Tmds.ExecFunction

Tmds.ExecFunction is a library that makes it simple to execute a function in a separate process. This can be interesting for writing tests that require a separate process, or running some code with a different lifetime as the .NET application process. The library is based on the corefx RemoteExecutorTestBase class.

Supported platforms

This library supports .NET Core 2.0+ on Windows, Linux, and macOS.

Usage

The main method of the library is ExecFunction.Run. It accepts a delegate that is the function to execute in the remote process. The function can have the same signature of a .NET Main: a void/string[] argument, and a void/int/Task/Task<int> return type.

For example:

ExecFunction.Run(() => Console.WriteLine("Hello from child process!"));

The ProcessStartInfo that is used to start the process can be configured, by adding a configuration delegate:

ExecFunction.Run(..., o => o.StartInfo.RedirectStandardOutput = true);

If you want to re-use the same configuration for multiple invocations you can use the FunctionExecutor class.

private FunctionExecutor FunctionExecutor = new FunctionExecutor(o.StartInfo.RedirectStandardOutput = true);

// Now call FunctionExecutor.Run(...).

The configuration allows you to add an OnExit action. For example, you can use this FunctionExecutor in an xunit project and Assert in the child process:

private FunctionExecutor FunctionExecutor = new FunctionExecutor(
    o =>
    {
        o.StartInfo.RedirectStandardError = true;
        o.OnExit = p =>
        {
            if (p.ExitCode != 0)
            {
                string message = $"Function exit code failed with exit code: {p.ExitCode}" + Environment.NewLine +
                                  p.StandardError.ReadToEnd();
                throw new Xunit.Sdk.XunitException(message);
            }
        };
    }
);

[Fact]
public void Test()
{
    FunctionExecutor.Run(
        (string[] args) => 
        {
            Assert.Equal("arg1", args[0]);
            Assert.Equal("arg2", args[1]);
        },
        new string[] { "arg1", "arg2" }
    );
}

When ExecFunction is used from the dotnet host, it will work out-of-the box. To make ExecFunction work from an application host (that is, when you've published your application as a native binary), you need to add a hook in the main function:

static int Main(string[] args)
{
    if (ExecFunction.IsExecFunctionCommand(args))
    {
        return ExecFunction.Program.Main(args);
    }
    else
    {
        ExecFunction.Run(() => System.Console.WriteLine("Hello world!"));
        return 0;
    }
}

NuGet feed

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <add key="tmds" value="https://www.myget.org/F/tmds/api/v3/index.json" />
  </packageSources>
</configuration>