feat: add resume support to coordinator connections (#14234)

testutil/ctx.go

@@ -23,6 +23,9 @@ func RequireRecvCtx[A any](ctx context.Context, t testing.TB, c <-chan A) (a A)
 	}
 }
 
+// NOTE: no AssertRecvCtx because it'd be bad if we returned a default value on
+// the cases it times out.
+
 func RequireSendCtx[A any](ctx context.Context, t testing.TB, c chan<- A, a A) {
 	t.Helper()
 	select {
@@ -32,3 +35,13 @@ func RequireSendCtx[A any](ctx context.Context, t testing.TB, c chan<- A, a A) {
 		// OK!
 	}
 }
+
+func AssertSendCtx[A any](ctx context.Context, t testing.TB, c chan<- A, a A) {
+	t.Helper()
+	select {
+	case <-ctx.Done():
+		t.Error("timeout")
+	case c <- a:
+		// OK!
+	}
+}