Clean up 'inspector_break_on_first_line' test and fix its flakiness (d…

…enoland#5098)

cli/tests/inspector2.js

@@ -1 +1,4 @@
 console.log("hello from the script");
+
+// This process will be killed before the timeout is over.
+await new Promise((res, _) => setTimeout(res, 1000));

cli/tests/integration_tests.rs

@@ -2201,10 +2201,16 @@ async fn inspector_break_on_first_line() {
  .expect("Can't connect");
  assert_eq!(response.status(), 101); // Switching protocols.
 
- let (mut socket_tx, mut socket_rx) = socket.split();
+ let (mut socket_tx, socket_rx) = socket.split();
+ let mut socket_rx =
+ socket_rx.map(|msg| msg.unwrap().to_string()).filter(|msg| {
+ let pass = !msg.starts_with(r#"{"method":"Debugger.scriptParsed","#);
+ futures::future::ready(pass)
+ });
 
  let stdout = child.stdout.as_mut().unwrap();
- let mut stdout_lines = std::io::BufReader::new(stdout).lines();
+ let mut stdout_lines =
+ std::io::BufReader::new(stdout).lines().map(|r| r.unwrap());
 
  use TestStep::*;
  let test_steps = vec![
@@ -2230,20 +2236,8 @@ async fn inspector_break_on_first_line() {
 
  for step in test_steps {
  match step {
- StdOut(s) => match stdout_lines.next() {
- Some(Ok(line)) => assert_eq!(line, s),
- other => panic!(other),
- },
- WsRecv(s) => loop {
- let msg = match socket_rx.next().await {
- Some(Ok(msg)) => msg.to_string(),
- other => panic!(other),
- };
- if !msg.starts_with(r#"{"method":"Debugger.scriptParsed","#) {
- assert!(msg.starts_with(s));
- break;
- }
- },
+ StdOut(s) => assert_eq!(&stdout_lines.next().unwrap(), s),
+ WsRecv(s) => assert!(socket_rx.next().await.unwrap().starts_with(s)),
  WsSend(s) => socket_tx.send(s.into()).await.unwrap(),
  }
  }