Make ui test that are run-pass and do not test the compiler itself library tests

library/std/tests/thread.rs

@@ -0,0 +1,16 @@
+use std::sync::{Arc, Mutex};
+use std::thread;
+use std::time::Duration;
+
+#[test]
+#[cfg_attr(target_os = "emscripten", ignore)]
+fn sleep() {
+    let finished = Arc::new(Mutex::new(false));
+    let t_finished = finished.clone();
+    thread::spawn(move || {
+        thread::sleep(Duration::new(u64::MAX, 0));
+        *t_finished.lock().unwrap() = true;
+    });
+    thread::sleep(Duration::from_millis(100));
+    assert_eq!(*finished.lock().unwrap(), false);
+}