test(rust): drop the raw-hyper_util duplicate of the 2xx-not-200 tripwire

hyper_util_still_refuses_a_2xx_that_is_not_200 (tests/upstream_tunnel.rs) called Tunnel
directly, with none of this crate's own code involved, to pin the same known defect
known_issue_a_success_other_than_200_does_not_open_the_tunnel (tests/proxy.rs) already pins
through the full stack - config, connect, ProxyConnector, translate(). Both go red the day
hyper-util fixes it; the proxy.rs one is strictly more informative, since it also proves this
crate's own error translation still reacts correctly. Kept that one, dropped the raw
duplicate.

The other two tests in upstream_tunnel.rs stay: the control, and the split-status-line case,
which has no equivalent in tests/proxy.rs.

Updated the file's module doc and the remaining test's panic message, which both referenced
the removed test. Corrected the README's "Known issues" intro, which claimed every pinning
test is named known_issue_*: the upstream_tunnel.rs ones never were.

Author: wkirschenmann

packages/rust/armonik-transport/README.md

@@ -22,8 +22,9 @@ out in the clear, the proxy's own URL has to be `http`. The tunnel handshake its
 ### Known issues
 
 `Tunnel`, as shipped in `hyper-util` 0.1.20, gets four cases wrong. None are ours to fix directly, and
-each is pinned by a test named `known_issue_*`, in `tests/proxy.rs` or `tests/upstream_tunnel.rs`, so a
-`hyper-util` release that fixes one turns that test red rather than letting the fix pass unnoticed.
+each is pinned by a test - named `known_issue_*` in `tests/proxy.rs`, or named for what it exercises in
+`tests/upstream_tunnel.rs` - so a `hyper-util` release that fixes one turns that test red rather than
+letting the fix pass unnoticed.
 
 - **Only an exact `200` opens the tunnel.** RFC 9110 says any `2xx` should. A proxy answering `201` or
   `204` is treated as a refusal.

packages/rust/armonik-transport/tests/upstream_tunnel.rs

@@ -1,9 +1,8 @@
 //! What `hyper_util`'s `Tunnel`, which [`crate::proxy`] drives, still gets wrong.
 //!
-//! These tests assert that `Tunnel` gets two cases wrong. They are meant to fail: when a
-//! `hyper-util` release fixes either, the failure is the notice that the crate README's
-//! "Known issues" section, and the matching tripwire in `tests/proxy.rs`, are out of date.
-//! Fixing them upstream is tracked by #702.
+//! This asserts that `Tunnel` gets a split status line wrong. It is meant to fail: when a
+//! `hyper-util` release fixes it, the failure is the notice that the crate README's "Known issues"
+//! section is out of date. Fixing it upstream is tracked by #702.
 //!
 //! A dependency bump turning CI red is the point. Read the failure before assuming it is a regression.
 
@@ -94,26 +93,6 @@ async fn a_plain_200_opens_the_tunnel() {
         .expect("the fixture itself must let an ordinary 200 through");
 }
 
-#[tokio::test]
-async fn hyper_util_still_refuses_a_2xx_that_is_not_200() {
-    // RFC 9110: any 2xx switches a `CONNECT` connection to tunnel mode. `Tunnel` compares the status
-    // line against `200` alone, so a proxy answering 201 is treated as a refusal.
-    let proxy = spawn_proxy("HTTP/1.1 201 Connection established\r\n\r\n", None).await;
-
-    let error = tunnel_through(proxy).await.err().unwrap_or_else(|| {
-        panic!(
-            "hyper-util now opens the tunnel on a 2xx other than 200. \
-             Check the split-status-line case too, and if that is fixed as well, drop this test, \
-             the matching one in tests/proxy.rs, and the README's \"Known issues\" section."
-        )
-    });
-
-    assert!(
-        error.contains("unsuccessful"),
-        "unexpected failure: {error}"
-    );
-}
-
 #[tokio::test]
 async fn hyper_util_still_refuses_a_status_line_split_across_reads() {
     // Cut inside `HTTP/1.1 200`, so the first read carries `HTTP/1.1 2`, which matches neither prefix
@@ -125,8 +104,7 @@ async fn hyper_util_still_refuses_a_status_line_split_across_reads() {
         panic!(
             "hyper-util now reads a split status line correctly, or the two writes reached it as \
              one read. Rule the second out before believing the first: the halves are 50ms apart \
-             on a socket with Nagle off. If it really is fixed, check the 2xx case too, and if that \
-             is fixed as well, drop this test, the matching one in tests/proxy.rs, and the README's \
+             on a socket with Nagle off. If it really is fixed, drop this test and the README's \
              \"Known issues\" section."
         )
     });