Run tests on a random port

Before this patch, the `server` and `custom_ca_store` tests would run on
either port 1337 or 1338, but some other process could be using those
ports, which would confuse the results. This changes the tests to
instead use a random port in order to be more consistent.

Author: erickt

examples/server.rs

@@ -56,10 +56,11 @@ async fn run_server() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
     let key = PrivateKeyDer::from_pem_file("examples/sample.rsa")
         .map_err(|e| error(format!("could not read private key file: {e}")))?;
 
-    println!("Starting to serve on https://{addr}");
-
     // Create a TCP listener via tokio.
     let incoming = TcpListener::bind(&addr).await?;
+    let addr = incoming.local_addr()?;
+
+    println!("Starting to serve on https://{addr}");
 
     // Build TLS configuration.
     let mut server_config = ServerConfig::builder()

tests/tests.rs

@@ -1,9 +1,8 @@
 use std::env;
-use std::net::TcpStream;
+use std::io::{BufRead, BufReader};
+use std::net::SocketAddr;
 use std::path::PathBuf;
-use std::process::Command;
-use std::thread;
-use std::time;
+use std::process::{Child, Command, Stdio};
 
 fn examples_dir() -> PathBuf {
     let target_dir: PathBuf = env::var("CARGO_TARGET_DIR")
@@ -18,18 +17,37 @@ fn server_command() -> Command {
     Command::new(examples_dir().join("server"))
 }
 
-fn client_command() -> Command {
-    Command::new(examples_dir().join("client"))
+fn start_server() -> (Child, SocketAddr) {
+    let mut srv = server_command()
+        .arg("0")
+        .stdout(Stdio::piped())
+        .stderr(Stdio::inherit())
+        .spawn()
+        .expect("cannot run server example");
+
+    let stdout = srv
+        .stdout
+        .take()
+        .expect("failed to get stdout");
+
+    let mut reader = BufReader::new(stdout);
+    let mut line = String::new();
+    reader
+        .read_line(&mut line)
+        .expect("failed to read line");
+
+    let addr = line
+        .trim()
+        .strip_prefix("Starting to serve on https://")
+        .expect("unexpected output")
+        .parse()
+        .expect("failed to parse socket address");
+
+    (srv, addr)
 }
 
-fn wait_for_server(addr: &str) {
-    for i in 0..10 {
-        if TcpStream::connect(addr).is_ok() {
-            return;
-        }
-        thread::sleep(time::Duration::from_millis(i * 100));
-    }
-    panic!("failed to connect to {addr:?} after 10 tries");
+fn client_command() -> Command {
+    Command::new(examples_dir().join("client"))
 }
 
 #[test]
@@ -44,18 +62,12 @@ fn client() {
 
 #[test]
 fn server() {
-    let mut srv = server_command()
-        .arg("1337")
-        .spawn()
-        .expect("cannot run server example");
-
-    let addr = "localhost:1337";
-    wait_for_server(addr);
+    let (mut srv, addr) = start_server();
 
     let output = Command::new("curl")
         .arg("--insecure")
         .arg("--http1.0")
-        .arg(format!("https://{addr}"))
+        .arg(format!("https://localhost:{}", addr.port()))
         .output()
         .expect("cannot run curl");
 
@@ -78,16 +90,10 @@ fn server() {
 
 #[test]
 fn custom_ca_store() {
-    let mut srv = server_command()
-        .arg("1338")
-        .spawn()
-        .expect("cannot run server example");
-
-    let addr = "localhost:1338";
-    wait_for_server(addr);
+    let (mut srv, addr) = start_server();
 
     let rc = client_command()
-        .arg(format!("https://{addr}"))
+        .arg(format!("https://localhost:{}", addr.port()))
         .arg("examples/sample.pem")
         .output()
         .expect("cannot run client example");