# Getting TAEF unittests to work with a C++/WinRT XAML Islands application

* __Author__: Mike Griese @zadjii-msft
* __Created on__: 2019-06-06


So you've built a Win32 application that uses XAML Islands to display it's UI
with C++/WinRT. How do you go about adding unittests to this application? I'm
going to cover the steps that I took to get the Windows Terminal updated to be
able to test not only our C++/WinRT components, but also pure c++ classes that
were used in the application, and components that used XAML UI elements.

## Prerequisites

Make sure you're using at least the 2.0.190605.7 version of the CppWinRT nuget
package. Prior to this version, there are some bugs with C++/WinRT's detection
of static lib dependencies. You might be able to get your build working with
Visual Studio on earlier versions, but not straight from MsBuild.

Also, if you're going to be running your tests in a CI build of some sort, make
sure that your tests are running on a machine running at least Windows 18362. If
your CI isn't running that version, then this doesn't matter at all.

Furthermore, you may need an updated TAEF package as well. Our CI uses the TAEF
VsTest adapter to allow ADO to run TAEF tests in CI. However, there's a bug in
the tests adapter that prevents it from running tests in a UAP context. The
`10.38.190605002` TAEF is the most recent release at the time of writing,
however, that doesn't have the fix necessary. Fortunately, the TAEF team was
kind enough to prototype a fix for us, which is the version
`10.38.190610001-uapadmin`, which we're using in this repo until an official
release with the fix is available.

## Move the C++/WinRT implementation to a static lib

By default, most (newly authored) C++/WinRT components are authored as a dll
that can be used to activate your types. However, you might have other classes
in that binary that you want to be able to test, which aren't winrt types. If
the implementation is sitting in a DLL, it'll be hard to write a TAEF unittest
dll that can call the pure c++ types you've defined.

The first thing you're going to need to do is move the implementation of your
winrt component from a dll to a static lib. Once you have the static lib, we'll
be able to link it into the dll you were previously producing, as well as being
able to link it into the dll we'll be using to test the types. Once this is
complete, your dll project will exist as little more than some extra packaging
for your new lib, as all your code will be built by the lib.

To aid in this description, I'll be referring to the projects that we changed.
The dll project we changed to a lib was the `TerminalApp` project. From it, we
created a new `TerminalAppLib` project, and changed `TerminalApp` to create a
dll by linking the lib `TerminalAppLib` produced.

### Create the static lib project

We'll start by creating a new static lib project. The easiest way to do this is
by copying your existing dll `vcxproj` file into a new file. Make sure to change
the `ProjectGuid` and to add the new project to your `.sln` file. Then, change
the `ConfigurationType` to `StaticLibrary`. This Lib should be responsible for
building all of your headers, `.cpp` files, `.idl`s for your winrt types, and
any `.xaml` files you might have.

You'll likely need to place this new file into a separate directory from the
existing dll project, as C++/WinRT uses the project directory as the root of the
intermediate build tree. Each directory should only have one `.vcxproj` file in
it. For the Terminal project, we created a subdirectory `lib/` underneath
`TerminalApp/`, and updated the `Include` paths to properly point at the
original files. You could alternatively put all the source in one directory, and
have separate `dll/` and `lib/` subdirectories from the source that are solely
responsible for building their binary.

At this point, you might face some difficulty including the right winmd
references, especially from other C++/WinRT dependencies for this project that
exist in your solution. I don't know why, but I had a fair amount of difficulty
using a `ProjectReference` from a C++/WinRT StaticLibrary to another C++/WinRT
project in my solution. If you're referring to any other projects, you'll need
to set up a reference to their built `.winmd`'s manually.

