diff --git a/.dockerignore b/.dockerignore
index 83cee50..821c19d 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -1,2 +1 @@
-test/
 .github
\ No newline at end of file
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 50b4ba9..4a5cdbf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,6 +11,11 @@ jobs:
       - name: Checkout VCS
         uses: actions/checkout@v1
 
+      - name: 'Unit tests'
+        run: |
+          docker build --tag tests .
+          docker run --entrypoint python tests unit-tests.py
+
       - name: '[run] simple'
         uses: ./
         with:
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..52729dd
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,146 @@
+
+### Python ###
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+*.pyc
+
+
+
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+pip-wheel-metadata/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+pytestdebug.log
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+doc/_build/
+
+# PyBuilder
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+.python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+pythonenv*
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# profiling data
+.prof
+
+# End of https://www.toptal.com/developers/gitignore/api/python
diff --git a/Dockerfile b/Dockerfile
index 80afbfb..bb76dd3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -7,6 +7,6 @@ RUN poetry config virtualenvs.create false
 COPY poetry.lock pyproject.toml ./
 RUN poetry install
 
-COPY entrypoint.py ./entrypoint.py
+COPY . ./
 
 ENTRYPOINT ["./entrypoint.py"]
diff --git a/entrypoint.py b/entrypoint.py
index 8271a05..2a59afc 100755
--- a/entrypoint.py
+++ b/entrypoint.py
@@ -1,39 +1,12 @@
 #!/usr/bin/env python3
 
 import os
-from jinja2 import Template, StrictUndefined
-from j2cli.context import read_context_data
 
-def guess_format(file_name):
-    _, extension = os.path.splitext(file_name)
-    print(extension)
-    formats = {
-        '.yaml': 'yaml',
-        '.yml': 'yaml',
-        '.json': 'json',
-        '.ini': 'ini',
-        '.env': 'env',
-    }
-    return formats.get(extension, 'env')
+from main import Context
 
