Optional[Sequence[str]]) -> Config:
     show_migration_message()
 
     defaults = load_defaults()
@@ -97,13 +105,14 @@ def parse_args(args):
         ),
         formatter_class=argparse.ArgumentDefaultsHelpFormatter,
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "--verbose",
         dest="verbose",
         action="store_true",
+        default=defaults.verbose,
         help="increase output verbosity",
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "-f",
         "--format",
         dest="format",
@@ -111,7 +120,7 @@ def parse_args(args):
         default=defaults.format,
         help="output format",
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "-V",
         "--version",
         dest="version",
@@ -119,7 +128,7 @@ def parse_args(args):
         version=__version__,
         help="show version and exit",
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "-p",
         "--path",
         dest="paths",
@@ -128,7 +137,7 @@ def parse_args(args):
         default=defaults.paths,
         help="path(s) to Python source code to scan for imports",
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "-s",
         "--section",
         dest="sections",
@@ -137,7 +146,7 @@ def parse_args(args):
         default=defaults.sections,
         help="pyproject.toml section(s) to scan for dependencies",
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "--exclude-dep",
         dest="exclude_deps",
         metavar="DEPENDENCY",
@@ -145,7 +154,7 @@ def parse_args(args):
         default=defaults.exclude_deps,
         help="dependency(ies) to exclude from the scan",
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "-d",
         "--deps-file",
         dest="deps_file",
@@ -153,7 +162,7 @@ def parse_args(args):
         default=defaults.deps_file,
         help="path to the pyproject.toml or requirements[.txt|.in] file",
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "-v",
         "--venv",
         dest="venvs",
@@ -162,7 +171,7 @@ def parse_args(args):
         default=defaults.venvs,
         help="path(s) to the virtual environment (or site-packages)",
     )
-    parser.add_argument(
+    _ = parser.add_argument(
         "--use-feature",
         dest="features",
         metavar="FEATURE",
@@ -176,10 +185,10 @@ def parse_args(args):
     )
 
     parsed_args = parser.parse_args(args)
-    return parsed_args, defaults
+    return Config(**vars(parsed_args))  # pyright: ignore[reportAny]
 
 
-def load_defaults(src: str = "pyproject.toml") -> Config:
+def load_defaults(src: Union[str, Path] = "pyproject.toml") -> Config:
     """Load pyproject.toml defaults from user config.
 
     Expects user configuration at ``[tool.creosote]``.
@@ -190,13 +199,13 @@ def load_defaults(src: str = "pyproject.toml") -> Config:
             project_config = tomllib.load(f)
     except FileNotFoundError:
         project_config = {}
-    creosote_config = project_config.get("tool", {}).get("creosote", {})
+    creosote_config = project_config.get("tool", {}).get("creosote", {})  # pyright: ignore[reportAny]
     # Convert all hyphens to underscores
-    creosote_config = {k.replace("-", "_"): v for k, v in creosote_config.items()}
-    return Config(**creosote_config)
+    creosote_config = {k.replace("-", "_"): v for k, v in creosote_config.items()}  # pyright: ignore[reportAny]
+    return Config(**creosote_config)  # pyright: ignore[reportAny]
 
 
-def fail_fast(args: argparse.Namespace) -> bool:
+def fail_fast(args: Config) -> bool:
     """Check if we should fail fast."""
     if is_missing_file(args.deps_file):
         logger.error(f"File not found: {args.deps_file}")
diff --git a/src/creosote/formatters.py b/src/creosote/formatters.py
index ade899d2..7e65f368 100644
--- a/src/creosote/formatters.py
+++ b/src/creosote/formatters.py
@@ -1,5 +1,4 @@
 import sys
-from typing import List
 
 from loguru import logger
 
@@ -8,10 +7,10 @@ def configure_logger(verbose: bool, format_: str) -> None:
     logger.remove()
 
     if format_ == "porcelain":
-        logger.add(sys.stderr, level="CRITICAL")
+        _ = logger.add(sys.stderr, level="CRITICAL")
         return
     if format_ == "no-color":
-        logger.add(
+        _ = logger.add(
             sys.stderr,
             level="DEBUG" if verbose else "INFO",
             colorize=False,
@@ -19,7 +18,7 @@ def configure_logger(verbose: bool, format_: str) -> None:
         )
     else:
         # default
-        logger.add(
+        _ = logger.add(
             sys.stderr,
             level="DEBUG" if verbose else "INFO",
             colorize=True,
@@ -27,14 +26,14 @@ def configure_logger(verbose: bool, format_: str) -> None:
         )
 
 
-def print_results(unused_dependency_names: List[str], format_: str) -> None:
+def print_results(unused_dependency_names: list[str], format_: str) -> None:
     if unused_dependency_names:
         if format_ == "porcelain":
             print("\n".join(unused_dependency_names))
         else:
             logger.error(
                 "Oh no, bloated venv! 🤢 🪣\n"
-                f"Unused dependencies found: {', '.join(unused_dependency_names)}"
+                + f"Unused dependencies found: {', '.join(unused_dependency_names)}"
             )
     else:
         logger.info("No unused dependencies found! ✨")
diff --git a/src/creosote/models.py b/src/creosote/models.py
index a197bf88..a0d0f519 100644
--- a/src/creosote/models.py
+++ b/src/creosote/models.py
@@ -1,18 +1,18 @@
 import dataclasses
-from typing import List, Optional
+from typing import Optional
 