As an example, here's how we've added a reference to the `TerminalSettings`
project from our `TerminalAppLib` project:

```xml
  <ItemGroup>
    <!-- Manually add references to each of our dependent winmds. Mark them as
    private=false and CopyLocalSatelliteAssemblies=false, so that we don't
    propagate them upwards (which can make referencing this project result in
    duplicate type definitions)-->

    <Reference Include="Microsoft.Terminal.Settings">
      <HintPath>$(SolutionDir)$(Platform)\$(Configuration)\TerminalSettings\Microsoft.Terminal.Settings.winmd</HintPath>
      <IsWinMDFile>true</IsWinMDFile>
      <Private>false</Private>
      <CopyLocalSatelliteAssemblies>false</CopyLocalSatelliteAssemblies>
    </Reference>
  </ItemGroup>
```

The `HintPath` may be different depending on your project structure - verify
locally the right path to the `.winmd` file you're looking for.

Notably, you'll also need to put a `pch.h` and `pch.cpp` in the new lib's
directory, and use them instead of the `pch.h` used by the dll. C++/WinRT will be
very angry with you if you try to use a `pch.h` in another directory. Since
we're putting all the code into the static lib project, take your existing
`pch.h` and move it to the lib project's directory and create an empty `pch.h`
in the dll project's directory.

### Update the dll project

Now that we have a lib that builds all your code, we can go ahead and tear out
most of the dead code from the old dll project. Remove all the source files from
the dll's `.vcxproj` file, save for the `pch.h` and `pch.cpp` files. You _may_
need to leave the headers for any C++/WinRT types you've authored in this project
- I'm not totally sure it's necessary.

Now, to link the static lib we've created. For whatever reason, adding a
`ProjectReference` to the static lib doesn't work. So, we'll need to manually
link the lib from the lib project. You can do that by adding the lib's output
dir to your `AdditionalLibraryDirectories`, and adding the lib to your
`AdditionalDependencies`, like so:

```xml
  <ItemDefinitionGroup>
    <Link>
      <!-- Manually link with the TerminalAppLib.lib we've built. -->
      <AdditionalLibraryDirectories>$(SolutionDir)\$(Platform)\$(Configuration)\TerminalAppLib;%(AdditionalLibraryDirectories)</AdditionalLibraryDirectories>

      <AdditionalDependencies>TerminalAppLib.lib;%(AdditionalDependencies)</AdditionalDependencies>
    </Link>
  </ItemDefinitionGroup>
```

We are NOT adding a reference to the static lib project's .winmd here. As of the
2.0.190605.7 CppWinRT nuget package, this is enough for MsBuild and Visual
Studio to be able to determine that the static lib's  `.winmd` should be included
in this package.

At this point, you might have some mdmerge errors, which complain about
duplicate types in one of your dependencies. This might especially happen if one
of your dependencies (ex `A.dll`) is also a dependency for one of your _other_
dependencies (ex `B.dll`). In this example, your final output project `C.dll`
depends on both `A.dll` and `B.dll`, and `B.dll` _also_ depends on `A.dll`. If
you're seeing this, I recommend adding `Private=false` and
`CopyLocalSatelliteAssemblies=false` to your dependent dlls. In this example,
add similar code to `B.dll`:

```xml
    <ProjectReference Include="$(SolutionDir)src\cascadia\TerminalSettings\TerminalSettings.vcxproj">
      <Private>false</Private>
      <CopyLocalSatelliteAssemblies>false</CopyLocalSatelliteAssemblies>
    </ProjectReference>
```

where `TerminalSettings` is your `A.dll`, which is included by both `B` and `C`.

We additionally had an `.exe` project that was including our `TerminalApp`
project, and all its `.xbf` and `.pri` files. If you have a similar project
aggregating all your resources, you might need to update the paths to point to
the new static lib project.

At this point, you should be able to rebuild your solution, and everything
should be working just the same as before.


## Add TAEF Tests

Now that you have a static library project, you can start building your unittest
dll. Start by creating a new directory for your unittest code, and creating a
`.vcxproj` for a TAEF unittest dll. For the Terminal solution, we use the TAEF
nuget package `Taef.Redist.Wlk`.

### Referencing your C++/WinRT static lib

This step is the easiest. Add a `ProjectReference` to your static lib project,
and your lib will be linked into your unittest dll.

```xml
    <ProjectReference Include="$(SolutionDir)\src\cascadia\TerminalApp\lib\TerminalAppLib.vcxproj" />
```

Congratulations, you can now instantiate the pure c++ types you've authored in
your static lib. But what if you want to test your C++/WinRT types too?

