ViewStarts need to be executed as part of View execution

Fixes #834

samples/MvcSample.Web/MvcSample.Web.kproj

@@ -39,6 +39,7 @@
     <Content Include="Views\Shared\HelloWorldPartial.cshtml" />
     <Content Include="Views\Shared\MyView.cshtml" />
     <Content Include="Views\Shared\_Layout.cshtml" />
+    <Content Include="Views\_ViewStart.cshtml" />
     <Content Include="web.config" />
     <Content Include="web.Debug.config" />
     <Content Include="web.Release.config" />

samples/MvcSample.Web/Views/Shared/MyView.cshtml

@@ -1,7 +1,6 @@
 @using MvcSample.Web.Models
 @model User
 @{
-    Layout = "/Views/Shared/_Layout.cshtml";
     ViewBag.Title = "Home Page";
     string nullValue = null;
 

samples/MvcSample.Web/Views/Shared/_Layout.cshtml

@@ -27,12 +27,6 @@
     <div class="container body-content">
         @RenderBody()
         <hr />
-        <address>
-            @if (@Model != null)
-            {
-                @Model.Address
-            }
-        </address>
         <footer>
             <p>&copy; @DateTime.Now.Year - My ASP.NET Application</p>
         </footer>

samples/MvcSample.Web/Views/_ViewStart.cshtml

@@ -0,0 +1,3 @@
+@{
+    Layout = "/Views/Shared/_Layout.cshtml";
+}

src/Microsoft.AspNet.Mvc.Razor/IRazorPage.cs

@@ -16,6 +16,11 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// </summary>
         ViewContext ViewContext { get; set; }
 
+        /// <summary>
+        /// Gets the path to the page.
+        /// </summary>
+        string Path { get; set; }
+
         string BodyContent { get; set; }
 
         /// <summary>

src/Microsoft.AspNet.Mvc.Razor/IRazorPageFactory.cs

@@ -11,8 +11,8 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// <summary>
         /// Creates a <see cref="IRazorPage"/> for the specified path.
         /// </summary>
-        /// <param name="viewPath">The path to locate the RazorPage.</param>
+        /// <param name="path">The path to locate the page.</param>
         /// <returns>The IRazorPage instance if it exists, null otherwise.</returns>
-        IRazorPage CreateInstance(string viewPath);
+        IRazorPage CreateInstance(string path);
     }
 }

src/Microsoft.AspNet.Mvc.Razor/IViewStartProvider.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+
+namespace Microsoft.AspNet.Mvc.Razor
+{
+    /// <summary>
+    /// Defines methods for locating ViewStart pages that are applicable to a page.
+    /// </summary>
+    public interface IViewStartProvider
+    {
+        /// <summary>
+        /// Given a view path, returns a sequence of ViewStart instances
+        /// that are applicable to the specified view.
+        /// </summary>
+        /// <param name="path">The path of the page to locate ViewStart files for.</param>
+        /// <returns>A sequence of <see cref="IRazorPage"/> that represent ViewStart.</returns>
+        IEnumerable<IRazorPage> GetViewStartPages(string path);
+    }
+}

src/Microsoft.AspNet.Mvc.Razor/Microsoft.AspNet.Mvc.Razor.kproj

@@ -30,6 +30,9 @@
     <Compile Include="Compilation\RoslynCompilationService.cs" />
     <Compile Include="Extensions\DictionaryExtensions.cs" />
     <Compile Include="IRazorPage.cs" />
+    <Compile Include="IViewStartProvider.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="ViewStartProvider.cs" />
     <Compile Include="VirtualPathRazorPageFactory.cs" />
     <Compile Include="HelperResult.cs" />
     <Compile Include="IRazorPageActivator.cs" />

src/Microsoft.AspNet.Mvc.Razor/Properties/AssemblyInfo.cs

@@ -0,0 +1,6 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Microsoft.AspNet.Mvc.Razor.Test")]

src/Microsoft.AspNet.Mvc.Razor/RazorPage.cs

@@ -42,6 +42,9 @@ namespace Microsoft.AspNet.Mvc.Razor
             }
         }
 
+        /// <inheritdoc />
+        public string Path { get; set; }
+
         /// <inheritdoc />
         public ViewContext ViewContext { get; set; }
 

src/Microsoft.AspNet.Mvc.Razor/RazorView.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.IO;
+using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Mvc.Rendering;
@@ -17,6 +18,7 @@ namespace Microsoft.AspNet.Mvc.Razor
     {
         private readonly IRazorPageFactory _pageFactory;
         private readonly IRazorPageActivator _pageActivator;
+        private readonly IViewStartProvider _viewStartProvider;
         private readonly IRazorPage _page;
         private readonly bool _executeViewHierarchy;
 