 
 @dataclasses.dataclass
 class ImportInfo:
-    module: List[str]
-    name: List[str]
+    module: list[str]
+    name: list[str]
     alias: Optional[str] = None
 
 
 @dataclasses.dataclass
 class DependencyInfo:
     name: str  # as defined in the dependencies specification file
-    top_level_import_names: Optional[List[str]] = None
-    record_import_names: Optional[List[str]] = None
+    top_level_import_names: Optional[list[str]] = None
+    record_import_names: Optional[list[str]] = None
     canonicalized_dep_name: Optional[str] = None
-    associated_imports: List[ImportInfo] = dataclasses.field(default_factory=list)
+    associated_imports: list[ImportInfo] = dataclasses.field(default_factory=list)
diff --git a/src/creosote/parsers.py b/src/creosote/parsers.py
index 3c39ecd7..723e9030 100644
--- a/src/creosote/parsers.py
+++ b/src/creosote/parsers.py
@@ -2,23 +2,71 @@
 import re
 import sys
 import tempfile
+from collections.abc import Generator
 from pathlib import Path
-from typing import Any, Dict, Generator, List, Union, cast
+from typing import Union, cast
 
 import nbformat
+from typing_extensions import TypeGuard
 
 if sys.version_info >= (3, 11):
-    import tomllib
+    import tomllib  # pyright: ignore[reportUnreachable]
 else:
     import tomli as tomllib
 
-from dotty_dict import Dotty, dotty
+import dotty_dict  # pyright: ignore[reportMissingTypeStubs]
 from loguru import logger
 from nbconvert import PythonExporter
-from pip_requirements_parser import RequirementsFile
+from pip_requirements_parser import (  # pyright: ignore[reportMissingTypeStubs]
+    RequirementsFile,
+)
 
 from creosote.models import ImportInfo
 
+GroupName = str
+PackageName = str
+PEP621Type1 = list[PackageName]
+PEP621Type2 = dict[GroupName, list[PackageName]]
+PEP621Types = Union[PEP621Type1, PEP621Type2]
+PEP735Type1 = dict[GroupName, list[PackageName]]
+PEP735Type2 = dict[GroupName, list[Union[dict[str, PackageName], str]]]
+PEP735Types = Union[PEP735Type1, PEP735Type2]
+PoetryType1 = dict[PackageName, str]
+PoetryType2 = dict[PackageName, dict[str, str]]
+PoetryTypes = Union[PoetryType1, PoetryType2]
+PipfileType = dict[PackageName, str]
+AllSupportedTypes = Union[
+    PEP621Type1,
+    PEP621Type2,
+    PEP735Type1,
+    PEP735Type2,
+    PoetryType1,
+    PoetryType2,
+    PipfileType,
+]
+
+
+def is_list_type(value: AllSupportedTypes) -> TypeGuard[PEP621Type1]:
+    return isinstance(value, list)
+
+
+def is_dict_of_strings(
+    value: AllSupportedTypes,
+) -> TypeGuard[Union[PoetryType1, PipfileType]]:
+    return isinstance(value, dict) and all(isinstance(v, str) for v in value.values())
+
+
+def is_dict_of_lists(
+    value: AllSupportedTypes,
+) -> TypeGuard[Union[PEP621Type2, PEP735Type1]]:
+    return isinstance(value, dict) and all(isinstance(v, list) for v in value.values())
+
+
+def is_dict_of_dicts(
+    value: AllSupportedTypes,
+) -> TypeGuard[PoetryType2]:
+    return isinstance(value, dict) and all(isinstance(v, dict) for v in value.values())
+
 
 class DependencyReader:
     """Read dependencies from various dependency file formats."""
@@ -26,24 +74,24 @@ class DependencyReader:
     def __init__(
         self,
         deps_file: str,
-        sections: List[str],
-        exclude_deps: List[str],
+        sections: list[str],
+        exclude_deps: list[str],
     ) -> None:
         always_excluded_deps = ["python"]  # occurs in Poetry setup
 
-        self.deps_file = deps_file
-        self.sections = sections
-        self.exclude_deps = exclude_deps + always_excluded_deps
+        self.deps_file: str = deps_file
+        self.sections: list[str] = sections
+        self.exclude_deps: list[str] = exclude_deps + always_excluded_deps
 
-    def read(self) -> List[str]:
+    def read(self) -> list[str]:
         logger.debug(f"Parsing {self.deps_file} for dependencies...")
 
         if not Path(self.deps_file).exists():
             raise Exception(f"File {self.deps_file} does not exist")
 
-        dep_names = []
-        always_excluded_deps = ["python"]  # occurs in Poetry setup
-        deps_to_exclude = always_excluded_deps + self.exclude_deps
+        dep_names: list[str] = []
+        always_excluded_deps: list[str] = ["python"]  # occurs in Poetry setup
+        deps_to_exclude: list[str] = always_excluded_deps + self.exclude_deps
 
         if self.deps_file.endswith(".toml") or self.deps_file.endswith(
             "Pipfile"
@@ -60,32 +108,31 @@ def read(self) -> List[str]:
                 f"Dependency specs file {self.deps_file} is not supported."
             )
 
-        logger.info(
-            f"Found dependencies in {self.deps_file}: " f"{', '.join(dep_names)}"
-        )
+        found = ", ".join(dep_names)
+        logger.info(f"Found dependencies in {self.deps_file}: {found}")
 
         return dep_names
 
     def get_deps_from_pep621_toml(
-        self, section_contents: Union[List[str], Dict[str, List[str]]]
-    ) -> List[str]:
+        self, section_contents: PEP621Types
+    ) -> list[PackageName]:
         """Get dependency names from toml file using the PEP621 spec.
 
