Add a failing test for detecting a file move

zed/src/test.rs

@@ -2,6 +2,7 @@ use rand::Rng;
 use std::{
     collections::BTreeMap,
     path::{Path, PathBuf},
+    time::{Duration, Instant},
 };
 use tempdir::TempDir;
 
@@ -136,3 +137,18 @@ fn write_tree(path: &Path, tree: serde_json::Value) {
         panic!("You must pass a JSON object to this helper")
     }
 }
+
+pub async fn assert_condition(poll_interval: u64, timeout: u64, mut f: impl FnMut() -> bool) {
+    let poll_interval = Duration::from_millis(poll_interval);
+    let timeout = Duration::from_millis(timeout);
+    let start = Instant::now();
+    loop {
+        if f() {
+            return;
+        } else if Instant::now().duration_since(start) < timeout {
+            smol::Timer::after(poll_interval).await;
+        } else {
+            panic!("timed out waiting on condition");
+        }
+    }
+}