1 files changed, 17 insertions, 1 deletions
diff --git a/std/http/io_test.ts b/std/http/io_test.ts
index 7261964d0..c1d6a921b 100644
--- a/std/http/io_test.ts
+++ b/std/http/io_test.ts
@@ -5,6 +5,7 @@ import {
   assert,
   assertNotEOF,
   assertNotEquals,
+  assertMatch,
 } from "../testing/asserts.ts";
 import {
   bodyReader,
@@ -349,13 +350,28 @@ malformedHeader
 `;
   const reader = new BufReader(new StringReader(input));
   let err;
+  let responseString: string;
   try {
-    await readRequest(mockConn(), reader);
+    // Capture whatever `readRequest()` attempts to write to the connection on
+    // error. We expect it to be a 400 response.
+    await readRequest(
+      mockConn({
+        write(p: Uint8Array): Promise<number> {
+          responseString = decode(p);
+          return Promise.resolve(p.length);
+        },
+      }),
+      reader
+    );
   } catch (e) {
     err = e;
   }
   assert(err instanceof Error);
   assertEquals(err.message, "malformed MIME header line: malformedHeader");
+  assertMatch(
+    responseString!,
+    /^HTTP\/1\.1 400 Bad Request\r\ncontent-length: \d+\r\n\r\n.*\r\n\r\n$/ms
+  );
 });
 
 // Ported from Go