         The dependency strings are expected to follow PEP508.
         """
 
-        dep_strings = []
-        if isinstance(section_contents, list):
+        dep_strings: list[str] = []
+        if is_list_type(section_contents):
             for dep_string in section_contents:
                 dep_strings.append(dep_string)
-        elif isinstance(section_contents, dict):
+        elif is_dict_of_lists(section_contents):
             for _, dep_string_list in section_contents.items():
                 for dep_string in dep_string_list:
                     dep_strings.append(dep_string)
         else:
             raise TypeError("Unexpected dependency format, list expected.")
 
-        section_deps = []
+        section_deps: list[PackageName] = []
         for dep_string in dep_strings:
             parsed_dep = self.parse_dep_string(dep_string)
             if parsed_dep:
@@ -96,25 +143,25 @@ def get_deps_from_pep621_toml(
         return section_deps
 
     def get_deps_from_pep735_toml(
-        self, section_contents: Union[List[str], Dict[str, List[str]]]
-    ) -> List[str]:
+        self, section_contents: PEP735Types
+    ) -> list[PackageName]:
         """Get dependency names from toml file using the PEP735 spec.
 
         The dependency strings are expected to follow PEP508.
         """
 
-        dep_strings = []
-        if isinstance(section_contents, dict):
+        dep_strings: list[str] = []
+        if is_dict_of_lists(section_contents):
             for _, dep_string_list in section_contents.items():
                 for dep_string in dep_string_list:
-                    if type(dep_string) != str:
+                    if type(dep_string) is not str:
                         logger.debug(f"Skipping non-string entry: {dep_string}")
                         continue
                     dep_strings.append(dep_string)
         else:
             raise TypeError("Unexpected dependency format, list expected.")
 
-        section_deps = []
+        section_deps: list[PackageName] = []
         for dep_string in dep_strings:
             parsed_dep = self.parse_dep_string(dep_string)
             if parsed_dep:
@@ -126,48 +173,55 @@ def get_deps_from_pep735_toml(
 
     def get_deps_from_toml_section_keys(
         self,
-        section_contents: Dict[str, Any],
-    ):
+        section_contents: Union[PoetryTypes, PipfileType],
+    ) -> list[PackageName]:
         """Get dependency names from toml section's dict keys."""
-        if not isinstance(section_contents, dict):
-            raise TypeError("Unexpected dependency format, dict expected.")
-        return section_contents.keys()
+        if is_dict_of_strings(section_contents) or is_dict_of_dicts(section_contents):
+            return list(section_contents.keys())
+
+        raise TypeError("Unexpected dependency format, dict expected.")
 
-    def read_toml(self, deps_file: str, sections: List[str]) -> List[str]:
+    def read_toml(self, deps_file: str, sections: list[str]) -> list[str]:
         """Read dependency names from toml spec file."""
         with open(deps_file, "rb") as infile:
             contents = tomllib.load(infile)
 
-        dotty_contents: Dotty = dotty(contents)
-        dep_names = []
+        dotty_contents = dotty_dict.dotty(contents)  # pyright: ignore[reportUnknownMemberType]
+        dep_names: list[str] = []
 
         for section in sections:
             try:
-                section_contents = dotty_contents[section]
+                section_contents = cast(AllSupportedTypes, dotty_contents[section])
             except KeyError as err:
                 raise KeyError(f"Could not find toml section {section}.") from err
 
             logger.debug(f"{sections}: {section_contents}")
 
-            section_dep_names = []
+            section_dep_names: list[str] = []
             if section.startswith("project."):
                 logger.debug(f"Detected PEP-621 toml section in {deps_file}")
-                section_dep_names = self.get_deps_from_pep621_toml(section_contents)
+                section_dep_names = self.get_deps_from_pep621_toml(
+                    cast(PEP621Types, section_contents)
+                )
             elif section.startswith("tool.pdm"):
                 logger.debug(f"Detected PDM toml section in {deps_file}")
-                section_dep_names = self.get_deps_from_pep621_toml(section_contents)
+                section_dep_names = self.get_deps_from_pep621_toml(
+                    cast(PEP621Types, section_contents)
+                )
             elif section.startswith("dependency-groups"):
                 logger.debug(f"Detected PEP-735 toml section in {deps_file}")
-                section_dep_names = self.get_deps_from_pep735_toml(section_contents)
+                section_dep_names = self.get_deps_from_pep735_toml(
+                    cast(PEP735Types, section_contents)
+                )
             elif section.startswith("tool.poetry"):
                 logger.debug(f"Detected Poetry toml section in {deps_file}")
                 section_dep_names = self.get_deps_from_toml_section_keys(
-                    cast(dict, section_contents)
+                    cast(PoetryTypes, section_contents)
                 )
             elif section.startswith("packages") or section.startswith("dev-packages"):
                 logger.debug(f"Detected pipenv/Pipfile toml section in {deps_file}")
                 section_dep_names = self.get_deps_from_toml_section_keys(
-                    cast(dict, section_contents)
+                    cast(PipfileType, section_contents)
                 )
             else:
                 raise TypeError("Unsupported dependency format.")
@@ -179,7 +233,7 @@ def read_toml(self, deps_file: str, sections: List[str]) -> List[str]:
 
         return sorted(dep_names)
 