@@ -30,11 +32,13 @@ namespace Microsoft.AspNet.Mvc.Razor
         /// view start and layout pages are executed as part of the executing the page.</param>
         public RazorView([NotNull] IRazorPageFactory pageFactory,
                          [NotNull] IRazorPageActivator pageActivator,
+                         [NotNull] IViewStartProvider viewStartProvider,
                          [NotNull] IRazorPage page,
                          bool executeViewHierarchy)
         {
             _pageFactory = pageFactory;
             _pageActivator = pageActivator;
+            _viewStartProvider = viewStartProvider;
             _page = page;
             _executeViewHierarchy = executeViewHierarchy;
         }
@@ -44,7 +48,7 @@ namespace Microsoft.AspNet.Mvc.Razor
         {
             if (_executeViewHierarchy)
             {
-                var bodyContent = await RenderPageAsync(_page, context);
+                var bodyContent = await RenderPageAsync(_page, context, executeViewStart: true);
                 await RenderLayoutAsync(context, bodyContent);
             }
             else
@@ -53,7 +57,9 @@ namespace Microsoft.AspNet.Mvc.Razor
             }
         }
 
-        private async Task<string> RenderPageAsync(IRazorPage page, ViewContext context)
+        private async Task<string> RenderPageAsync(IRazorPage page, 
+                                                   ViewContext context,
+                                                   bool executeViewStart)
         {
             var contentBuilder = new StringBuilder(1024);
             using (var bodyWriter = new StringWriter(contentBuilder))
@@ -64,6 +70,11 @@ namespace Microsoft.AspNet.Mvc.Razor
                 context.Writer = bodyWriter;
                 try
                 {
+                    if (executeViewStart)
+                    {
+                        // Execute view starts using the same context + writer as the page to render.
+                        await RenderViewStartAsync(context);
+                    }
                     await RenderPageCoreAsync(page, context);
                 }
                 finally
@@ -86,6 +97,19 @@ namespace Microsoft.AspNet.Mvc.Razor
             await page.ExecuteAsync();
         }
 
+        private async Task RenderViewStartAsync(ViewContext context)
+        {
+            var viewStarts = _viewStartProvider.GetViewStartPages(_page.Path);
+
+            foreach (var viewStart in viewStarts)
+            {
+                await RenderPageCoreAsync(viewStart, context);
+
+                // Copy over interesting properties from the ViewStart page to the entry page.
+                _page.Layout = viewStart.Layout;
+            }
+        }
+
         private async Task RenderLayoutAsync(ViewContext context,
                                              string bodyContent)
         {
@@ -104,7 +128,7 @@ namespace Microsoft.AspNet.Mvc.Razor
                 layoutPage.PreviousSectionWriters = previousPage.SectionWriters;
                 layoutPage.BodyContent = bodyContent;
 
-                bodyContent = await RenderPageAsync(layoutPage, context);
+                bodyContent = await RenderPageAsync(layoutPage, context, executeViewStart: false);
 
                 // Verify that RenderBody is called, or that RenderSection is called for all sections
                 layoutPage.EnsureBodyAndSectionsWereRendered();

src/Microsoft.AspNet.Mvc.Razor/RazorViewEngine.cs

@@ -28,12 +28,15 @@ namespace Microsoft.AspNet.Mvc.Razor
 
         private readonly IRazorPageFactory _pageFactory;
         private readonly IRazorPageActivator _viewActivator;
+        private readonly IViewStartProvider _viewStartProvider;
 
         public RazorViewEngine(IRazorPageFactory pageFactory,
-                               IRazorPageActivator viewActivator)
+                               IRazorPageActivator viewActivator,
+                               IViewStartProvider viewStartProvider)
         {
             _pageFactory = pageFactory;
             _viewActivator = viewActivator;
+            _viewStartProvider = viewStartProvider;
         }
 
