test: faster test execution in codex-core (#2633)

this dramatically improves time to run `cargo test -p codex-core` (~25x
speedup).

before:
```
cargo test -p codex-core  35.96s user 68.63s system 19% cpu 8:49.80 total
```

after:
```
cargo test -p codex-core  5.51s user 8.16s system 63% cpu 21.407 total
```

both tests measured "hot", i.e. on a 2nd run with no filesystem changes,
to exclude compile times.

approach inspired by [Delete Cargo Integration
Tests](https://matklad.github.io/2021/02/27/delete-cargo-integration-tests.html),
we move all test cases in tests/ into a single suite in order to have a
single binary, as there is significant overhead for each test binary
executed, and because test execution is only parallelized with a single
binary.

codex-rs/mcp-server/tests/suite/login.rs

@@ -0,0 +1,146 @@
+use std::path::Path;
+use std::time::Duration;
+
+use codex_login::login_with_api_key;
+use codex_protocol::mcp_protocol::CancelLoginChatGptParams;
+use codex_protocol::mcp_protocol::CancelLoginChatGptResponse;
+use codex_protocol::mcp_protocol::GetAuthStatusParams;
+use codex_protocol::mcp_protocol::GetAuthStatusResponse;
+use codex_protocol::mcp_protocol::LoginChatGptResponse;
+use codex_protocol::mcp_protocol::LogoutChatGptResponse;
+use mcp_test_support::McpProcess;
+use mcp_test_support::to_response;
+use mcp_types::JSONRPCResponse;
+use mcp_types::RequestId;
+use tempfile::TempDir;
+use tokio::time::timeout;
+
+const DEFAULT_READ_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(10);
+
+// Helper to create a config.toml; mirrors create_conversation.rs
+fn create_config_toml(codex_home: &Path) -> std::io::Result<()> {
+    let config_toml = codex_home.join("config.toml");
+    std::fs::write(
+        config_toml,
+        r#"
+model = "mock-model"
+approval_policy = "never"
+sandbox_mode = "danger-full-access"
+
+model_provider = "mock_provider"
+
+[model_providers.mock_provider]
+name = "Mock provider for test"
+base_url = "http://127.0.0.1:0/v1"
+wire_api = "chat"
+request_max_retries = 0
+stream_max_retries = 0
+"#,
+    )
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn logout_chatgpt_removes_auth() {
+    let codex_home = TempDir::new().unwrap_or_else(|e| panic!("create tempdir: {e}"));
+    create_config_toml(codex_home.path()).expect("write config.toml");
+    login_with_api_key(codex_home.path(), "sk-test-key").expect("seed api key");
+    assert!(codex_home.path().join("auth.json").exists());
+
+    let mut mcp = McpProcess::new(codex_home.path())
+        .await
+        .expect("spawn mcp process");
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize())
+        .await
+        .expect("init timeout")
+        .expect("init failed");
+
+    let id = mcp
+        .send_logout_chat_gpt_request()
+        .await
+        .expect("send logoutChatGpt");
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(id)),
+    )
+    .await
+    .expect("logoutChatGpt timeout")
+    .expect("logoutChatGpt response");
+    let _ok: LogoutChatGptResponse = to_response(resp).expect("deserialize logout response");
+
+    assert!(
+        !codex_home.path().join("auth.json").exists(),
+        "auth.json should be deleted"
+    );
+
+    // Verify status reflects signed-out state.
+    let status_id = mcp
+        .send_get_auth_status_request(GetAuthStatusParams {
+            include_token: Some(true),
+            refresh_token: Some(false),
+        })
+        .await
+        .expect("send getAuthStatus");
+    let status_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(status_id)),
+    )
+    .await
+    .expect("getAuthStatus timeout")
+    .expect("getAuthStatus response");
+    let status: GetAuthStatusResponse = to_response(status_resp).expect("deserialize status");
+    assert_eq!(status.auth_method, None);
+    assert_eq!(status.auth_token, None);
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn login_and_cancel_chatgpt() {
+    let codex_home = TempDir::new().unwrap_or_else(|e| panic!("create tempdir: {e}"));
+    create_config_toml(codex_home.path()).expect("write config.toml");
+
+    let mut mcp = McpProcess::new(codex_home.path())
+        .await
+        .expect("spawn mcp process");
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize())
+        .await
+        .expect("init timeout")
+        .expect("init failed");
+
+    let login_id = mcp
+        .send_login_chat_gpt_request()
+        .await
+        .expect("send loginChatGpt");
+    let login_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(login_id)),
+    )
+    .await
+    .expect("loginChatGpt timeout")
+    .expect("loginChatGpt response");
+    let login: LoginChatGptResponse = to_response(login_resp).expect("deserialize login resp");
+
+    let cancel_id = mcp
+        .send_cancel_login_chat_gpt_request(CancelLoginChatGptParams {
+            login_id: login.login_id,
+        })
+        .await
+        .expect("send cancelLoginChatGpt");
+    let cancel_resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(cancel_id)),
+    )
+    .await
+    .expect("cancelLoginChatGpt timeout")
+    .expect("cancelLoginChatGpt response");
+    let _ok: CancelLoginChatGptResponse =
+        to_response(cancel_resp).expect("deserialize cancel response");
+
+    // Optionally observe the completion notification; do not fail if it races.
+    let maybe_note = timeout(
+        Duration::from_secs(2),
+        mcp.read_stream_until_notification_message("codex/event/login_chat_gpt_complete"),
+    )
+    .await;
+    if maybe_note.is_err() {
+        eprintln!("warning: did not observe login_chat_gpt_complete notification after cancel");
+    }
+}