-    def read_requirements(self, deps_file: str) -> List[str]:
+    def read_requirements(self, deps_file: str) -> list[str]:
         """Read dependency names from requirements.txt-format file."""
         dep_from_req = RequirementsFile.from_file(deps_file).requirements
         return sorted([dep.name for dep in dep_from_req if dep.name is not None])
@@ -229,14 +283,18 @@ def get_module_info_from_python_file(path: str) -> Generator[ImportInfo, None, N
     is_notebook = False
     if Path(path).suffix == ".ipynb":
         with open(path) as f:
-            notebook_content = nbformat.read(f, as_version=4)
-
+            notebook_content = nbformat.read(  # type: ignore[no-untyped-call]  # pyright: ignore[reportUnknownMemberType, reportUnknownVariableType]
+                f,
+                as_version=4,
+            )
         # Convert the notebook to a temporary .py file
-        body, _ = PythonExporter().from_notebook_node(notebook_content)
+        body, _ = PythonExporter().from_notebook_node(  # type: ignore[no-untyped-call]
+            notebook_content  # pyright: ignore[reportUnknownArgumentType]
+        )
 
         # delete_on_close parameter only supported in Python 3.12+
         with tempfile.NamedTemporaryFile(delete=False, suffix=".py") as temp_file:
-            temp_file.write(body.encode("utf-8"))
+            _ = temp_file.write(body.encode("utf-8"))
             path = temp_file.name
             is_notebook = True
 
@@ -267,9 +325,9 @@ def get_module_info_from_python_file(path: str) -> Generator[ImportInfo, None, N
         Path(path).unlink()
 
 
-def get_module_names_from_code(paths: List[str]) -> List[ImportInfo]:
-    resolved_paths: List[Path] = []
-    imports = []
+def get_module_names_from_code(paths: list[str]) -> list[ImportInfo]:
+    resolved_paths: list[Path] = []
+    imports: list[ImportInfo] = []
 
     for path in paths:
         if Path(path).is_dir():
@@ -283,7 +341,7 @@ def get_module_names_from_code(paths: List[str]) -> List[ImportInfo]:
         for import_info in get_module_info_from_python_file(path=str(resolved_path)):
             imports.append(import_info)
 
-    imports_with_dupes_removed = []
+    imports_with_dupes_removed: list[ImportInfo] = []
     for import_info in imports:
         if import_info not in imports_with_dupes_removed:
             imports_with_dupes_removed.append(import_info)
@@ -295,17 +353,17 @@ def get_module_names_from_code(paths: List[str]) -> List[ImportInfo]:
     return imports_with_dupes_removed
 
 
-def get_installed_dependency_names(venv: str) -> List[str]:
-    dep_names = []
+def get_installed_dependency_names(venv: str) -> list[str]:
+    dep_names: list[str] = []
     for path in Path(venv).glob("**/*.dist-info"):
         dep_names.append(path.name.split("-")[0])
     return dep_names
 
 
 def get_excluded_deps_which_are_not_installed(
-    excluded_deps: List[str], venvs: List[str]
-) -> List[str]:
-    dependency_names: List[str] = []
+    excluded_deps: list[str], venvs: list[str]
+) -> list[str]:
+    dependency_names: list[str] = []
     if not excluded_deps:
         return dependency_names
 
@@ -323,7 +381,7 @@ def get_excluded_deps_which_are_not_installed(
     if dependency_names:
         logger.warning(
             "Excluded dependencies not found in virtual environment: "
-            f"{', '.join(dependency_names)}"
+            + f"{', '.join(dependency_names)}"
         )
     return dependency_names
 
diff --git a/src/creosote/py.typed b/src/creosote/py.typed
new file mode 100644
index 00000000..e69de29b
diff --git a/src/creosote/resolvers.py b/src/creosote/resolvers.py
index 4715ed15..baab63df 100644
--- a/src/creosote/resolvers.py
+++ b/src/creosote/resolvers.py
@@ -2,7 +2,6 @@
 import pathlib
 import re
 from pathlib import Path
-from typing import List
 
 from loguru import logger
 
@@ -12,24 +11,26 @@
 class DepsResolver:
     def __init__(
         self,
-        imports: List[ImportInfo],
-        dependency_names: List[str],
-        venvs: List[str],
+        imports: list[ImportInfo],
+        dependency_names: list[str],
+        venvs: list[str],
     ):
-        self.imports: List[ImportInfo] = imports
-        self.dependencies: List[DependencyInfo] = [
+        self.imports: list[ImportInfo] = imports
+        self.dependencies: list[DependencyInfo] = [
             DependencyInfo(name=dep) for dep in dependency_names
         ]
-        self.venvs: List[str] = venvs
+        self.venvs: list[str] = venvs
 
-        self.top_level_txt_pattern = re.compile(
+        self.top_level_txt_pattern: re.Pattern[str] = re.compile(
             r"\/([\w\.]*).[\d\.]*.dist-info\/top_level.txt"
         )
-        self.record_pattern = re.compile(r"\/([\w\.]*).[\d\.]*.dist-info\/RECORD")
+        self.record_pattern: re.Pattern[str] = re.compile(
+            r"\/([\w\.]*).[\d\.]*.dist-info\/RECORD"
+        )
 
-        self.top_level_filepaths: List[pathlib.Path] = []
-        self.record_filepaths: List[pathlib.Path] = []
-        self.unused_deps: List[DependencyInfo] = []
+        self.top_level_filepaths: list[pathlib.Path] = []
+        self.record_filepaths: list[pathlib.Path] = []
+        self.unused_deps: list[DependencyInfo] = []
 