### Using your C++/WinRT types

To be able to instantiate your C++/WinRT types in a TAEF unittest, you'll need
to rely on a new feature to Windows in version 1903 which enables unpackaged
activation of WinRT types. To do this, we'll need to author a SxS manifest that
lists each of our types, and include it in the dll, and also activate it
manually from TAEF.

#### Creating the manifest

First, you need to create a manifest file that lists each dll your test depends
upon, and each of the types in that dll. For example, here's an excerpt from the
Terminal's manifest:

```xml
<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
  <file name="TerminalSettings.dll" hashalg="SHA1">
    <activatableClass name="Microsoft.Terminal.Settings.KeyChord" threadingModel="both" xmlns="urn:schemas-microsoft-com:winrt.v1"></activatableClass>
    <activatableClass name="Microsoft.Terminal.Settings.TerminalSettings" threadingModel="both" xmlns="urn:schemas-microsoft-com:winrt.v1"></activatableClass>
  </file>
  <file name="TerminalApp.dll" hashalg="SHA1">
    <activatableClass name="TerminalApp.App" threadingModel="both" xmlns="urn:schemas-microsoft-com:winrt.v1"></activatableClass>
    <activatableClass name="TerminalApp.AppKeyBindings" threadingModel="both" xmlns="urn:schemas-microsoft-com:winrt.v1"></activatableClass>
    <activatableClass name="TerminalApp.XamlmetaDataProvider" threadingModel="both" xmlns="urn:schemas-microsoft-com:winrt.v1"></activatableClass>
  </file>
</assembly>
```

Here we have two dlls that we depend upon, `TerminalSettings.dll` and
`TerminalApp.dll`. `TerminalSettings` implements two types,
`Microsoft.Terminal.Settings.KeyChord` and
`Microsoft.Terminal.Settings.TerminalSettings`.

#### Linking the manifest to the test dll

Now that we have a manifest file, we need to embed it in your unittest dll. This
is done with the following properties in your `vcxproj` file:

```xml
  <PropertyGroup>
    <GenerateManifest>true</GenerateManifest>
    <EmbedManifest>true</EmbedManifest>
  </PropertyGroup>
  <ItemGroup>
    <Manifest Include="TerminalApp.Unit.Tests.manifest" />
  </ItemGroup>
```
where `TerminalApp.Unit.Tests.manifest` is the name of your manifest file.

Additionally, you'll need to binplace the manifest _adjacent to your test
binary_, so TAEF can find it at runtime. I've done this in the following way,
though I'm sure there's a better way:

```xml
  <ItemDefinitionGroup>
    <PostBuildEvent>
      <!-- Manually copy the manifest to our outdir, because the test will need
      to find it adjacent to us. -->
      <Command>
        (xcopy /Y &quot;$(OpenConsoleDir)src\cascadia\ut_app\TerminalApp.Unit.Tests.manifest&quot; &quot;$(OutDir)\TerminalApp.Unit.Tests.manifest*&quot; )
      </Command>
    </PostBuildEvent>
  </ItemDefinitionGroup>
```

#### Copying your dependencies

Additionally, any dlls that implement any types your test is dependent upon will
also need to be in the output directory for the test. Manually copy those DLLs
to the tests' output directory too. The updated `PostBuildEvent` looks like
this:

```xml
  <ItemDefinitionGroup>
    <PostBuildEvent>
      <Command>
        echo OutDir=$(OutDir)
        (xcopy /Y &quot;$(SolutionDir)src\cascadia\ut_app\TerminalApp.Unit.Tests.manifest&quot; &quot;$(OutDir)\TerminalApp.Unit.Tests.manifest*&quot; )

        (xcopy /Y &quot;$(SolutionDir)$(Platform)\$(Configuration)\TerminalConnection\TerminalConnection.dll&quot; &quot;$(OutDir)\TerminalConnection.dll*&quot; )
        (xcopy /Y &quot;$(SolutionDir)$(Platform)\$(Configuration)\TerminalSettings\TerminalSettings.dll&quot; &quot;$(OutDir)\TerminalSettings.dll*&quot; )
        (xcopy /Y &quot;$(SolutionDir)$(Platform)\$(Configuration)\TerminalControl\TerminalControl.dll&quot; &quot;$(OutDir)\TerminalControl.dll*&quot; )
      </Command>
    </PostBuildEvent>
  </ItemDefinitionGroup>
```

