message: Remove a magic string from tests of diagnostics console
diff: @@ -187,6 +187,8 @@ mod tests {
  #[tokio::test]
  async fn setup_listener_creates_listener() {
  + const TEST_MESSAGE: &[u8] = b"hello, world!";
  +
  let tmpdir = tempfile::tempdir().expect("could not create tempdir");
  let socket_path = tmpdir.path().join("test.socket");
  @@ -203,7 +205,7 @@ mod tests {
  .await
  .expect("could not connect to listener");
  stream
  - .write_all(b"hello")
  + .write_all(TEST_MESSAGE)
  .await
  .expect("could not write to listener");
  });
  @@ -218,7 +220,7 @@ mod tests {
  .read_to_end(&mut buffer)
  .await
  .expect("failed to read to end");
  - assert_eq!(b"hello", buffer.as_slice());
  + assert_eq!(TEST_MESSAGE, buffer.as_slice());
  }
  #[tokio::test]
  