Add test_argument_required

.editorconfig

@@ -9,3 +9,6 @@ charset = utf-8
 [*.py]
 indent_style = space
 indent_size = 2
+
+[Makefile]
+indent_size = tab

.gitignore

@@ -1,3 +1,5 @@
 .vscode
 dist
 src/*.egg-info
+__pycache__
+.pytest_cache

Makefile

@@ -0,0 +1,7 @@
+init:
+	pip install -r requirements.txt
+
+test:
+	py.test tests
+
+.PHONY: init test

manga_up/__main__.py

@@ -18,4 +18,4 @@ if __name__ == '__main__':
     '-n', '--notify', type=str, default=None, help="Apprise notification string."
   )
 
-args = parser.parse_args()
+  args = parser.parse_args()

tests/test_arguments.py

@@ -0,0 +1,12 @@
+from subprocess import CalledProcessError
+import unittest
+
+class FirstTestClass(unittest.TestCase):
+
+  def test_argument_required(self):
+    import subprocess
+    with self.assertRaises(CalledProcessError):
+      subprocess.check_output(['python', 'manga_up'])
+
+if __name__ == '__main__':
+  unittest.main()