Refactor infix processing in main test file

Added a preprocessing step for infix expressions to ensure consistent formatting before further processing. This change includes an assertion to validate the preprocessing output.

extras/tests/main.c

@@ -9,7 +9,10 @@
 
 int main(const int argc, char* argv[])
 {
- struct Oa_Expression* result = Oa_FromInFix("2 + 2");
+ const char* preprocessed = Oa_PreProcessInFix("2+2");
+ munit_assert_string_equal(preprocessed, "2 + 2");
+
+ struct Oa_Expression* result = Oa_FromInFix(preprocessed);
  munit_assert_not_null(result);
 
  const char* expected =