         public IEnumerable<string> ViewLocationFormats
@@ -96,6 +99,7 @@ namespace Microsoft.AspNet.Mvc.Razor
         {
             var view = new RazorView(_pageFactory,
                                      _viewActivator,
+                                     _viewStartProvider,
                                      page, 
                                      executeViewHierarchy: !partial);
             return ViewEngineResult.Found(viewName, view);

src/Microsoft.AspNet.Mvc.Razor/ViewStartProvider.cs

@@ -0,0 +1,92 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using Microsoft.Framework.Runtime;
+
+namespace Microsoft.AspNet.Mvc.Razor
+{
+    /// <inheritdoc />
+    public class ViewStartProvider : IViewStartProvider
+    {
+        private const string ViewStartFileName = "_ViewStart.cshtml";
+        private readonly string _appRoot;
+        private readonly IRazorPageFactory _pageFactory;
+
+        public ViewStartProvider(IApplicationEnvironment appEnv,
+                                 IRazorPageFactory pageFactory)
+        {
+            _appRoot = TrimTrailingSlash(appEnv.ApplicationBasePath);
+            _pageFactory = pageFactory;
+        }
+
+        /// <inheritdoc />
+        public IEnumerable<IRazorPage> GetViewStartPages([NotNull] string path)
+        {
+            var viewStartLocations = GetViewStartLocations(path);
+            var viewStarts = viewStartLocations.Select(_pageFactory.CreateInstance)
+                                                .Where(p => p != null)
+                                                .ToArray();
+
+            // GetViewStartLocations return ViewStarts inside-out that is the _ViewStart closest to the page 
+            // is the first: e.g. [ /Views/Home/_ViewStart, /Views/_ViewStart, /_ViewStart ]
+            // However they need to be executed outside in, so we'll reverse the sequence.
+            Array.Reverse(viewStarts);
+
+            return viewStarts;
+        }
+
+        internal IEnumerable<string> GetViewStartLocations(string path)
+        {
+            if (string.IsNullOrEmpty(path))
+            {
+                return Enumerable.Empty<string>();
+            }
+
+            var viewStartLocations = new List<string>();
+            var currentDir = GetViewDirectory(_appRoot, path);
+            while (IsSubDirectory(_appRoot, currentDir))
+            {
+                viewStartLocations.Add(Path.Combine(currentDir, ViewStartFileName));
+                currentDir = Path.GetDirectoryName(currentDir);
+            }
+
+            return viewStartLocations;
+        }
+
+        private static bool IsSubDirectory(string appRoot, string currentDir)
+        {
+            return currentDir.StartsWith(appRoot, StringComparison.OrdinalIgnoreCase);
+        }
+
+        private static string GetViewDirectory(string appRoot, string viewPath)
+        {
+            if (viewPath.StartsWith("~/"))
+            {
+                viewPath = viewPath.Substring(2);
+            }
+            else if (viewPath[0] == Path.DirectorySeparatorChar || 
+                     viewPath[0] == Path.AltDirectorySeparatorChar)
+            {
+                viewPath = viewPath.Substring(1);
+            }
+
+            var viewDir = Path.GetDirectoryName(viewPath);
+            return Path.GetFullPath(Path.Combine(appRoot, viewDir));
+        }
+
+        private static string TrimTrailingSlash(string path)
+        {
+            if (path.Length > 0 &&
+                path[path.Length - 1] == Path.DirectorySeparatorChar)
+            {
+                return path.Substring(0, path.Length - 1);
+            }
+
+            return path;
+        }
+    }
+}

src/Microsoft.AspNet.Mvc.Razor/VirtualPathRazorPageFactory.cs

@@ -30,14 +30,15 @@ namespace Microsoft.AspNet.Mvc.Razor
         }
 
         /// <inheritdoc />
-        public IRazorPage CreateInstance([NotNull] string viewPath)
+        public IRazorPage CreateInstance([NotNull] string path)
         {
-            var fileInfo = _fileInfoCache.GetFileInfo(viewPath);
+            var fileInfo = _fileInfoCache.GetFileInfo(path);
 
