ocamltest: opt-in -keep-test-dir-on-success to keep test data on success

ocamltest/main.ml

@@ -154,9 +154,11 @@ let test_file test_filename =
   let hookname_prefix = Filename.concat test_source_directory test_prefix in
   let test_build_directory_prefix =
     get_test_build_directory_prefix test_directory in
-  ignore (Sys.command ("rm -rf " ^ test_build_directory_prefix));
+  let clean_test_build_directory () =
+    ignore (Sys.command ("rm -rf " ^ test_build_directory_prefix)) in
+  clean_test_build_directory ();
   Sys.make_directory test_build_directory_prefix;
-  Sys.with_chdir test_build_directory_prefix
+  let summary = Sys.with_chdir test_build_directory_prefix
     (fun () ->
        let log =
          if !Options.log_to_stderr then stderr else begin
@@ -193,13 +195,20 @@ let test_file test_filename =
        let initial_status =
          if skip_test then Skip_all_tests else Run rootenv
        in
-       let _summary =
+       let summary =
          run_test_trees log common_prefix "" initial_status test_trees in
        Actions.clear_all_hooks();
-       if not !Options.log_to_stderr then close_out log
-    );
+       if not !Options.log_to_stderr then close_out log;
+       summary
+    ) in
   (* Restore current working directory  *)
-  Sys.chdir cwd
+  Sys.chdir cwd;
+  begin match summary with
+  | Some_failure -> ()
+  | No_failure ->
+      if not !Options.keep_test_dir_on_success then
+        clean_test_build_directory ()
+  end
 
 let is_test s =
   match tsl_block_of_file s with

ocamltest/options.ml

@@ -49,6 +49,8 @@ let log_to_stderr = ref false
 
 let promote = ref false
 
+let keep_test_dir_on_success = ref false
+
 let find_test_dirs = ref []
 
 let list_tests = ref []
@@ -68,6 +70,8 @@ let commandline_options =
    " Find directories that contain tests (recursive).");
   ("-list-tests", Arg.String (add_to_list list_tests),
    " List tests in given directory.");
+  ("-keep-test-dir-on-success", Arg.Set keep_test_dir_on_success,
+   " Keep the test directory (with the generated test artefacts) on success.");
 ]
 
 let files_to_test = ref []

ocamltest/options.mli

@@ -26,3 +26,5 @@ val usage : string
 val find_test_dirs : string list ref
 
 val list_tests : string list ref
+
+val keep_test_dir_on_success : bool ref