How to run setup code only once in an xUnit.net test

Question

I'm trying to setup my tests using Xunit. I have a requirement to delete all images in a folder start of the tests, and then each method does some image resizing and saves a copy of it's output to the folder. The folder should only be emptied once, and then each method will save their own image into the folder.

When I use IUseFixture<T>, the ClearVisualTestResultFolder function is still being called before every test, so I only end up with one image in the folder.

public class Fixture
{
    public void Setup()
    {
        ImageHelperTest.ClearVisualTestResultFolder();
    }
}

public class ImageHelperTest : IUseFixture<EngDev.Test.Fixture>
{
    public void SetFixture(EngDev.Test.Fixture data)
    {
        data.Setup();
    }

    public static void ClearVisualTestResultFolder()
    {
        // Logic to clear folder
    }
}

If I put the ClearVisualTestResultFolder in the constructor, it is also being called once for every test method. I need this just run once before all test methods are executed, how can I achieve this?

If it matters, I use the ReSharper test runner.

Answer 1

Following the guidance in this xUnit discussion topic, it looks like you need to implement a constructor on the Fixture and also implement IDisposable. Here's a complete sample that behaves the way you want:

using System;
using System.Diagnostics;
using Xunit;
using Xunit.Sdk;

namespace xUnitSample
{
    public class SomeFixture : IDisposable
    {
        public SomeFixture()
        {
            Console.WriteLine("SomeFixture ctor: This should only be run once");
        }

        public void SomeMethod()
        {
            Console.WriteLine("SomeFixture::SomeMethod()");
        }

        public void Dispose()
        {
            Console.WriteLine("SomeFixture: Disposing SomeFixture");
        }
    }

    public class TestSample : IUseFixture<SomeFixture>, IDisposable
    {
        public void SetFixture(SomeFixture data)
        {
            Console.WriteLine("TestSample::SetFixture(): Calling SomeMethod");
            data.SomeMethod();
        }

        public TestSample()
        {
            Console.WriteLine("This should be run once before every test " + DateTime.Now.Ticks);
        }

        [Fact]
        public void Test1()
        {
            Console.WriteLine("This is test one.");
        }

        [Fact]
        public void Test2()
        {
            Console.WriteLine("This is test two.");
        }

        public void Dispose()
        {
            Console.WriteLine("Disposing");
        }
    }
}

When running this from the console runner, you'll see the following output:

D:\xUnit>xunit.console.clr4.exe test.dll /html foo.htm xUnit.net console test runner (64-bit .NET 4.0.30319.17929) Copyright (C) 2007-11 Microsoft Corporation.

xunit.dll: Version 1.9.1.1600 Test assembly: test.dll

SomeFixture ctor: This should only be run once

Tests complete: 2 of 2

SomeFixture: Disposing SomeFixture

2 total, 0 failed, 0 skipped, took 0.686 seconds

Then, when you crack open the test output file foo.htm, you'll see the other test output.