Again, verify the correct paths to your dependant C++/WinRT dlls, as they may be
different than the above

#### Activating the manifest from TAEF

Now that the manifest lives adjacent to your test dll, and all your dependent
dlls are also adjacent to the unittest dll, there's only one thing left to do.
TAEF will not use your dll's manifest by default, so you'll need to add a
property to your test class/method to tell TAEF to do so. You can do this with
the following:

```c++
class SettingsTests
{
    // Use a custom manifest to ensure that we can activate winrt types from
    // our test. This property will tell taef to manually use this as the
    // sxs manifest during this test class. It includes all the C++/WinRT
    // types we've defined, so if your test is crashing for an unknown
    // reason, make sure it's included in that file.
    BEGIN_TEST_CLASS(SettingsTests)
        TEST_CLASS_PROPERTY(L"ActivationContext", L"TerminalApp.Unit.Tests.manifest")
    END_TEST_CLASS()

    // Other Test code here
}
```

Now, if you try to add any test methods that instantiate WinRT types you've
authored, they'll work. That is of course, so long as they don't use XAML. If
you want to use any XAML types, then you'll have to keep reading.

### Using Xaml Types (with XAML Islands)

To be able to instantiate XAML types in your unittest, we'll need to make use of
the [XAML Hosting
API](https://docs.microsoft.com/en-us/windows/apps/desktop/modernize/using-the-xaml-hosting-api)
(Xaml Islands). This enables you to use XAML APIs from a Win32 context.


#### Adding XAML Hosting code

First and foremost, you'll need to add the following to your test's `precomp.h`:

```c++
#include <winrt/Windows.system.h>
#include <winrt/Windows.Foundation.Collections.h>
#include <winrt/Windows.UI.Xaml.Hosting.h>
#include <windows.ui.xaml.hosting.desktopwindowxamlsource.h>
```

If you hit a compile warning that refers to `GetCurrentTime`, you'll probably
also need the following, after you've `#include`'d `Windows.h`:

```c++
#ifdef GetCurrentTime
#undef GetCurrentTime
#endif
```

Then, somewhere in your test code, you'll need to start up Xaml Islands. I've done this in my `TEST_CLASS_SETUP`, so that I only create it once, and re-use it for each method.

```c++

class TabTests
{
    TEST_CLASS_SETUP(ClassSetup)
    {
        winrt::init_apartment(winrt::apartment_type::single_threaded);
        // Initialize the Xaml Hosting Manager
        _manager = winrt::Windows::UI::Xaml::Hosting::WindowsXamlManager::InitializeForCurrentThread();
        _source = winrt::Windows::UI::Xaml::Hosting::DesktopWindowXamlSource{};

        return true;
    }

private:
    winrt::Windows::UI::Xaml::Hosting::WindowsXamlManager _manager{ nullptr };
    winrt::Windows::UI::Xaml::Hosting::DesktopWindowXamlSource _source{ nullptr };
```

#### Authoring your test's `AppxManifest.xml`

This alone however is not enough to get XAML Islands to work. There was a fairly
substantial change to the XAML Hosting API around Windows build 18295, so it
explicitly requires that you have your executable's manifest set
`maxversiontested` to higher than that version. However, because TAEF's `te.exe`
is not so manifested, we can't just use our SxS manifest from before to set that
version. Instead, you'll need to make TAEF run your test binary in a packaged
content, with our own appxmanifest.

To do this, we'll need to author an `Appxmanifest.xml` to use with the test, and
associate that manifest with the test.

