diff --git a/tests/files/test1/test.mo.env b/tests/files/test1/test.mo.env
new file mode 100644
index 0000000..e3b4cb0
--- /dev/null
+++ b/tests/files/test1/test.mo.env
@@ -0,0 +1,7 @@
+value=${sample}
+nested=${some/nested/value}
+mixed=${some/nested/value.username}
+custom=${custom.field}
+
+uname=${sample.username}
+invalid=${double.dot.example}
diff --git a/tests/test_mo_env.py b/tests/test_mo_env.py
new file mode 100644
index 0000000..bbbf0da
--- /dev/null
+++ b/tests/test_mo_env.py
@@ -0,0 +1,64 @@
+from pathlib import Path
+
+import pytest
+import yaml
+
+from karl.services import Passwords
+from karl.services.mo import Mo
+
+
+@pytest.fixture(scope='class')
+def target_path():
+  # p = Path('tests/files/test1/test.env')
+  p = Path('files/test1/test.env')
+  # posprzątaj przed testem, gdyby plik istniał z poprzednich uruchomień
+  if p.exists():
+    p.unlink()
+  yield p
+  # sprzątanie po teście
+  if p.exists():
+    p.unlink()
+
+
+@pytest.fixture(scope='class')
+def test1_content(target_path: Path):
+  mo = Mo(Passwords())
+  mo.process(Path('files/test1/test.mo.env').absolute())
+  # mo.process(Path('tests/files/test1/test.mo.env').absolute())
+
+  assert target_path.absolute().exists()
+
+  content = target_path.read_text()
+  assert '${' not in content
+
+
+  props = {}
+  prop_lines = content.split('\n')
+  for line in prop_lines:
+    if len(line)> 1:
+      splitted = line.split('=')
+      props[splitted[0]] = splitted[1]
+  # props = {prop[0]:prop[1] for prop in content.split('\n')}
+  print(props)
+  yield props
+
+
+class TestEnvParsing:
+
+  def test_simple(self, test1_content: dict):
+    assert test1_content['value'] == 'some_pass'
+
+  def test_nested(self, test1_content: dict):
+    assert test1_content['nested'] == 'nested_pass'
+
+  def test_mixed(self, test1_content: dict):
+    assert test1_content['mixed'] == 'nested_username'
+
+  def test_custom_field(self, test1_content: dict):
+    assert test1_content['custom'] == 'custom_content'
+
+  def test_username_field(self, test1_content: dict):
+    assert test1_content['uname'] == 'sample_username'
+
+  def test_invalid_key(self, test1_content: dict):
+    assert test1_content.get('invalid') == 'None'