Fix tests with outdated expectations

Author: mkArtakMSFT

src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

@@ -256,19 +256,13 @@ private void SetContentRoot(IWebHostBuilder builder)
             }
         }
 
-        if (contentRoot is null)
+        contentRoot ??= GetContentRootFromAssembly();
+        if (contentRoot is null || !Directory.Exists(contentRoot))
         {
-            contentRoot = GetContentRootFromAssembly();
+            contentRoot = AppContext.BaseDirectory;
         }
 
-        if (contentRoot is not null && Directory.Exists(contentRoot))
-        {
-            builder.UseContentRoot(contentRoot);
-        }
-        else
-        {
-            builder.UseContentRoot(AppContext.BaseDirectory);
-        }
+        builder.UseContentRoot(contentRoot);
     }
 
     private static string? GetContentRootFromFile(string file)

src/Mvc/test/Mvc.FunctionalTests/TestingInfrastructureInheritanceTests.cs

@@ -27,8 +27,13 @@ public void TestingInfrastructure_WebHost_WithWebHostBuilderRespectsCustomizatio
         Assert.Equal(new[] { "ConfigureWebHost", "Customization", "FurtherCustomization" }, factory.ConfigureWebHostCalled.ToArray());
         Assert.True(factory.CreateServerCalled);
         Assert.True(factory.CreateWebHostBuilderCalled);
-        // GetTestAssemblies is not called when reading content roots from MvcAppManifest
-        Assert.False(factory.GetTestAssembliesCalled);
+
+        // When run locally on the developer machine, the test manifest will be generated,
+        // and the content root will be read from the manifest file.
+        // However, when run in CI, the relative path in the metadata will not exist,
+        // and the content root lookup logic will probe the test assemblies too.
+        //Assert.False(factory.GetTestAssembliesCalled);
+
         Assert.True(factory.CreateHostBuilderCalled);
         Assert.False(factory.CreateHostCalled);
     }
@@ -45,7 +50,13 @@ public void TestingInfrastructure_GenericHost_WithWithHostBuilderRespectsCustomi
 
         // Assert
         Assert.Equal(new[] { "ConfigureWebHost", "Customization", "FurtherCustomization" }, factory.ConfigureWebHostCalled.ToArray());
-        Assert.False(factory.GetTestAssembliesCalled);
+
+        // When run locally on the developer machine, the test manifest will be generated,
+        // and the content root will be read from the manifest file.
+        // However, when run in CI, the relative path in the metadata will not exist,
+        // and the content root lookup logic will probe the test assemblies too.
+        //Assert.False(factory.GetTestAssembliesCalled);
+
         Assert.True(factory.CreateHostBuilderCalled);
         Assert.True(factory.CreateHostCalled);
         Assert.False(factory.CreateServerCalled);
@@ -128,7 +139,12 @@ public void Dispose()
 
     private class CustomizedFactory<TEntryPoint> : WebApplicationFactory<TEntryPoint> where TEntryPoint : class
     {
+        // GetTestAssemblies is not called when reading content roots from MvcAppManifest,
+        // and the content root specified in the manifest is a path that exists.
+        // Otherwise, the WebApplicationFactory will try to look for the referenced assemblies which have
+        // `WebApplicationFactoryContentRootAttribute` applied to them, to extract the content root path from that metadata.
         public bool GetTestAssembliesCalled { get; private set; }
+
         public bool CreateWebHostBuilderCalled { get; private set; }
         public bool CreateHostBuilderCalled { get; private set; }
         public bool CreateServerCalled { get; private set; }