Add test exercising actual CLI usage

.travis.yml

@@ -14,6 +14,7 @@ script:
   - python setup.py test
   - coverage run -m unittest discover
   - coverage report -m --include=pysyncdroid*
+  - bash tests/test_cli.sh
 
 after_success:
   - coveralls

tests/test_cli.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+# Install the package.
+python setup.py install
+
+ACTUAL_OUTPUT="$(pysyncdroid 2>&1)"
+EXPECTED_OUTPUT="usage: pysyncdroid [-h] -V VENDOR -M MODEL [-s SOURCE] [-d DESTINATION]
+                   [-f FILE] [-v] [-u {ignore,remove,synchronize}] [-o]
+                   [-i IGNORE_FILE_TYPE [IGNORE_FILE_TYPE ...]]
+pysyncdroid: error: the following arguments are required: -V/--vendor, -M/--model"
+
+if [ "$ACTUAL_OUTPUT" != "$EXPECTED_OUTPUT" ]
+then
+  echo "Unexpected 'pysyncdroid' output"
+  exit 1
+fi