Here's the AppxManifest we're using:

```xml
<?xml version="1.0" encoding="utf-8"?>
<Package xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities" xmlns="http://schemas.microsoft.com/appx/manifest/foundation/windows10" xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10" IgnorableNamespaces="uap">

  <Identity Name="TerminalApp.Unit.Tests.Package"
          ProcessorArchitecture="neutral"
          Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US"
          Version="1.0.0.0"
          ResourceId="en-us" />
  <Properties>
    <DisplayName>TerminalApp.Unit.Tests.Package Host Process</DisplayName>
    <PublisherDisplayName>Microsoft Corp.</PublisherDisplayName>
    <Logo>taef.png</Logo>
    <Description>TAEF Packaged Cwa FullTrust Application Host Process</Description>
  </Properties>

  <Dependencies>
    <TargetDeviceFamily Name="Windows.Universal" MinVersion="10.0.18362.0" MaxVersionTested="10.0.18362.0" />
    <PackageDependency Name="Microsoft.VCLibs.140.00.Debug" MinVersion="14.0.27023.1" Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US" />
    <PackageDependency Name="Microsoft.VCLibs.140.00.Debug.UWPDesktop" MinVersion="14.0.27027.1" Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US" />
  </Dependencies>

  <Resources>
    <Resource Language="en-us" />
  </Resources>

  <Applications>
    <Application Id="TE.ProcessHost" Executable="TE.ProcessHost.exe" EntryPoint="Windows.FullTrustApplication">
      <uap:VisualElements DisplayName="TAEF Packaged Cwa FullTrust Application Host Process" Square150x150Logo="taef.png" Square44x44Logo="taef.png" Description="TAEF Packaged Cwa Application Host Process" BackgroundColor="#222222">
        <uap:SplashScreen Image="taef.png" />
      </uap:VisualElements>
    </Application>
  </Applications>

  <Capabilities>
    <rescap:Capability Name="runFullTrust"/>
  </Capabilities>

  <Extensions>
    <Extension Category="windows.activatableClass.inProcessServer">
      <InProcessServer>
        <Path>TerminalSettings.dll</Path>
        <ActivatableClass ActivatableClassId="Microsoft.Terminal.Settings.TerminalSettings" ThreadingModel="both" />
        <ActivatableClass ActivatableClassId="Microsoft.Terminal.Settings.KeyChord" ThreadingModel="both" />
      </InProcessServer>
    </Extension>
    <!-- More extensions here -->
  </Extensions>
</Package>
```

Change the `Identity.Name` and `Properties.DisplayName` to be more appropriate
for your test, as well as other properties if you feel the need. TAEF will
deploy the test package and remove it from your machine during testing, so it
doesn't terribly matter what these values are.

MAKE SURE that `MaxVersionTested` is higher than `10.0.18295.0`. If it isn't,
XAML islands will still prevent you from activating it.

UNDER NO CIRCUMSTANCE should you change the `<Application Id="TE.ProcessHost"
Executable="TE.ProcessHost.exe" EntryPoint="Windows.FullTrustApplication">`
line. This is how TAEF activates the TAEF host for your test binary. You might
get a warning about `TE.ProcessHost.exe` being deprecated in favor of
`TE.ProcessHost.UAP.exe`, but I haven't had success with the UAP version.

Lower in the file, you'll see the `Extensions` block. In here you'll put each of
the winrt dependencies that your test needs, much like we did for the previous
manifest. Note that the syntax is _not_ exactly the same as the SxS manifest.

