making test more solid

src/LiveComponent/assets/test/controller/render.test.ts

@@ -365,6 +365,17 @@ describe('LiveController rendering Tests', () => {
             if (firstRenderFinishedAt === 0) {
                 firstRenderFinishedAt = Date.now();
             }
+
+            // the sleep guarantees that if the 2nd request was correctly
+            // delayed, its start time will be at least 10ms after the first
+            // render finished. Without this, even if the 2nd request is
+            // correctly delayed, the "first render finish" and "second render
+            // start" times could be the same, because no time has passed.
+            const sleep = (milliseconds: number) => {
+                const startTime = new Date().getTime();
+                while (new Date().getTime() < startTime + milliseconds);
+            }
+            sleep(10);
         });
 
         test.expectsAjaxCall();