             if (fileInfo != null)
             {
                 var result = _compilationService.Compile(fileInfo);
                 var page = (IRazorPage)_activator.CreateInstance(_serviceProvider, result.CompiledType);
+                page.Path = path;
                 return page;
             }
 

src/Microsoft.AspNet.Mvc/MvcServices.cs

@@ -43,6 +43,7 @@ namespace Microsoft.AspNet.Mvc
             yield return describe.Singleton<IViewEngineProvider, DefaultViewEngineProvider>();
             yield return describe.Scoped<ICompositeViewEngine, CompositeViewEngine>();
             yield return describe.Singleton<IRazorCompilationService, RazorCompilationService>();
+            yield return describe.Singleton<IViewStartProvider, ViewStartProvider>();
 
             yield return describe.Singleton<IRazorPageActivator, RazorPageActivator>();
             // Virtual path view factory needs to stay scoped so views can get get scoped services.

test/Microsoft.AspNet.Mvc.Razor.Test/Microsoft.AspNet.Mvc.Razor.Test.kproj

@@ -28,6 +28,7 @@
     <Compile Include="RazorPageTest.cs" />
     <Compile Include="RazorViewTest.cs" />
     <Compile Include="SpanFactory.cs" />
+    <Compile Include="ViewStartProviderTest.cs" />
   </ItemGroup>
   <Import Project="$(VSToolsPath)\AspNet\Microsoft.Web.AspNet.targets" Condition="'$(VSToolsPath)' != ''" />
 </Project>

test/Microsoft.AspNet.Mvc.Razor.Test/RazorViewEngineTest.cs

@@ -160,15 +160,35 @@ namespace Microsoft.AspNet.Mvc.Razor.Test
             }, result.SearchedLocations);
         }
 
+        [Fact]
+        public void FindView_ReturnsRazorView_IfLookupWasSuccessful()
+        {
+            // Arrange
+            var pageFactory = new Mock<IRazorPageFactory>();
+            pageFactory.Setup(p => p.CreateInstance(It.IsAny<string>()))
+                       .Returns(Mock.Of<IRazorPage>());
+            var viewEngine = new RazorViewEngine(pageFactory.Object,
+                                                 Mock.Of<IRazorPageActivator>(),
+                                                 Mock.Of<IViewStartProvider>());
+
+            // Act
+            var result = viewEngine.FindView(_controllerTestContext, "test-view");
+
+            // Assert
+            Assert.True(result.Success);
+            Assert.IsType<RazorView>(result.View);
+            Assert.Equal("/Views/bar/test-view.cshtml", result.ViewName);
+        }
+
         private IViewEngine CreateSearchLocationViewEngineTester()
         {
             var pageFactory = new Mock<IRazorPageFactory>();
             pageFactory.Setup(vpf => vpf.CreateInstance(It.IsAny<string>()))
                        .Returns<RazorPage>(null);
 
-            var pageActivator = Mock.Of<IRazorPageActivator>();
+            var viewEngine = new RazorViewEngine(pageFactory.Object,
-
+                                                 Mock.Of<IRazorPageActivator>(),
-            var viewEngine = new RazorViewEngine(pageFactory.Object, pageActivator);
+                                                 Mock.Of<IViewStartProvider>());
 
             return viewEngine;
         }

test/Microsoft.AspNet.Mvc.Razor.Test/RazorViewTest.cs

@@ -4,8 +4,8 @@
 using System;
 using System.IO;
 using System.Threading.Tasks;
-using Microsoft.AspNet.Http;
 using Microsoft.AspNet.Mvc.ModelBinding;
+using Microsoft.AspNet.PipelineCore;
 using Moq;
 using Xunit;
 
@@ -27,6 +27,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             });
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      Mock.Of<IRazorPageActivator>(),
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: false);
             var viewContext = CreateViewContext(view);
@@ -51,9 +52,10 @@ namespace Microsoft.AspNet.Mvc.Razor
                 Assert.Same(viewData, v.ViewContext.ViewData);
             });
             var activator = new Mock<IRazorPageActivator>();
-            
+
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      activator.Object,
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: false);
             var viewContext = CreateViewContext(view);
@@ -86,6 +88,7 @@ namespace Microsoft.AspNet.Mvc.Razor
                      .Verifiable();
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      activator.Object,
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: false);
             var viewContext = CreateViewContext(view);
@@ -98,15 +101,17 @@ namespace Microsoft.AspNet.Mvc.Razor
         }
 
