Initial release

Tests/KnotchyCoreTests/Support/Waiting.swift

@@ -0,0 +1,19 @@
+import Testing
+
+/// For work on other executors; controller timers run on the `TestClock` and never need it.
+@MainActor
+func waitUntil(
+    _ description: String,
+    timeout: Duration = .seconds(5),
+    sourceLocation: SourceLocation = #_sourceLocation,
+    _ condition: @MainActor () -> Bool
+) async {
+    let deadline = ContinuousClock.now + timeout
+    while !condition() {
+        if ContinuousClock.now >= deadline {
+            Issue.record("Timed out waiting until \(description)", sourceLocation: sourceLocation)
+            return
+        }
+        do { try await Task.sleep(for: .milliseconds(1)) } catch { return }
+    }
+}