Add first unit test so we can start collecting coverage

tests/pylorax/test_buildstamp.py

@@ -0,0 +1,23 @@
+import io
+import unittest
+from unittest.mock import patch
+
+from pylorax import buildstamp
+
+class BuildStampTestCase(unittest.TestCase):
+    def setUp(self):
+        self.bstamp = buildstamp.BuildStamp(
+            'Lorax Tests',
+            '0.1',
+            'https://github.com/rhinstaller/lorax/issues',
+            True,
+            'noarch'
+        )
+
+    def test_write_produces_file_with_expected_content(self):
+        out_file = io.StringIO()
+        with patch.object(out_file, 'close'):
+            with patch.object(buildstamp, 'open', return_value=out_file):
+                self.bstamp.write('/tmp/stamp.ini')
+                self.assertIn("[Main]\nProduct=Lorax Tests\nVersion=0.1\nBugURL=https://github.com/rhinstaller/lorax/issues\nIsFinal=True", out_file.getvalue())
+                self.assertIn("[Compose]\nLorax=devel", out_file.getvalue())