test(agent): fix dead double-send in handleTraceRequest (#7725)

watson · web-flow · commit c8203349dfc7 · 2026-03-11T11:10:53.000-07:00
When the test agent returned a non-200 status, handleTraceRequest
attempted to call res.status(400).send() — but res.status(200).send()
had already been called synchronously earlier in the same function, so
the error response was silently dropped. Replace with a console.warn
so test agent errors are visible in CI logs instead of swallowed.

The res._closed guard is also removed since it only existed to protect
the now-removed res.status(400) call.
diff --git a/packages/dd-trace/test/plugins/agent.js b/packages/dd-trace/test/plugins/agent.js
@@ -200,19 +200,15 @@ function handleTraceRequest (req, res, sendToTestAgent) {
       })
 
     testAgentReq.on('response', testAgentRes => {
-      if (res._closed) {
-        // Skip handling for already closed agents
-        return
-      }
-
       if (testAgentRes.statusCode !== 200) {
         // handle request failures from the Test Agent here
         let body = ''
         testAgentRes.on('data', chunk => {
           body += chunk
         })
         testAgentRes.on('end', () => {
-          res.status(400).send(body)
+          // eslint-disable-next-line no-console
+          console.warn(`handleTraceRequest: Test agent returned ${testAgentRes.statusCode}: ${body}`)
         })
       }
     })