         [Fact]
-        public async Task RenderAsync_WithoutHierarchy_DoesNotExecuteLayoutPages()
+        public async Task RenderAsync_WithoutHierarchy_DoesNotExecuteLayoutOrViewStartPages()
         {
             var page = new TestableRazorPage(v =>
             {
                 v.Layout = LayoutPath;
             });
             var pageFactory = new Mock<IRazorPageFactory>();
+            var viewStartProvider = CreateViewStartProvider();
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
+                                     viewStartProvider,
                                      page,
                                      executeViewHierarchy: false);
             var viewContext = CreateViewContext(view);
@@ -116,6 +121,7 @@ namespace Microsoft.AspNet.Mvc.Razor
 
             // Assert
             pageFactory.Verify(v => v.CreateInstance(It.IsAny<string>()), Times.Never());
+            Mock.Get(viewStartProvider).Verify(v => v.GetViewStartPages(It.IsAny<string>()), Times.Never());
         }
 
         [Fact]
@@ -129,6 +135,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             });
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      Mock.Of<IRazorPageActivator>(),
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: true);
             var viewContext = CreateViewContext(view);
@@ -152,6 +159,7 @@ namespace Microsoft.AspNet.Mvc.Razor
             });
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      Mock.Of<IRazorPageActivator>(),
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: true);
             var viewContext = CreateViewContext(view);
@@ -177,6 +185,49 @@ namespace Microsoft.AspNet.Mvc.Razor
                      .Verifiable();
             var view = new RazorView(Mock.Of<IRazorPageFactory>(),
                                      activator.Object,
+                                     CreateViewStartProvider(),
+                                     page,
+                                     executeViewHierarchy: true);
+            var viewContext = CreateViewContext(view);
+
+            // Act
+            await view.RenderAsync(viewContext);
+
+            // Assert
+            activator.Verify();
+        }
+
+        [Fact]
+        public async Task RenderAsync_WithHierarchy_ExecutesViewStart()
+        {
+            // Arrange
+            var actualLayoutPath = "";
+            var layoutPath = "/Views/_Shared/_Layout.cshtml";
+            var viewStart1 = new TestableRazorPage(v =>
+            {
+                v.Layout = "/fake-layout-path";
+            });
+            var viewStart2 = new TestableRazorPage(v =>
+            {
+                v.Layout = layoutPath;
+            });
+            var page = new TestableRazorPage(v =>
+            {
+                // This path must have been set as a consequence of running viewStart
+                actualLayoutPath = v.Layout;
+                // Clear out layout so we don't render it
+                v.Layout = null;
+            });
+            var activator = new Mock<IRazorPageActivator>();
+            activator.Setup(a => a.Activate(viewStart1, It.IsAny<ViewContext>()))
+                     .Verifiable();
+            activator.Setup(a => a.Activate(viewStart2, It.IsAny<ViewContext>()))
+                     .Verifiable();
+            activator.Setup(a => a.Activate(page, It.IsAny<ViewContext>()))
+                     .Verifiable();
+            var view = new RazorView(Mock.Of<IRazorPageFactory>(),
+                                     activator.Object,
+                                     CreateViewStartProvider(viewStart1, viewStart2),
                                      page,
                                      executeViewHierarchy: true);
             var viewContext = CreateViewContext(view);
@@ -231,6 +282,7 @@ foot-content";
 
             var view = new RazorView(pageFactory.Object,
                                      activator.Object,
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: true);
             var viewContext = CreateViewContext(view);
@@ -264,6 +316,7 @@ foot-content";
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: true);
             var viewContext = CreateViewContext(view);
@@ -290,6 +343,7 @@ foot-content";
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: true);
             var viewContext = CreateViewContext(view);
@@ -344,6 +398,7 @@ body-content";
 
             var view = new RazorView(pageFactory.Object,
                                      Mock.Of<IRazorPageActivator>(),
+                                     CreateViewStartProvider(),
                                      page,
                                      executeViewHierarchy: true);
             var viewContext = CreateViewContext(view);
@@ -357,8 +412,8 @@ body-content";
 
         private static ViewContext CreateViewContext(RazorView view)
         {
-            var httpContext = new Mock<HttpContext>();
+            var httpContext = new DefaultHttpContext();
-            var actionContext = new ActionContext(httpContext.Object, routeData: null, actionDescriptor: null);
+            var actionContext = new ActionContext(httpContext, routeData: null, actionDescriptor: null);
             return new ViewContext(
                 actionContext,
                 view,
@@ -366,6 +421,16 @@ body-content";
                 new StringWriter());
         }
 