     @staticmethod
     def canonicalize_module_name(module_name: str) -> str:
@@ -42,7 +43,7 @@ def is_importable(self, module_name: str) -> bool:
         except ImportError:
             return False
 
-    def gather_filepaths(self, venv: str, glob_str: str) -> List[Path]:
+    def gather_filepaths(self, venv: str, glob_str: str) -> list[Path]:
         logger.debug(f"Gathering all top_level.txt files in venv {venv}...")
         venv_path = pathlib.Path(venv)
         filepaths = list(venv_path.glob(glob_str))
@@ -82,7 +83,9 @@ def map_dep_to_import_via_top_level_txt_file(
 
         for top_level_filepath in self.top_level_filepaths:
             normalized_top_level_filepath = top_level_filepath.as_posix()
-            matches = self.top_level_txt_pattern.findall(normalized_top_level_filepath)
+            matches: list[str] = self.top_level_txt_pattern.findall(
+                normalized_top_level_filepath
+            )
             for name_from_top_level in matches:
                 if (
                     self.canonicalize_module_name(name_from_top_level).lower()
@@ -96,7 +99,7 @@ def map_dep_to_import_via_top_level_txt_file(
                     import_names = ", ".join(dep_info.top_level_import_names)
                     logger.debug(
                         f"[{dep_info.name}] found import name(s) "
-                        f"via top_level.txt: {import_names} ⭐️"
+                        + f"via top_level.txt: {import_names} ⭐️"
                     )
                     return True
         logger.debug(f"[{dep_info.name}] did not find dep in a top_level.txt file")
@@ -105,7 +108,7 @@ def map_dep_to_import_via_top_level_txt_file(
     def map_dep_to_import_via_record_file(self, dep_info: DependencyInfo) -> bool:
         for record_filepath in self.record_filepaths:
             normalized_record_filepath = record_filepath.as_posix()
-            matches = self.record_pattern.findall(normalized_record_filepath)
+            matches: list[str] = self.record_pattern.findall(normalized_record_filepath)
             for name_from_record in matches:
                 if (
                     self.canonicalize_module_name(name_from_record).lower()
@@ -116,7 +119,7 @@ def map_dep_to_import_via_record_file(self, dep_info: DependencyInfo) -> bool:
                     ) as infile:
                         lines = infile.readlines()
 
-                    import_names_found = []
+                    import_names_found: list[str] = []
                     for line in lines:
                         candidate, _hash, _size = line.split(",")
                         if candidate.endswith(".py") and "__init__" in candidate:
@@ -129,7 +132,7 @@ def map_dep_to_import_via_record_file(self, dep_info: DependencyInfo) -> bool:
                             import_names = ",".join(dep_info.record_import_names)
                             logger.debug(
                                 f"[{dep_info.name}] found import name "
-                                f"via RECORD: {import_names} ⭐️"
+                                + f"via RECORD: {import_names} ⭐️"
                             )
                             return True
 
@@ -139,7 +142,7 @@ def map_dep_to_import_via_record_file(self, dep_info: DependencyInfo) -> bool:
     def map_dep_to_canonical_name(self, dep_info: DependencyInfo) -> str:
         return self.canonicalize_module_name(dep_info.name)
 
-    def populate_dependency_info(self):
+    def populate_dependency_info(self) -> None:
         """Populate DependencyInfo object with import naming info.
 
         There are three strategies from where the import name can be
@@ -168,10 +171,12 @@ def populate_dependency_info(self):
             if not found_via_top_level_txt and not found_via_record:
                 logger.debug(
                     f"[{dep_info.name}] relying on canonicalization "
-                    f"fallback: {dep_info.canonicalized_dep_name } 🤞"
+                    + f"fallback: {dep_info.canonicalized_dep_name } 🤞"
                 )
 
-    def associate_dep_with_import(self, dep_info: DependencyInfo, import_name: str):
+    def associate_dep_with_import(
+        self, dep_info: DependencyInfo, import_name: str
+    ) -> None:
         for imp in self.imports.copy():
             if not imp.module and import_name in imp.name:
                 # import <imp.name>
@@ -181,7 +186,7 @@ def associate_dep_with_import(self, dep_info: DependencyInfo, import_name: str):
                 # from <imp.name> import ...
                 dep_info.associated_imports.append(imp)
 
-    def resolve(self):
+    def resolve(self) -> None:
         """Associate dependency name with import (module) name.
 
         The AST has found imports from the source code. This function
@@ -208,13 +213,13 @@ def get_unused_dependencies(self) -> None:
             if not dep_info.associated_imports
         ]
 
-    def resolve_unused_dependency_names(self) -> List[str]:
+    def resolve_unused_dependency_names(self) -> list[str]:
         for venv in self.venvs:
             if not Path(venv).exists():
                 logger.warning(
                     f"Virtual environment(s) '{', '.join(self.venvs)}' does not exist, "
-                    "cannot resolve top-level names. "
-                    "This may lead to incorrect results."
+                    + "cannot resolve top-level names. "
+                    + "This may lead to incorrect results."
                 )
             self.gather_top_level_filepaths(venv=venv)
             self.gather_record_filepaths(venv=venv)
@@ -225,7 +230,7 @@ def resolve_unused_dependency_names(self) -> List[str]:
 
         logger.debug(
             "Dependencies with populated 'associated_import' attribute are used in "
-            "code. End result of resolve:"
+            + "code. End result of resolve:"
         )
         for dep_info in self.dependencies:
             logger.debug(f"- {dep_info}")
diff --git a/tests/test_config_loading.py b/tests/test_config_loading.py
index 120fa73b..a3addcf5 100644
--- a/tests/test_config_loading.py
+++ b/tests/test_config_loading.py
@@ -1,39 +1,40 @@
 import os
+from pathlib import Path
 
 from creosote import config
 
 
-def test_load_defaults_no_file(tmp_path):
+def test_load_defaults_no_file(tmp_path: Path) -> None:
     pyproject = tmp_path / "pyproject.toml"
     configuration = config.load_defaults(pyproject)
     assert configuration == config.Config()  # Should return a default config
 
