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Unit+integration-testing-dotnetcore.md

Unit testing, Integration testing & Dependency Injection with Microsoft .NET Core

We'll walk through the basics of setting up a test projects using dotnet test, and take you through including Microsoft's dependency injection framework and writing Integration test.

Project setup

You'll want to set up three projects - a class library and two test projects like so:

mkdir WeatherConverter
cd WeatherConverter

mkdir src
mkdir src/WeatherConverter

mkdir test
mkdir test/Unit
mkdir test/Integration

Then you'll need to create a global.json file in the project root as follows:

{
    "projects": [
        "src",
        "test"
    ]
}

Our class library is going to convert temperatures from Celcius to Farenheight and will also be able to look up the current temperature given a city - naturally we want to build this using TDD!

Let's start by creating some unit tests - we'll CD into the Unit test folder and use the dotnet cli to create an xunit test project:

cd test/Unit
dotnet new -t xunittest

Then build and run the tests with:

dotnet restore
dotnet test

Hopefully this should build and run the one example test - lets change this so we can start testing the Temperature class we want to write:

mv Tests.cs Temperature_AsCelciusShould.cs

Then I'll write my first test as follows:

using System;
using Xunit;

namespace Tests.Unit
{
    public class Temperature_AsCelciusShould
    {
        [Fact]
        public void Return0WhenGiven0() 
        {

            var temperature = new Temperature(0);

            decimal actual = temperature.AsCelcius();


            decimal expected = 0;
            Assert.Equal(actual, expected);
        }
    }
}

Then we'll create our Temperature class and try to get the solution building and the test passing:

src/TemperatureCalculator/Temperature.cs:
-------

using System;

namespace TemperatureCalculator
{
    public class Temperature
    {
        public Temperature (decimal temperatureCelcius){
        }
        
        public decimal AsCelcius()
        {    
            throw new NotImplementedException();
        }
    }
}

You'll also need to reference the class library project from the unit test project by adding the reference in to test/Unit/project.json

...

"dependencies": {
    "System.Runtime.Serialization.Primitives": "4.1.1",
    "xunit": "2.1.0",
    "dotnet-test-xunit": "1.0.0-rc2-192208-24",
    "TemperatureCalculator": {
      "target": "project"
    }
  },
  ...

Then you'll need to run:

dotnet restore

to resolve the dependency before running the tests. Now we can go about fixing the test and adding some more.