fix(tests/explorer/new_folder): failing on Windows

Co-authored-by: LEI <github@lei.sh>
Reference: https://github.com/helix-editor/helix/pull/5768#discussion_r1143991188

helix-term/src/ui/explorer.rs

@@ -994,17 +994,22 @@ mod test_explorer {
         // 0. Open the add file/folder prompt
         explorer.handle_events("a").unwrap();
         let prompt = &explorer.prompt.as_ref().unwrap().1;
-        fn sanitize(s: &str) -> String {
+        fn to_forward_slash(s: &str) -> String {
             s.replace(std::path::MAIN_SEPARATOR, "/")
         }
+        fn to_os_main_separator(s: &str) -> String {
+            s.replace('/', format!("{}", std::path::MAIN_SEPARATOR).as_str())
+        }
         assert_eq!(
-            sanitize(&prompt.prompt()),
+            to_forward_slash(&prompt.prompt()),
             " New file or folder (ends with '/'): "
         );
-        assert_eq!(sanitize(prompt.line()), "test_explorer/new_folder/");
+        assert_eq!(to_forward_slash(prompt.line()), "test_explorer/new_folder/");
 
         // 1. Add a new folder at the root
-        explorer.handle_events(&sanitize("yoyo/<ret>")).unwrap();
+        explorer
+            .handle_events(&to_os_main_separator("yoyo/<ret>"))
+            .unwrap();
 
         // 1a. Expect the new folder is added, and is focused
         assert_eq!(
@@ -1027,7 +1032,7 @@ mod test_explorer {
 
         // 3. Add a new folder
         explorer
-            .handle_events(&sanitize("asus.sass/<ret>"))
+            .handle_events(&to_os_main_separator("asus.sass/<ret>"))
             .unwrap();
 
         // 3a. Expect the new folder is added under "styles", although "styles" is not opened
@@ -1050,7 +1055,9 @@ mod test_explorer {
         assert!(fs::read_dir(path.join("styles/sus.sass")).is_ok());
 
         // 4. Add a new folder with non-existent parents
-        explorer.handle_events(&sanitize("aa/b/c/<ret>")).unwrap();
+        explorer
+            .handle_events(&to_os_main_separator("aa/b/c/<ret>"))
+            .unwrap();
 
         // 4a. Expect the non-existent parents are created,
         //     and the new folder is created,
@@ -1078,7 +1085,9 @@ mod test_explorer {
         explorer.handle_events("j").unwrap();
 
         // 6. Add a new folder here
-        explorer.handle_events(&sanitize("afoobar/<ret>")).unwrap();
+        explorer
+            .handle_events(&to_os_main_separator("afoobar/<ret>"))
+            .unwrap();
 
         // 6a. Expect the folder is added under "styles",
         //     because the folder of the current item, "style.css" is "styles/"