 
-def test_load_defaults_no_tool_section(tmp_path):
+def test_load_defaults_no_tool_section(tmp_path: Path) -> None:
     pyproject = tmp_path / "pyproject.toml"
-    pyproject.write_text("[foo]")
+    _ = pyproject.write_text("[foo]")
     configuration = config.load_defaults(pyproject)
     assert configuration == config.Config()  # Should return a default config
 
 
-def test_load_defaults_no_tool_creosote_section(tmp_path):
+def test_load_defaults_no_tool_creosote_section(tmp_path: Path) -> None:
     pyproject = tmp_path / "pyproject.toml"
-    pyproject.write_text("[tool.foo]")
+    _ = pyproject.write_text("[tool.foo]")
     configuration = config.load_defaults(pyproject)
     assert configuration == config.Config()  # Should return a default config
 
 
-def test_load_defaults_tool_creosote_section_simple(tmp_path):
+def test_load_defaults_tool_creosote_section_simple(tmp_path: Path) -> None:
     pyproject = tmp_path / "pyproject.toml"
-    pyproject.write_text('[tool.creosote]\nvenvs=["foo"]')
+    _ = pyproject.write_text('[tool.creosote]\nvenvs=["foo"]')
     configuration = config.load_defaults(pyproject)
     assert configuration == config.Config(venvs=["foo"])
 
 
-def test_load_defaults_tool_creosote_section_complex(tmp_path):
+def test_load_defaults_tool_creosote_section_complex(tmp_path: Path) -> None:
     """More close to a real configuration."""
     pyproject = tmp_path / "pyproject.toml"
-    pyproject.write_text(
+    _ = pyproject.write_text(
         """
         [tool.creosote]
         venvs=[".virtual_environment"]
@@ -57,14 +58,14 @@ def test_load_defaults_tool_creosote_section_complex(tmp_path):
     )
 
 
-def test_load_defaults_no_venv():
+def test_load_defaults_no_venv() -> None:
     # Unset VIRTUAL_ENV environment variable
-    os.environ.pop("VIRTUAL_ENV", None)
+    _ = os.environ.pop("VIRTUAL_ENV", None)
     configuration = config.Config()
     assert configuration.venvs == [".venv"]
 
 
-def test_load_defaults_set_venv():
+def test_load_defaults_set_venv() -> None:
     os.environ["VIRTUAL_ENV"] = "foo"
     configuration = config.Config()
     assert configuration.venvs == ["foo"]
diff --git a/tests/test_custom_append_action.py b/tests/test_custom_append_action.py
index cc823d9d..2df6bc12 100644
--- a/tests/test_custom_append_action.py
+++ b/tests/test_custom_append_action.py
@@ -3,42 +3,42 @@
 from creosote.config import CustomAppendAction
 
 
-def test_custom_append_action_none_default():
+def test_custom_append_action_none_default() -> None:
     parser = argparse.ArgumentParser()
-    parser.add_argument("-f", "--foo", dest="foo", action=CustomAppendAction)
+    _ = parser.add_argument("-f", "--foo", dest="foo", action=CustomAppendAction)
     args = parser.parse_args(["-f", "1", "-f", "2"])
-    assert args.foo == ["1", "2"]
+    assert args.foo == ["1", "2"]  # pyright: ignore[reportAny]
 
 
-def test_custom_append_action_list_default():
+def test_custom_append_action_list_default() -> None:
     parser = argparse.ArgumentParser()
-    parser.add_argument(
+    _ = parser.add_argument(
         "-f", "--foo", dest="foo", action=CustomAppendAction, default=["3"]
     )
     args = parser.parse_args([])
-    assert args.foo == ["3"]
+    assert args.foo == ["3"]  # pyright: ignore[reportAny]
 
 
-def test_custom_append_action_list_default_override():
+def test_custom_append_action_list_default_override() -> None:
     parser = argparse.ArgumentParser()
-    parser.add_argument(
+    _ = parser.add_argument(
         "-f", "--foo", dest="foo", action=CustomAppendAction, default=["3"]
     )
     args = parser.parse_args(["-f", "1", "-f", "2"])
-    assert args.foo == ["1", "2"]
+    assert args.foo == ["1", "2"]  # pyright: ignore[reportAny]
 
 
-def test_custom_append_action_list_set_defaults():
+def test_custom_append_action_list_set_defaults() -> None:
     parser = argparse.ArgumentParser()
-    parser.add_argument("-f", "--foo", dest="foo", action=CustomAppendAction)
+    _ = parser.add_argument("-f", "--foo", dest="foo", action=CustomAppendAction)
     parser.set_defaults(foo=["3"])
     args = parser.parse_args([])
-    assert args.foo == ["3"]
+    assert args.foo == ["3"]  # pyright: ignore[reportAny]
 