+        private static IViewStartProvider CreateViewStartProvider(params IRazorPage[] viewStartPages)
+        {
+            viewStartPages = viewStartPages ?? new IRazorPage[0];
+            var viewStartProvider = new Mock<IViewStartProvider>();
+            viewStartProvider.Setup(v => v.GetViewStartPages(It.IsAny<string>()))
+                             .Returns(viewStartPages);
+
+            return viewStartProvider.Object;
+        }
+
         private class TestableRazorPage : RazorPage
         {
             private readonly Action<TestableRazorPage> _executeAction;

test/Microsoft.AspNet.Mvc.Razor.Test/ViewStartProviderTest.cs

@@ -0,0 +1,96 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.Diagnostics;
+using Microsoft.Framework.Runtime;
+using Moq;
+using Xunit;
+
+namespace Microsoft.AspNet.Mvc.Razor.Test
+{
+    public class ViewStartProviderTest
+    {
+        [Theory]
+        [InlineData(null)]
+        [InlineData("")]
+        public void GetViewStartLocations_ReturnsEmptySequenceIfViewPathIsEmpty(string viewPath)
+        {
+            // Arrange
+            var appPath = @"x:\test";
+            var provider = new ViewStartProvider(GetAppEnv(appPath), Mock.Of<IRazorPageFactory>());
+
+            // Act
+            var result = provider.GetViewStartLocations(viewPath);
+
+            // Assert
+            Assert.Empty(result);
+        }
+
+        public static IEnumerable<object[]> GetViewStartLocations_ReturnsPotentialViewStartLocationsData
+        {
+            get
+            {
+                yield return new object[]
+                {
+                    @"x:\test\myapp",
+                    "/Views/Home/View.cshtml",
+                    new[]
+                    {
+                        @"x:\test\myapp\Views\Home\_ViewStart.cshtml",
+                        @"x:\test\myapp\Views\_ViewStart.cshtml",
+                        @"x:\test\myapp\_ViewStart.cshtml",
+                    }
+                };
+
+                yield return new object[]
+                {
+                    @"x:\test\myapp",
+                    "Views/Home/View.cshtml",
+                    new[]
+                    {
+                        @"x:\test\myapp\Views\Home\_ViewStart.cshtml",
+                        @"x:\test\myapp\Views\_ViewStart.cshtml",
+                        @"x:\test\myapp\_ViewStart.cshtml",
+                    }
+                };
+
+                yield return new object[]
+                {
+                    @"x:\test\myapp\",
+                    "Views/Home/View.cshtml",
+                    new[]
+                    {
+                        @"x:\test\myapp\Views\Home\_ViewStart.cshtml",
+                        @"x:\test\myapp\Views\_ViewStart.cshtml",
+                        @"x:\test\myapp\_ViewStart.cshtml",
+                    }
+                };
+            }
+        }
+
+        [Theory]
+        [MemberData("GetViewStartLocations_ReturnsPotentialViewStartLocationsData")]
+        public void GetViewStartLocations_ReturnsPotentialViewStartLocations(string appPath,
+                                                                             string viewPath,
+                                                                             IEnumerable<string> expected)
+        {
+            // Arrange
+            var provider = new ViewStartProvider(GetAppEnv(appPath), Mock.Of<IRazorPageFactory>());
+
+            // Act
+            var result = provider.GetViewStartLocations(viewPath);
+
+            // Assert
+            Assert.Equal(expected, result);
+        }
+
+        private static IApplicationEnvironment GetAppEnv(string appPath)
+        {
+            var appEnv = new Mock<IApplicationEnvironment>();
+            appEnv.Setup(p => p.ApplicationBasePath)
+                  .Returns(appPath);
+            return appEnv.Object;
+        }
+    }
+}