fix: added test helpers for platform-specific paths (#7954)

This addresses post-merge feedback from
https://github.com/openai/codex/pull/7856.

codex-rs/core/tests/common/Cargo.toml

@@ -13,6 +13,7 @@ assert_cmd = { workspace = true }
 base64 = { workspace = true }
 codex-core = { workspace = true, features = ["test-support"] }
 codex-protocol = { workspace = true }
+codex-utils-absolute-path = { workspace = true }
 notify = { workspace = true }
 regex-lite = { workspace = true }
 serde_json = { workspace = true }

codex-rs/core/tests/common/lib.rs

@@ -6,7 +6,9 @@ use codex_core::CodexConversation;
 use codex_core::config::Config;
 use codex_core::config::ConfigOverrides;
 use codex_core::config::ConfigToml;
+use codex_utils_absolute_path::AbsolutePathBuf;
 use regex_lite::Regex;
+use std::path::PathBuf;
 
 #[cfg(target_os = "linux")]
 use assert_cmd::cargo::cargo_bin;
@@ -25,6 +27,49 @@ pub fn assert_regex_match<'s>(pattern: &str, actual: &'s str) -> regex_lite::Cap
         .unwrap_or_else(|| panic!("regex {pattern:?} did not match {actual:?}"))
 }
 
+pub fn test_path_buf_with_windows(unix_path: &str, windows_path: Option<&str>) -> PathBuf {
+    if cfg!(windows) {
+        if let Some(windows) = windows_path {
+            PathBuf::from(windows)
+        } else {
+            let mut path = PathBuf::from(r"C:\");
+            path.extend(
+                unix_path
+                    .trim_start_matches('/')
+                    .split('/')
+                    .filter(|segment| !segment.is_empty()),
+            );
+            path
+        }
+    } else {
+        PathBuf::from(unix_path)
+    }
+}
+
+pub fn test_path_buf(unix_path: &str) -> PathBuf {
+    test_path_buf_with_windows(unix_path, None)
+}
+
+pub fn test_absolute_path_with_windows(
+    unix_path: &str,
+    windows_path: Option<&str>,
+) -> AbsolutePathBuf {
+    AbsolutePathBuf::from_absolute_path(test_path_buf_with_windows(unix_path, windows_path))
+        .expect("test path should be absolute")
+}
+
+pub fn test_absolute_path(unix_path: &str) -> AbsolutePathBuf {
+    test_absolute_path_with_windows(unix_path, None)
+}
+
+pub fn test_tmp_path() -> AbsolutePathBuf {
+    test_absolute_path_with_windows("/tmp", Some(r"C:\Users\codex\AppData\Local\Temp"))
+}
+
+pub fn test_tmp_path_buf() -> PathBuf {
+    test_tmp_path().into_path_buf()
+}
+
 /// Returns a default `Config` whose on-disk state is confined to the provided
 /// temporary directory. Using a per-test directory keeps tests hermetic and
 /// avoids clobbering a developer’s real `~/.codex`.