 
-def test_custom_append_action_list_set_defaults_override():
+def test_custom_append_action_list_set_defaults_override() -> None:
     parser = argparse.ArgumentParser()
-    parser.add_argument("-f", "--foo", dest="foo", action=CustomAppendAction)
+    _ = parser.add_argument("-f", "--foo", dest="foo", action=CustomAppendAction)
     parser.set_defaults(foo=["3"])
     args = parser.parse_args(["-f", "1", "-f", "2"])
-    assert args.foo == ["1", "2"]
+    assert args.foo == ["1", "2"]  # pyright: ignore[reportAny]
diff --git a/tests/test_dependency_reader.py b/tests/test_dependency_reader.py
index 379fb548..70bf8369 100644
--- a/tests/test_dependency_reader.py
+++ b/tests/test_dependency_reader.py
@@ -1,5 +1,3 @@
-from typing import List
-
 import pytest
 
 from creosote.parsers import DependencyReader
@@ -27,7 +25,9 @@
         ),
     ],
 )
-def test_read_toml_pep621(sections: List[str], expected_dependencies: List[str]):
+def test_read_toml_pep621(
+    sections: list[str], expected_dependencies: list[str]
+) -> None:
     reader = DependencyReader(
         deps_file="tests/deps_files/pyproject.pep621.toml",
         sections=sections,
@@ -54,7 +54,9 @@ def test_read_toml_pep621(sections: List[str], expected_dependencies: List[str])
         ),
     ],
 )
-def test_read_toml_pep735(sections: List[str], expected_dependencies: List[str]):
+def test_read_toml_pep735(
+    sections: list[str], expected_dependencies: list[str]
+) -> None:
     reader = DependencyReader(
         deps_file="tests/deps_files/pyproject.pep735.toml",
         sections=sections,
@@ -81,7 +83,9 @@ def test_read_toml_pep735(sections: List[str], expected_dependencies: List[str])
         ),
     ],
 )
-def test_read_toml_poetry(sections: List[str], expected_dependencies: List[str]):
+def test_read_toml_poetry(
+    sections: list[str], expected_dependencies: list[str]
+) -> None:
     reader = DependencyReader(
         deps_file="tests/deps_files/pyproject.poetry.toml",
         sections=sections,
@@ -98,7 +102,9 @@ def test_read_toml_poetry(sections: List[str], expected_dependencies: List[str])
         (["dev-packages"], ["pytest"]),
     ],
 )
-def test_read_toml_pipfile(sections: List[str], expected_dependencies: List[str]):
+def test_read_toml_pipfile(
+    sections: list[str], expected_dependencies: list[str]
+) -> None:
     reader = DependencyReader(
         deps_file="tests/deps_files/Pipfile",
         sections=sections,
@@ -119,7 +125,9 @@ def test_read_toml_pipfile(sections: List[str], expected_dependencies: List[str]
         ("Qt_py==1.0.0", "Qt_py"),
     ],
 )
-def test_dependency_without_version_constraint(dependency_string, expected_package):
+def test_dependency_without_version_constraint(
+    dependency_string: str, expected_package: str
+) -> None:
     assert expected_package == DependencyReader.dependency_without_version_constraint(
         dependency_string
     )
@@ -134,7 +142,9 @@ def test_dependency_without_version_constraint(dependency_string, expected_packa
         ("pip @ git+ssh://git@github.com/pypa/pip.git", "pip"),
     ],
 )
-def test_pyproject_directref_package_name(dependency_string, expected_package):
+def test_pyproject_directref_package_name(
+    dependency_string: str, expected_package: str
+) -> None:
     assert expected_package == DependencyReader.dependency_without_direct_reference(
         dependency_string
     )
diff --git a/tests/test_integration.py b/tests/test_integration.py
index e4707a6e..6b1154f6 100644
--- a/tests/test_integration.py
+++ b/tests/test_integration.py
@@ -1,5 +1,6 @@
 """This file holds all integration tests.
 
+
 The general idea:
 - Invoke the test by runing the CLI and provide arguments.
 - Assert on the output.
@@ -12,7 +13,7 @@
 
 """
 
-from typing import List
+from typing import Any
 
 import pytest
 from _pytest.capture import CaptureFixture
@@ -23,7 +24,7 @@
 
 def test_creosote_project_success(
     venv_manager: VenvManager,
-    capsys: CaptureFixture,
+    capsys: CaptureFixture[Any],  # pyright: ignore[reportExplicitAny]
 ) -> None:
     """Test running cresote on its own project, successfully."""
 
@@ -38,7 +39,7 @@ def test_creosote_project_success(
         "pip-requirements-parser",
         "tomli",
     ]:
-        venv_manager.create_record(
+        _ = venv_manager.create_record(
             site_packages_path=site_packages_path,
             dependency_name=dependency_name,
             contents=[
@@ -68,7 +69,8 @@ def test_creosote_project_success(
 
     assert actual_output == [
         "Found dependencies in pyproject.toml: "
-        "dotty-dict, loguru, nbconvert, nbformat, pip-requirements-parser",
+        + "dotty-dict, loguru, nbconvert, nbformat, pip-requirements-parser, "
+        + "typing-extensions",
         "No unused dependencies found! ✨",
     ]
     assert exit_code == 0
@@ -186,11 +188,11 @@ def test_creosote_project_success(
 @pytest.mark.parametrize(["scan_type"], [["RECORD"], ["top_level.txt"]])
 def test_no_unused_dependencies_found(  # noqa: PLR0913
     venv_manager: VenvManager,
-    capsys: CaptureFixture,
+    capsys: CaptureFixture[Any],  # pyright: ignore[reportExplicitAny]
     scan_type: str,
     deps_filename: str,
     toml_section: str,
-    deps_file_contents: List[str],
+    deps_file_contents: list[str],
 ) -> None:
     """Test simulated setup without any unused dependencies found."""
 
