Add a test for parse error output (coverage)

Author: dbanty

end_to_end_tests/invalid_openapi.yaml

@@ -0,0 +1,3 @@
+openapi:
+  info:
+    title: "I don't have a version"

end_to_end_tests/test_end_to_end.py

@@ -222,6 +222,13 @@ def test_bad_url():
     assert "Could not get OpenAPI document from provided URL" in result.stdout
 
 
+def test_invalid_document():
+    runner = CliRunner()
+    result = runner.invoke(app, ["generate", "--path=end_to_end_tests/invalid_openapi.yaml"])
+    assert result.exit_code == 1
+    assert "Failed to parse OpenAPI document" in result.stdout
+
+
 def test_custom_post_hooks():
     shutil.rmtree(Path.cwd() / "my-test-api-client", ignore_errors=True)
     runner = CliRunner()