Add missing file, ignore output files

.gitignore

@@ -13,3 +13,5 @@ betterproto/tests/*.py
 dist
 **/*.egg-info
 output
+betterproto/tests/output_*
+.idea

betterproto/tests/generate.py

@@ -0,0 +1,31 @@
+#!/usr/bin/env python
+import os
+
+# Force pure-python implementation instead of C++, otherwise imports
+# break things because we can't properly reset the symbol database.
+os.environ["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = "python"
+
+
+from betterproto.tests.util import get_directories, protoc_plugin, protoc_reference, root_path
+
+def main():
+    os.chdir(root_path)
+    test_cases_directory = os.path.join(root_path, 'inputs')
+    test_case = get_directories(test_cases_directory)
+
+    for test_case_name in test_case:
+        test_case_path = os.path.join(test_cases_directory, test_case_name)
+
+        case_reference_output_dir = os.path.join(root_path, 'output_reference', test_case_name)
+        case_plugin_output_dir = os.path.join(root_path, 'output_betterproto', test_case_name)
+
+        print(f'Generating output for {test_case_name}')
+        os.makedirs(case_reference_output_dir, exist_ok=True)
+        os.makedirs(case_plugin_output_dir, exist_ok=True)
+
+        protoc_reference(test_case_path, case_reference_output_dir)
+        protoc_plugin(test_case_path, case_plugin_output_dir)
+
+
+if __name__ == "__main__":
+    main()