#### Copy the AppxManifest to your `$(OutDir)`

Again, we'll need to copy this appxmanifest adjacent to the test binary so we
can load it from the test. We'll do this similar to how we did the SxS manifest
before. The complete `PostBuildEvent` now looks like this:

```xml
  <ItemDefinitionGroup>
    <PostBuildEvent>
      <Command>
        (xcopy /Y &quot;$(SolutionDir)src\cascadia\ut_app\TerminalApp.Unit.Tests.manifest&quot; &quot;$(OutDir)\TerminalApp.Unit.Tests.manifest*&quot; )

        (xcopy /Y &quot;$(SolutionDir)src\cascadia\ut_app\TerminalApp.Unit.Tests.AppxManifest.xml&quot; &quot;$(OutDir)\TerminalApp.Unit.Tests.AppxManifest.xml*&quot; )

        (xcopy /Y &quot;$(SolutionDir)$(Platform)\$(Configuration)\TerminalConnection\TerminalConnection.dll&quot; &quot;$(OutDir)\TerminalConnection.dll*&quot; )
        (xcopy /Y &quot;$(SolutionDir)$(Platform)\$(Configuration)\TerminalSettings\TerminalSettings.dll&quot; &quot;$(OutDir)\TerminalSettings.dll*&quot; )
        (xcopy /Y &quot;$(SolutionDir)$(Platform)\$(Configuration)\TerminalControl\TerminalControl.dll&quot; &quot;$(OutDir)\TerminalControl.dll*&quot; )
      </Command>
    </PostBuildEvent>
  </ItemDefinitionGroup>
```

The new line here is the line referencing
`TerminalApp.Unit.Tests.AppxManifest.xml`. You can only have one
`PostBuildEvent` per project, so don't go re-defining it for each additional
step - MsBuild will only use the last one. Again, this is probably not the best
way of copying these files over, but it works.

#### Use the AppxManifest in the test code

Now that we have the AppxManifest being binplaced next to our test, we can
finally reference it in the test. Instead of using the `ActivationContext` from
before, we'll use two new properties to tell TAEF to run this test as a package,
and to use our manifest as the AppxManifest for the package.

```c++
    BEGIN_TEST_CLASS(TabTests)
        TEST_CLASS_PROPERTY(L"RunAs", L"UAP")
        TEST_CLASS_PROPERTY(L"UAP:AppXManifest", L"TerminalApp.Unit.Tests.AppxManifest.xml")
    END_TEST_CLASS()
```

The complete Xaml Hosting test now looks like this:

```c++
    class TabTests
    {
        BEGIN_TEST_CLASS(TabTests)
            TEST_CLASS_PROPERTY(L"RunAs", L"UAP")
            TEST_CLASS_PROPERTY(L"UAP:AppXManifest", L"TerminalApp.Unit.Tests.AppxManifest.xml")
        END_TEST_CLASS()

        TEST_METHOD(TryCreateXamlObjects);

        TEST_CLASS_SETUP(ClassSetup)
        {
            winrt::init_apartment(winrt::apartment_type::single_threaded);
            // Initialize the Xaml Hosting Manager
            _manager = winrt::Windows::UI::Xaml::Hosting::WindowsXamlManager::InitializeForCurrentThread();
            _source = winrt::Windows::UI::Xaml::Hosting::DesktopWindowXamlSource{};

            return true;
        }

    private:
        winrt::Windows::UI::Xaml::Hosting::WindowsXamlManager _manager{ nullptr };
        winrt::Windows::UI::Xaml::Hosting::DesktopWindowXamlSource _source{ nullptr };
    };
    void TabTests::TryCreateXamlObjects(){ ... }
```

Congratulations, you can now use XAML types from your unittest.

### Using types from `Microsoft.UI.Xaml`

Let's say you're extra crazy and you're using the `Microsoft.UI.Xaml` nuget
package. If you've followed all the steps above exactly, you're probably already
fine! You've already put the types in your appxmanifest (there are a lot of
them). You should be able to call the `Microsoft.UI.Xaml` types without any
problems.

This is because of a few key lines we already put in the appxmanifest:

```xml
  <Dependencies>
    <TargetDeviceFamily Name="Windows.Universal" MinVersion="10.0.18362.0" MaxVersionTested="10.0.18362.0" />
    <PackageDependency Name="Microsoft.VCLibs.140.00.Debug" MinVersion="14.0.27023.1" Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US" />
    <PackageDependency Name="Microsoft.VCLibs.140.00.Debug.UWPDesktop" MinVersion="14.0.27027.1" Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US" />
  </Dependencies>
```

Without these `PackageDependency` entries for the VCLibs, Microsoft.UI.Xaml.dll
will not be able to load.
