Changed the ast flag to --print-ast and properly save pretty-printed input files

mjtest/environment.py

@@ -106,7 +106,7 @@ class Environment:
         mode_flag = {
             TestMode.lexer: "--lextest",
             TestMode.syntax: "--parsetest",
-            TestMode.ast: "--pretty-print"
+            TestMode.ast: "--print-ast"
         }[mode]
         cmd = [self.mj_run_cmd, mode_flag] + list(args)
         return execute(cmd, timeout=self.timeout)
@@ -117,4 +117,4 @@ class Environment:
 
         :return: (out, err, return code)
         """
-        return execute([cmd] + list(args), timeout=self.timeout)
\ No newline at end of file
+        return execute([cmd] + list(args), timeout=self.timeout)

mjtest/test/ast_tests.py

@@ -85,8 +85,8 @@ class ASTPrettyPrintTest(BasicSyntaxTest):
 
     def _pretty_print(self, input_file: str, output_file: str) -> Tuple[int, str, str]:
         out, err, rtcode = self.env.run_mj_command(TestMode.ast, input_file)
-        with open(output_file, "w") as f:
-            print(out, file=f)
+        with open(output_file, "wb") as f:
+            f.write(out)
         return rtcode, out.decode(), err.decode()
 
-TestCase.TEST_CASE_CLASSES["ast"].append(ASTPrettyPrintTest)
\ No newline at end of file
+TestCase.TEST_CASE_CLASSES["ast"].append(ASTPrettyPrintTest)