diff --git a/main.py b/main.py
deleted file mode 100644
index db48b90..0000000
--- a/main.py
+++ /dev/null
@@ -1,6 +0,0 @@
-def main():
-    print("Hello from python-utils!")
-
-
-if __name__ == "__main__":
-    main()
diff --git a/pyproject.toml b/pyproject.toml
index 55945c1..aec63d4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,3 +24,20 @@ dev = [
     "ruff>=0.12.10",
     "safety>=3.6.0",
 ]
+
+[tool.mypy]
+python_version = "3.10"
+warn_return_any = true  # nudge to use stricter types
+warn_unused_configs = true  # nudge to remove unused configs
+disallow_untyped_defs = true  # disallow untyped function definitions
+disallow_incomplete_defs = true  # ensure all parts of a function has type annotation
+check_untyped_defs = true  # dont skip untyped functions
+disallow_untyped_decorators = false  # allow untyped decorators to keep code more readable
+no_implicit_optional = true  # disallow implicit optional types leading to None-mess
+warn_redundant_casts = true  # nudge to use explicit type casts
+warn_unused_ignores = true  # nudge to remove unused ignores
+warn_no_return = true  # catch missing return statements
+warn_unreachable = true  # catch unreachable code
+show_error_codes = true  # show error codes in output
+explicit_package_bases = true  # reduce risk of import confusion
+namespace_packages = true  # enable namespace packages
diff --git a/python_utils/__init__.py b/python_utils/__init__.py
index e69de29..60e6d80 100644
--- a/python_utils/__init__.py
+++ b/python_utils/__init__.py
@@ -0,0 +1,4 @@
+from .check_env import check_env as check_env
+from .readable_unit import readable_unit as readable_unit
+
+__all__ = ["check_env", "readable_unit"]
diff --git a/python_utils/check_env.py b/python_utils/check_env.py
index 63f61af..1b4a91e 100644
--- a/python_utils/check_env.py
+++ b/python_utils/check_env.py
@@ -5,7 +5,7 @@ import os
 
 
 def check_env(
-    var_list: str | list[str],
+    var_list: str | set[str] | list[str] | tuple[str, ...],
     missing_ok: bool = False,
 ) -> None:
     """Check if environment variables are set.
diff --git a/tests/unit/check_env_test.py b/tests/unit/check_env_test.py
index e5cf166..bda970e 100644
--- a/tests/unit/check_env_test.py
+++ b/tests/unit/check_env_test.py
@@ -3,12 +3,15 @@
 import os
 import unittest
 
-from pytohn_utils import check_env
+from python_utils import check_env
 
 
 class TestCheckEnv(unittest.TestCase):
+    set_vars: list[str]
+    unset_var: str
+
     @classmethod
-    def setUpClass(cls):
+    def setUpClass(cls) -> None:
         """Set up test environment variables."""
         cls.set_vars = ["A", "B", "C"]
         for var in cls.set_vars:
@@ -20,41 +23,41 @@ class TestCheckEnv(unittest.TestCase):
             )
 
     @classmethod
-    def tearDownClass(cls):
+    def tearDownClass(cls) -> None:
         for var in cls.set_vars:
             if var in os.environ:
                 del os.environ[var]
             os.environ.pop(var, None)
 
-    def test_check_env_accepts_single_string(self):
+    def test_check_env_accepts_single_string(self) -> None:
         """Test check_env function with a valid single string."""
-        self.assertIsNone(check_env(self.set_vars[0]))
+        check_env(self.set_vars[0])
 
-    def test_check_env_accepts_list_of_strings(self):
+    def test_check_env_accepts_list_of_strings(self) -> None:
         """Test check_env function with a valid list of strings."""
-        self.assertIsNone(check_env(self.set_vars))
+        check_env(self.set_vars)
 
-    def test_check_env_accepts_set_of_strings(self):
+    def test_check_env_accepts_set_of_strings(self) -> None:
         """Test check_env function with a valid set of strings."""
-        self.assertIsNone(check_env(set(self.set_vars)))
+        check_env(set(self.set_vars))
 
-    def test_check_env_accepts_tuple_of_strings(self):
+    def test_check_env_accepts_tuple_of_strings(self) -> None:
         """Test check_env function with a valid tuple of strings."""
-        self.assertIsNone(check_env(tuple(self.set_vars)))
+        check_env(tuple(self.set_vars))
 
-    def test_check_env_rejects_empty_list(self):
+    def test_check_env_rejects_empty_list(self) -> None:
         """Test check_env function with an empty list."""
         with self.assertRaises(ValueError):
             check_env([])
 
-    def test_check_env_raises_error_on_missing_vars(self):
+    def test_check_env_raises_error_on_missing_vars(self) -> None:
         """Test check_env function with missing environment variables."""
         with self.assertRaises(OSError):
             check_env(self.unset_var)
 
-    def test_check_env_does_not_raise_error_when_missing_ok_flag_set(self):
+    def test_check_env_does_not_raise_error_when_missing_ok_flag_set(self) -> None:
         """Test that check_env does not raise an error when the environment variable is missing and missing_ok=True.
 
         The 'missing_ok' flag allows the function to skip raising an error if the specified environment variable(s) are not set.
         """
-        self.assertIsNone(check_env(self.unset_var, missing_ok=True))
+        check_env(self.unset_var, missing_ok=True)
diff --git a/tests/unit/readable_unit_test.py b/tests/unit/readable_unit_test.py
index 98e631f..23b1e11 100644
--- a/tests/unit/readable_unit_test.py
+++ b/tests/unit/readable_unit_test.py
@@ -1,6 +1,7 @@
 """Unittests for the readable function."""
 
 import pytest
+from typing import Any
 
 from python_utils import readable_unit
 
@@ -31,7 +32,11 @@ TEST_CASES = [
 
 
 @pytest.mark.parametrize("value, unit, expected", TEST_CASES)
-def test_readable_unit(value, unit, expected):
+def test_readable_unit(
+    value: Any,  # Allow invalid types for testing
+    unit: Any,  # Allow invalid types for testing
+    expected: Any,  # Allow invalid types for testing
+) -> None:
     """Test readable_unit function with valid inputs."""
     if isinstance(expected, type) and issubclass(expected, Exception):
         with pytest.raises(expected):