UnitTest.TestBuilder.FakeItEasy

Introduction

This is a concrete implementation of a test builder for FakeItEasy based on UnitTest.TestBuilder.Core

Please visit the repository to see implementations for other test frameworks.

Description

This is a test library that helps to write unit tests faster by abstractin out the boilerplate codes and let the developers focus on the actual logics of the unit tests instead.

How to use

1. Create a Builder class that inherits from FakeItEasyBuilder abstract classes

public class TestClass
{
  private class Builder : FakeItEasyBuilder<TestObject>
  {
  }
}

2. Define class properties in the Builder class.

All reference type properties including string will be dynamically created and assigned by FakeItEasyBuilder.

The TestObject is created using its public constructor that has the most parameters. If the parameter is the same type as any of the properties defined in the Builder, the property of the Builder will be passed in as the parameter to the constructor. Hence, the TestObject will have reference to the properties defined in the Builder.

public class TestClass
{
  private class Builder : FakeItEasyBuilder<TestObject>
  {
       Fake<IServiceA> ServiceA {get; private set;}
  }
}

3. You can optionally override the creation of the property objects in the constructor of the Builder class

  private class Builder : FakeItEasyBuilder<TestObject>
  {
      public IServiceA ServiceA {get; private set;}
      
      public Builder(IContainer container)
      {
         // override the creation of ServiceA
         ServiceA = new ServiceA();
      }
  }

4. You can optionally use dependency injection for the creation of the properties. You can define a custom DI container using your favorite DI library that implements the IContainer interface.

5. You can optionally override the creation of the TestObject by overriding the CreateObject method.

  private class Builder : FakeItEasyBuilder<TestObject>
  {
      public IServiceA ServiceA {get; private set;}
      
      /// You can pass in additional parameters to create your custom TestObject
      /// through the *args* paramater
      protected override TestObject CreateObject(params object[] args)
      {
        return new TestObject();
      }
  }

Examples

Check out the Examples in Unit Tests project for more details

    public interface IRateService
    {
        double GetRate();
    }

    public class RateCalculator
    {
        private readonly IRateService _rateService;

        public RateCalculator(IRateService rateService)
        {
            _rateService = rateService;
        }

        public double GetTodayRate()
        {
            return 2 * _rateService.GetRate();
        }

        public double GetTomorrowRate()
        {
            return 3 * _rateService.GetRate();
        }
    }

    [TestClass]
    public class ExampleTests
    {
        private class Builder : FakeItEasyBuilder<RateCalculator>
        {
            // This property will be auto-populated by the base builder
            public Fake<IRateService> RateService { get; private set; }

            public Builder() : this(null) { }

            public Builder(IContainer container) : base(container) { }
        }

        [Fact]
        public void GetTodayRate_WithRate_ReturnCorrectRate()
        {
            var builder = new Builder();

            //set up the getRate method to return 2
            builder.RateService.CallsTo(a => a.GetRate()).Returns(2);

            var calculator = builder.Build();

            //Act
            var result = calculator.GetTodayRate();

            //Assert
            Assert.Equal(4.0, result);

            //verify RateService.GetRate() was called
            builder.RateService.CallsTo(a => a.GetRate()).MustHaveHappened();
        }

        [Fact]
        public void GetTomorrowRate_WithRate_ReturnCorrectRate()
        {
            var builder = new Builder();

            //set up the getRate method to return 2
            builder.RateService.CallsTo(a => a.GetRate()).Returns(2);

            var calculator = builder.Build();

            //Act
            var result = calculator.GetTomorrowRate();

            //Assert
            Assert.Equal(6.0, result);

            //verify RateService.GetRate() was called
            builder.RateService.CallsTo(a => a.GetRate()).MustHaveHappened();
        }
    }

Last Updated: Jan-13-2020 (Jacky-Mo)