schema_salad/tests: add tests for cli args testing: --version, empty args

- fix return condition in main()

Author: manu-chroma

schema_salad/main.py

@@ -87,7 +87,7 @@ def main(argsl=None):  # type: (List[str]) -> int
 
     if args.version is None and args.schema is None:
         print('%s: error: too few arguments' % sys.argv[0])
-        exit(0)
+        return 1
 
     if args.quiet:
         _logger.setLevel(logging.WARN)

schema_salad/tests/test_cli_args.py

@@ -0,0 +1,40 @@
+import unittest
+import sys
+
+import schema_salad.main as cli_parser
+
+""" for capturing print() output """
+from contextlib import contextmanager
+from StringIO import StringIO
+
+@contextmanager
+def captured_output():
+    new_out, new_err = StringIO(), StringIO()
+    old_out, old_err = sys.stdout, sys.stderr
+    try:
+        sys.stdout, sys.stderr = new_out, new_err
+        yield sys.stdout, sys.stderr
+    finally:
+        sys.stdout, sys.stderr = old_out, old_err
+
+
+""" test different sets of command line arguments"""
+class ParseCliArgs(unittest.TestCase):
+
+    def test_version(self):
+        args = [["--version"], ["-v"]]
+        for arg in args:
+            with captured_output() as (out, err):
+                cli_parser.main(arg)
+
+            response = out.getvalue().strip()  # capture output and strip newline
+            self.assertTrue("Current version" in response)
+
+    def test_empty_input(self):
+        # running schema_salad tool wihtout any args
+        args = []
+        with captured_output() as (out, err):
+            cli_parser.main(args)
+
+        response = out.getvalue().strip()
+        self.assertTrue("error: too few arguments" in response)