Changed to google style docstrings. Added image_name validation test.

repo2docker/app.py

@@ -124,10 +124,18 @@ class Repo2Docker(Application):
 
     def validate_image_name(self, image_name):
         """
-        Validate that the image_name read by argparse contains only lowercase characters
-        :param image_name: string argument read by argparse
-        :return: test and return image_name if it only contains lowercase characters else raise error
+        Validate image_name read by argparse contains only lowercase characters
+
+        Args:
+            image_name: string argument read by the argument parser
+
+        Returns:
+            unmodified image_name
+
+        Raises:
+            ArgumentTypeError: if image_name contains characters that are not lowercase
         """
+
         if not image_name.islower():
             msg = "%r is not a valid docker image name. Image name can contain only lowercase characters." % image_name
             raise argparse.ArgumentTypeError(msg)

tests/argumentvalidation.py

@@ -0,0 +1,35 @@
+"""
+Tests that runs validity checks on arguments passed in from shell
+"""
+
+import os
+import subprocess
+
+def does_validate_image_name(builddir, image_name):
+    try:
+        output = subprocess.check_output(
+            [
+                'repo2docker',
+                '--no-run',
+                '--image-name',
+                str(image_name),
+                builddir
+            ],
+            stderr=subprocess.STDOUT,
+        ).decode()
+        print(output)
+        return True
+    except subprocess.CalledProcessError as e:
+        output = e.output.decode()
+        print(output)
+        if "error: argument --image-name: %r is not a valid docker image name. " \
+           "Image name can contain only lowercase characters." % image_name in output:
+            return False
+        else:
+            raise
+
+def test_image_name_fail():
+    builddir = os.path.dirname(__file__)
+
+    assert not does_validate_image_name(builddir, 'Test/Invalid_name:1.0.0')
+