test: check if destination exists

manga_up/__main__.py

@@ -3,6 +3,7 @@ Manga checker and downloader
 """
 
 import argparse
+import os
 
 if __name__ == '__main__':
   parser = argparse.ArgumentParser(
@@ -19,3 +20,10 @@ if __name__ == '__main__':
   )
 
   args = parser.parse_args()
+
+  destination = os.path.abspath(args.destination)
+
+  if not os.path.exists(destination):
+    print(f'Destination {destination} does not exist.')
+  if not os.path.isdir(destination):
+    print(f'Destination {destination} is not a directory.')

tests/test_arguments.py

@@ -1,12 +1,29 @@
 from subprocess import CalledProcessError
 import unittest
+import subprocess
+import os
 
-class FirstTestClass(unittest.TestCase):
+
+class ArgumentTestClass(unittest.TestCase):
+
+  def setUp(self):
+    import tempfile
+    self.existing_dir = tempfile.mkdtemp()
 
   def test_argument_required(self):
-    import subprocess
     with self.assertRaises(CalledProcessError):
       subprocess.check_output(['python', 'manga_up'])
 
+  def test_destination_exists(self):
+    result = subprocess.check_output(['python', 'manga_up', '--destination', 'nonexistent'])
+    self.assertIn('does not exist', str(result))
+
+  def test_destination_is_not_directory(self):
+    result = subprocess.check_output(['python', 'manga_up', '--destination', self.existing_file])
+    self.assertIn('not a directory', str(result))
+
+  def tearDown(self) -> None:
+      os.rmdir(self.existing_dir)
+
 if __name__ == '__main__':
   unittest.main()