Add some argument parsing tests

And fix the one bug discovered in this process

repo2docker/__main__.py

@@ -1,6 +1,7 @@
 import argparse
 import sys
 import os
+import logging
 import docker
 from .app import Repo2Docker
 from . import __version__
@@ -251,8 +252,9 @@ def make_r2d(argv=None):
     r2d.push = args.push
 
     # check against r2d.run and not args.run as r2d.run is false on
-    # --no-build
-    if args.volumes and not r2d.run:
+    # --no-build. Also r2d.volumes and not args.volumes since --editable
+    # modified r2d.volumes
+    if r2d.volumes and not r2d.run:
         # Can't mount if we aren't running
         print('To Mount volumes with -v, you also need to run the '
                 'container')

tests/test_args.py

@@ -0,0 +1,64 @@
+"""
+Test argument parsing and r2d construction
+"""
+import os
+import pytest
+import logging
+from repo2docker.__main__ import make_r2d
+from repo2docker import __version__
+from contextlib import redirect_stdout
+import io
+
+def test_version():
+    """
+    Test passing '--version' to repo2docker
+    """
+    stdout = io.StringIO()
+    with redirect_stdout(stdout):
+        with pytest.raises(SystemExit):
+            make_r2d(['--version'])
+    assert stdout.getvalue().strip() == __version__
+
+def test_simple():
+    """
+    Test simplest possible invocation to r2d
+    """
+    r2d = make_r2d(['.'])
+    assert r2d.repo == '.'
+
+def test_editable():
+    """
+    Test --editable behavior
+    """
+    r2d = make_r2d(['--editable', '.'])
+    assert r2d.repo == '.'
+    assert r2d.volumes[os.getcwd()] == '.'
+
+def test_dry_run():
+    """
+    Test passing --no-build implies --no-run and lack of --push
+    """
+    r2d = make_r2d(['--no-build', '.'])
+    assert r2d.dry_run
+    assert not r2d.run
+    assert not r2d.push
+
+def test_run_required():
+    """
+    Test all the things that should fail if we pass in --no-run
+    """
+    # Can't use volumes without running
+    with pytest.raises(SystemExit):
+        make_r2d(['--no-run', '--editable', '.'])
+
+    # Can't publish all ports without running
+    with pytest.raises(SystemExit):
+        make_r2d(['--no-run', '-P', '.'])
+
+    # Can't publish any ports without running
+    with pytest.raises(SystemExit):
+        make_r2d(['--no-run', '-p', '8000:8000', '.'])
+
+    # Can't publish any ports while running if we don't specify a command explicitly
+    with pytest.raises(SystemExit):
+        make_r2d(['-p', '8000:8000', '.'])