@@ -212,7 +214,7 @@ def test_no_unused_dependencies_found(  # noqa: PLR0913
 
     for dependency_name in installed_dependencies:
         if scan_type == "RECORD":
-            venv_manager.create_record(
+            _ = venv_manager.create_record(
                 site_packages_path=site_packages_path,
                 dependency_name=dependency_name,
                 contents=[
@@ -220,7 +222,7 @@ def test_no_unused_dependencies_found(  # noqa: PLR0913
                 ],
             )
         elif scan_type == "top_level.txt":
-            venv_manager.create_top_level_txt(
+            _ = venv_manager.create_top_level_txt(
                 site_packages_path=site_packages_path,
                 dependency_name=dependency_name,
                 contents=["yolo"],
@@ -265,7 +267,7 @@ def test_no_unused_dependencies_found(  # noqa: PLR0913
 
     assert actual_output == [
         f"Found dependencies in {deps_filepath}: "
-        "dotty-dict, loguru, pip-requirements-parser, toml",
+        + "dotty-dict, loguru, pip-requirements-parser, toml",
         "No unused dependencies found! ✨",
     ]
     assert exit_code == 0
@@ -392,11 +394,11 @@ def test_no_unused_dependencies_found(  # noqa: PLR0913
 @pytest.mark.parametrize(["unused_dep_is_installed"], [[False], [True]])
 def test_one_unused_dependency_found(  # noqa: PLR0913
     venv_manager: VenvManager,
-    capsys: CaptureFixture,
+    capsys: CaptureFixture[Any],  # pyright: ignore[reportExplicitAny]
     scan_type: str,
     deps_filename: str,
     toml_section: str,
-    deps_file_contents: List[str],
+    deps_file_contents: list[str],
     exclude_unused_dep: bool,
     unused_dep_is_installed: bool,
 ) -> None:
@@ -429,7 +431,7 @@ def test_one_unused_dependency_found(  # noqa: PLR0913
 
     for dependency_name in installed_dependencies:
         if scan_type == "RECORD":
-            venv_manager.create_record(
+            _ = venv_manager.create_record(
                 site_packages_path=site_packages_path,
                 dependency_name=dependency_name,
                 contents=[
@@ -437,7 +439,7 @@ def test_one_unused_dependency_found(  # noqa: PLR0913
                 ],
             )
         elif scan_type == "top_level.txt":
-            venv_manager.create_top_level_txt(
+            _ = venv_manager.create_top_level_txt(
                 site_packages_path=site_packages_path,
                 dependency_name=dependency_name,
                 contents=["yolo"],
@@ -502,7 +504,8 @@ def test_one_unused_dependency_found(  # noqa: PLR0913
 
 
 def test_repeated_arguments_are_accepted(
-    venv_manager: VenvManager, capsys: CaptureFixture
+    venv_manager: VenvManager,
+    capsys: CaptureFixture[Any],  # pyright: ignore[reportExplicitAny]
 ) -> None:
     """The same argument is passed multiple times, when supported."""
 
@@ -546,7 +549,7 @@ def test_repeated_arguments_are_accepted(
     imports = deps_and_imports_map.values()
 
     for dependency_name in installed_dependencies:
-        venv_manager.create_record(
+        _ = venv_manager.create_record(
             site_packages_path=site_packages_path,
             dependency_name=dependency_name,
             contents=[
@@ -598,8 +601,9 @@ def test_repeated_arguments_are_accepted(
     assert exit_code == 0
 
 
-def test_repeated_arguments_are_accepted(
-    venv_manager: VenvManager, capsys: CaptureFixture
+def test_ruamel(
+    venv_manager: VenvManager,
+    capsys: CaptureFixture[Any],  # pyright: ignore[reportExplicitAny]
 ) -> None:
     """Asserts that ruamel.yaml is supported."""
 
@@ -627,7 +631,7 @@ def test_repeated_arguments_are_accepted(
     imports = deps_and_imports_map.values()
 
     for dependency_name in installed_dependencies:
-        venv_manager.create_record(
+        _ = venv_manager.create_record(
             site_packages_path=site_packages_path,
             dependency_name=dependency_name,
             contents=[
diff --git a/tests/test_integration_notebook.py b/tests/test_integration_notebook.py
index 58e47ef3..f3ed5b2c 100644
--- a/tests/test_integration_notebook.py
+++ b/tests/test_integration_notebook.py
@@ -1,3 +1,5 @@
+from typing import Any
+
 from _pytest.capture import CaptureFixture
 
 from creosote import cli
@@ -6,8 +8,8 @@
 
 def test_jupyter_ok(
     venv_manager: VenvManager,
-    capsys: CaptureFixture,
-):
+    capsys: CaptureFixture[Any],  # pyright: ignore[reportExplicitAny]
+) -> None:
     venv_path, site_packages_path = venv_manager.create_venv()
 
     deps_filename = "pyproject.toml"
@@ -26,7 +28,7 @@ def test_jupyter_ok(
     ]
 
     for dependency_name in installed_dependencies:
-        venv_manager.create_record(
+        _ = venv_manager.create_record(
             site_packages_path=site_packages_path,
             dependency_name=dependency_name,
             contents=[