-variables = {'env': os.environ}
-for variable in os.environ.get('INPUT_VARIABLES', '').split('\n'):
-    clean_variable = bytes(variable.strip(), 'utf-8').decode('unicode_escape')
-    if clean_variable != '':
-        name, value = clean_variable.split('=', 1)
-        variables.update({name: value})
-
-data_file = os.environ.get('INPUT_DATA_FILE')
-if data_file:
-    format = os.environ.get('INPUT_DATA_FORMAT', guess_format(data_file))
-    with open(data_file, 'r') as file:
-        variables.update(read_context_data(format, file, None))
-
-with open(os.environ['INPUT_TEMPLATE'], 'r') as file:
-    template_kwargs = {}
-    if os.environ.get('INPUT_STRICT') == 'true':
-        template_kwargs.update({'undefined': StrictUndefined})
-    template = Template(str(file.read()), **template_kwargs)
-
-with open(os.environ['INPUT_OUTPUT_FILE'], 'w') as file:
-    file.write(template.render(**variables) + '\n')
+if __name__ == '__main__':
+    context = Context(os.environ)
+    context.load_from_env()
+    context.load_from_input()
+    context.load_from_data_file()
+    context.render_template()
diff --git a/enums.py b/enums.py
new file mode 100644
index 0000000..4915c07
--- /dev/null
+++ b/enums.py
@@ -0,0 +1,13 @@
+from enum import Enum
+
+
+class GitHubActionsInput(str, Enum):
+    DATA_FILE = 'INPUT_DATA_FILE'
+    DATA_FORMAT = 'INPUT_DATA_FORMAT'
+    OUTPUT_FILE = 'INPUT_OUTPUT_FILE'
+    STRICT = 'INPUT_STRICT'
+    TEMPLATE = 'INPUT_TEMPLATE'
+    VARIABLES = 'INPUT_VARIABLES'
+
+    def __str__(self):
+        return self.value
diff --git a/main.py b/main.py
new file mode 100644
index 0000000..e46e0f5
--- /dev/null
+++ b/main.py
@@ -0,0 +1,53 @@
+import os
+from j2cli.context import read_context_data
+from jinja2 import Template, StrictUndefined
+from enums import GitHubActionsInput
+
+class Context:
+    def __init__(self, environ):
+        self._variables = {}
+        self._environ = environ
+
+    def load_from_env(self):
+        self._variables.update({'env': self._environ})
+
+    def load_from_input(self):
+        for variable in self._environ.get(GitHubActionsInput.VARIABLES, '').split('\n'):
+            clean_variable = bytes(variable.strip(), 'utf-8').decode('unicode_escape')
+            if clean_variable != '':
+                name, value = clean_variable.split('=', 1)
+                self._variables.update({name: value})
+
+    def load_from_data_file(self):
+        data_file = self._environ.get(GitHubActionsInput.DATA_FILE)
+        if data_file:
+            format = self._environ.get(
+                GitHubActionsInput.DATA_FORMAT,
+                self._guess_format(data_file),
+            )
+            with open(data_file, 'r') as file:
+                self._variables.update(read_context_data(format, file, None))
+
+
+    def render_template(self):
+        with open(self._environ[GitHubActionsInput.TEMPLATE], 'r') as file:
+            template_kwargs = {}
+            if self._environ.get(GitHubActionsInput.STRICT) == 'true':
+                template_kwargs.update({'undefined': StrictUndefined})
+            template = Template(str(file.read()), **template_kwargs)
+
+        with open(self._environ[GitHubActionsInput.OUTPUT_FILE], 'w') as file:
+            file.write(template.render(**self._variables) + '\n')
+
+
+    def _guess_format(self, file_name):
+        _, extension = os.path.splitext(file_name)
+        formats = {
+            '.yaml': 'yaml',
+            '.yml': 'yaml',
+            '.json': 'json',
+            '.ini': 'ini',
+            '.env': 'env',
+        }
+        return formats.get(extension, 'env')
+
diff --git a/unit-tests.py b/unit-tests.py
new file mode 100644
index 0000000..43bb5f3
--- /dev/null
+++ b/unit-tests.py
@@ -0,0 +1,69 @@
+import os
+import unittest
+
+from enums import GitHubActionsInput
+from main import Context
+
+
+class TestContext(unittest.TestCase):
+    TEST_FILE = 'test_output'
+
+    def test_load_from_env(self):
+        env_vars = {
+            'foo': 'bar',
+            GitHubActionsInput.VARIABLES.value: 'name=John\nsurname=Doe'
+        }
+
+        context = Context(env_vars)
+        context.load_from_env()
+        expected = {'env': env_vars}
+        
+        self.assertEqual(context._variables, expected)
+
+    def test_load_from_input(self):
+        context = Context({GitHubActionsInput.VARIABLES.value: 'name=John\nsurname=Doe'})
+        context.load_from_input()
+
+        expected = {
+            'name': 'John',
+            'surname': 'Doe',
+        }
+        self.assertEqual(context._variables, expected)
+        
+
+    def test_load_from_data_file(self):
+        context = Context({
+            GitHubActionsInput.DATA_FILE.value: 'test/data-files/data.yml'
+        })
+
+        context.load_from_data_file()
+
+        expected = {
+            'foo': 'bar',
+            'baz': 'cux',
+        }
+        self.assertEqual(context._variables, expected)
+
+    def test_render_template(self):
+        context = Context({
+            GitHubActionsInput.DATA_FILE.value: 'test/data-files/data.json',
+            GitHubActionsInput.OUTPUT_FILE.value: self.TEST_FILE,
+            GitHubActionsInput.TEMPLATE.value: 'test/many-variables/template',
+        })
+        
+        context.load_from_data_file()
+        context.render_template()
+
+        expected = "\nbar\ncux\n"
+
+        with open('test_output', 'r') as file:
+            result = file.read()
+            self.assertEqual(result, expected)
+    
+    @classmethod
+    def tearDownClass(cls):
+        if os.path.exists(cls.TEST_FILE):
+            os.remove(cls.TEST_FILE)
+
+if __name__ == '__main__':
+    unittest.main()
\ No newline at end of file