Fixed -p and improved coverage

tests/test_generator.py

@@ -1,5 +1,6 @@
 from os import remove
 from pathlib import Path
+from subprocess import run
 
 from PIL.Image import Image
 
@@ -28,6 +29,31 @@ def test_saving():
     remove(Path("tests/image.jpg"))
 
 
+def test_shell():
+    assert (
+        run(
+            [
+                "huepaper",
+                "-hue",
+                "0.3",
+                "-lmin",
+                "0.5",
+                "-lmax",
+                "0.3",
+                "-l",
+                "0.5",
+                "-p",
+                "64x36",
+                "-o",
+                "tests/image.jpg",
+            ],
+            check=False,
+        ).returncode
+        == 0
+    )
+    remove(Path("tests/image.jpg"))
+
+
 def test_generation_example_1():
     image = generate(color="lightgreen")
     assert isinstance(image, Image)