From 6c35e2e84d8c15dfcbd8ce38b3cc843f28ffccac Mon Sep 17 00:00:00 2001
From: Mackinnon Buck <mackinnon.buck@gmail.com>
Date: Thu, 6 Aug 2020 14:02:30 -0700
Subject: [PATCH] Fixed flaky test 'CanInfluenceHeadDuringPrerender'. (#24624)

---
 .../ServerExecutionTests/PrerenderingTest.cs  | 31 ++++++-------------
 .../PrerenderedHeadComponent.razor            | 16 ++++++++++
 2 files changed, 25 insertions(+), 22 deletions(-)

diff --git a/src/Components/test/E2ETest/ServerExecutionTests/PrerenderingTest.cs b/src/Components/test/E2ETest/ServerExecutionTests/PrerenderingTest.cs
index c049aa99f3..856740a65f 100644
--- a/src/Components/test/E2ETest/ServerExecutionTests/PrerenderingTest.cs
+++ b/src/Components/test/E2ETest/ServerExecutionTests/PrerenderingTest.cs
@@ -88,44 +88,31 @@ namespace Microsoft.AspNetCore.Components.E2ETest.ServerExecutionTests
         {
             Navigate("/prerendered/prerendered-head");
 
-            var metaWithBindings = Browser.FindElement(By.Id("meta-with-bindings"));
-            var metaNoBindings = Browser.FindElement(By.Id("meta-no-bindings"));
-
             // Validate updated head during prerender
             Browser.Equal("Initial title", () => Browser.Title);
-            Browser.Equal("Initial meta content", () => metaWithBindings.GetAttribute("content"));
-            Browser.Equal("Immutable meta content", () => metaNoBindings.GetAttribute("content"));
+            Browser.Equal("Initial meta content", () => GetMetaWithBindings().GetAttribute("content"));
+            Browser.Equal("Immutable meta content", () => GetMetaWithoutBindings().GetAttribute("content"));
 
             BeginInteractivity();
 
-            // Wait for elements to be recreated with internal ids to permit mutation
-            metaWithBindings = WaitForNewElement(metaWithBindings, "meta-with-bindings");
-            metaNoBindings = WaitForNewElement(metaNoBindings, "meta-no-bindings");
+            // Wait until the component has rerendered
+            Browser.Exists(By.Id("interactive-indicator"));
 
             // Validate updated head after prerender
             Browser.Equal("Initial title", () => Browser.Title);
-            Browser.Equal("Initial meta content", () => metaWithBindings.GetAttribute("content"));
-            Browser.Equal("Immutable meta content", () => metaNoBindings.GetAttribute("content"));
+            Browser.Equal("Initial meta content", () => GetMetaWithBindings().GetAttribute("content"));
+            Browser.Equal("Immutable meta content", () => GetMetaWithoutBindings().GetAttribute("content"));
 
             // Change parameter of meta component
             var inputMetaBinding = Browser.FindElement(By.Id("input-meta-binding"));
             inputMetaBinding.Clear();
             inputMetaBinding.SendKeys("Updated meta content\n");
 
-            // Wait for meta tag to be recreated with new attributes
-            metaWithBindings = WaitForNewElement(metaWithBindings, "meta-with-bindings");
-
             // Validate new meta content attribute
-            Browser.Equal("Updated meta content", () => metaWithBindings.GetAttribute("content"));
+            Browser.Equal("Updated meta content", () => GetMetaWithBindings().GetAttribute("content"));
 
-            IWebElement WaitForNewElement(IWebElement existingElement, string id)
-            {
-                var newElement = existingElement;
-
-                Browser.NotEqual(existingElement, () => newElement = Browser.FindElement(By.Id(id)) ?? newElement);
-
-                return newElement;
-            }
+            IWebElement GetMetaWithBindings() => Browser.FindElement(By.Id("meta-with-bindings"));
+            IWebElement GetMetaWithoutBindings() => Browser.FindElement(By.Id("meta-no-bindings"));
         }
 
         [Fact]
diff --git a/src/Components/test/testassets/BasicTestApp/PrerenderedHeadComponent.razor b/src/Components/test/testassets/BasicTestApp/PrerenderedHeadComponent.razor
index 7a879fc3fe..9ced4765eb 100644
--- a/src/Components/test/testassets/BasicTestApp/PrerenderedHeadComponent.razor
+++ b/src/Components/test/testassets/BasicTestApp/PrerenderedHeadComponent.razor
@@ -23,7 +23,23 @@
 
 <Meta id="meta-no-bindings" content="Immutable meta content" />
 
+@if (isInteractive)
+{
+    <span id="interactive-indicator">Interactive mode enabled.</span>
+}
+
 @code {
     private string title = "Initial title";
     private string metaContent = "Initial meta content";
+
+    private bool isInteractive;
+
+    protected override void OnAfterRender(bool firstRender)
+    {
+        if (firstRender)
+        {
+            isInteractive = true;
+            StateHasChanged();
+        }
+    }
 }