add generator integration test

Author: nllong

README.md

@@ -55,4 +55,8 @@ Check out our example Jupyter Notebook [here](https://nbviewer.jupyter.org/githu
 
 # Updating Version
 
-See the notes above on downloading and generating the new bsync.py file. 
+* See the notes above on downloading and generating the new bsync.py file. 
+* Bump version in `pyproject.toml` file
+* Add CHANGELOG entry
+* Update (or add) generator test in `.github/ci.yml`
+* Update this README with the latest version of testing.

tests/test_basic.py

@@ -0,0 +1,38 @@
+from lxml import etree
+import os
+from bsyncpy import bsync
+
+
+def test_writefile():
+    # remove old file
+    if os.path.exists("output.xml"):
+        os.remove("output.xml")
+    assert os.path.exists("output.xml") == False
+
+    # Create a root and set the version attribute
+    root = bsync.BuildingSync()
+    root.set("version", "2.4.0")
+
+    # Valid element attributes can also be passed in as kwargs
+    f = bsync.Facilities(bsync.Facilities.Facility(ID="Facility-42"))
+
+    # Add the facilities.facility elements to the root
+    root += f
+
+    # write the document to disk
+    with open("output.xml", "wb+") as f:
+        output = etree.tostring(
+            root.toxml(),
+            pretty_print=True,
+            doctype='<?xml version="1.0" encoding="UTF-8"?>',
+        )
+        f.write(output)
+
+    # verify that it is written out
+    assert os.path.exists("output.xml") == True
+
+    with open("output.xml") as f:
+        if '<BuildingSync version="2.4.0">' in f.read():
+            assert True
+        else:
+            assert False, "Could not find correct BuildingSync version in file"