test: reproduce #213

Re.Posix doesn't support character class

Signed-off-by: Rudi Grinberg <me@rgrinberg.com>

<!-- ps-id: e4ad97fe-6d31-411e-8a88-d1035a11592d -->

lib_test/dune

@@ -1,7 +1,7 @@
 (tests
  (libraries re fort_unit)
  (modules :standard \ test_str)
- (names test_easy test_re test_perl test_emacs test_glob test_pcre))
+ (names test_easy test_re test_perl test_emacs test_glob test_pcre test_posix))
 
 (test
  (libraries re fort_unit str)

lib_test/test_posix.ml

@@ -0,0 +1,13 @@
+open OUnit
+
+let test_class_space () =
+  match Re.Posix.compile_pat {|a[[:space:]]b|} with
+  | exception Re.Posix.Not_supported -> ()
+  | (_ : Re.re) -> assert false
+
+let suite = "posix" >:::
+  [ "regression 213" >:: test_class_space
+  ]
+
+let () =
+  ignore (run_test_tt_main suite)