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/auth.rs

@@ -0,0 +1,142 @@
+use std::path::Path;
+
+use codex_login::login_with_api_key;
+use codex_protocol::mcp_protocol::AuthMode;
+use codex_protocol::mcp_protocol::GetAuthStatusParams;
+use codex_protocol::mcp_protocol::GetAuthStatusResponse;
+use mcp_test_support::McpProcess;
+use mcp_test_support::to_response;
+use mcp_types::JSONRPCResponse;
+use mcp_types::RequestId;
+use pretty_assertions::assert_eq;
+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 get_auth_status_no_auth() {
+    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 request_id = mcp
+        .send_get_auth_status_request(GetAuthStatusParams {
+            include_token: Some(true),
+            refresh_token: Some(false),
+        })
+        .await
+        .expect("send getAuthStatus");
+
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await
+    .expect("getAuthStatus timeout")
+    .expect("getAuthStatus response");
+    let status: GetAuthStatusResponse = to_response(resp).expect("deserialize status");
+    assert_eq!(status.auth_method, None, "expected no auth method");
+    assert_eq!(status.auth_token, None, "expected no token");
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn get_auth_status_with_api_key() {
+    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");
+
+    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 request_id = mcp
+        .send_get_auth_status_request(GetAuthStatusParams {
+            include_token: Some(true),
+            refresh_token: Some(false),
+        })
+        .await
+        .expect("send getAuthStatus");
+
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await
+    .expect("getAuthStatus timeout")
+    .expect("getAuthStatus response");
+    let status: GetAuthStatusResponse = to_response(resp).expect("deserialize status");
+    assert_eq!(status.auth_method, Some(AuthMode::ApiKey));
+    assert_eq!(status.auth_token, Some("sk-test-key".to_string()));
+    assert_eq!(status.preferred_auth_method, AuthMode::ChatGPT);
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn get_auth_status_with_api_key_no_include_token() {
+    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");
+
+    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");
+
+    // Build params via struct so None field is omitted in wire JSON.
+    let params = GetAuthStatusParams {
+        include_token: None,
+        refresh_token: Some(false),
+    };
+    let request_id = mcp
+        .send_get_auth_status_request(params)
+        .await
+        .expect("send getAuthStatus");
+
+    let resp: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await
+    .expect("getAuthStatus timeout")
+    .expect("getAuthStatus response");
+    let status: GetAuthStatusResponse = to_response(resp).expect("deserialize status");
+    assert_eq!(status.auth_method, Some(AuthMode::ApiKey));
+    assert!(status.auth_token.is_none(), "token must be omitted");
+    assert_eq!(status.preferred_auth_method, AuthMode::ChatGPT);
+}