Fake It Easy

• Donald Belcham and Jim Cooper
• Easy mocking library for .Net framework
  • A framework for creating all types of fake objects (mocks, stubs, etc..)
• Easily readable
• Package Manager Console Install-Package FakeItEasy
• https://fakeiteasy.github.io/
• Github
• Key Points of a Good Unit Test:
  • Atomic
  • Deterministic
  • Repeatable
  • Order Independent & Isolated
  • Fast
  • Easy to Setup
• Hand rolled mock objects. Creating mock classes and using them (no third party mock framework)
• Fake v/s Mock v/s Stub
  • No distinction between the three when defining the object
  • Object usage determines if it is a Fake or Mock or Stub
• Supports .Net 4.0 or higher
• No support for Sealed, Static, Private only Constructor Class, private methods
• Creating Fakes : There are several restrictions in creating Fake Objects

Examples

• Faking

A.Fake<T>();
var fake = new Fake<IFoo>();
A.CollectionOfFake<T>(10);

// Create wrapper - unconfigured calls will be forwarded to wrapped
var wrapped = new FooClass("foo", "bar");
var foo = A.Fake<IFoo>(x => x.Wrapping(wrapped));

• AAA
  • Arrange
    • Creating a fake object
    • Pass the fake to SUT (System Under Test)
  • Act
    • Execute the SUT
  • Assert
    • Verify SUT's interaction with the fake object
  • Code Example

  //Arrange
  var fakeRepository = A.Fake<ICustomerRepository>();
  var service = new CustomerService(fakeRepository);
  
  //Act
  service.Create(new CustomerDto());
  
  //Assert
  A.CallTo(
        () => fakerepository.Save<>(A<Customer>.Ignored))    //Interesting
        .MustHaveHappened();
  

• Method Call Count Examples

MustHaveHappened(Repeated.Atleast.Once)
MustHaveHappened(Repeated.Exactly.Twice)
MustHaveHappened(Repeated.Exactly.Times(6))
MustHaveHappened(Repeated.NoMoreThan.Once)
MustHaveHappened(Repeated.Never)
MustNotHaveHappened()

• When there is no need of assertion inside a Test Method?
  • When an [ExpectedException] attribute is set above the test method
• Returns

A.CallTo(() => fakeObject.Method(A<ParamType>.Ignored)).Returns(FakeValue);

• Out & Ref Parameter

// Code
var mailingAddressSuccessfullyCreated = mailingAddressFactory.TryParse(customer.Address, out MailingAddress, out doorNo)


// Test Code
MailingAddress returnedMailingAddress;
int returnedDoorNo;
A.CallTo(
  () => fakeMailingAddressFactory.Tryparse(
    A.Fake<String>.Ignored, out returnedMailingAddress, out returnedDoorNo))
  .Returns(true)
  .AssignsOutAndRefParameters(new MailingAddress(), 1052);

• Return Different Value in a Loop

// Code
for {
  customer.Id = _idFactory.Create();
}

// Test
A.CallTo(
  () => fakeidFactory.Create())
  .ReturnsNextFromSequence(1, 2, 3, 4, 5);

• Arguments A<T>.Ignored | A<T>.That...

// Code
GetFullName(firstName, lastName)
{
  var fullName = firstName + " " + lastName;
  return fullName;
}

// Test
A.CallTo(
  () => fakeFullNameBuilder.GetFullName("S", "Kota"))
  .MustHaveHappened();

A.CallTo(
  () => fakeFullNameBuilder.GetFullName(A<string>.That.Matches(s=>s.Equals("s")), "Kota"))
  .MustHaveHappened();

• Exceptions

// Arrange
A.CallTo(
  ()=> fakeObject.fakeMethod(A<T>.Ignored))
  .Throws(new CustomException());

// Assert
//Check for Logging, re-thrown etc..

• Properties
  • Setters

  Assert.That(fakeCustomRepository.FullName, Is.Not.Empty);
  Assert.That(fakeCustomRepository.FullName, Is.Not.Null);
  

  • Getters

  A.CallTo(() => fakeID.Age)MustHaveHappened();
  

  • Auto Mocking Hierarchies

  // Code
  var workStationId = _applicationSettings.SystemConfiguration.AuditingInformation.WorkStationId;
  
  // Test
  // Arrange
  A.CallTo(() => 
         fakeApplicationSettings
         .SystemConfiguration
         .AuditingInformation
         .WorkStationId)
   .Returns(5);
  // Assert
  A.CallTo(() => 
         fakeApplicationSettings
         .SystemConfiguration
         .AuditingInformation
         .WorkStationId)
   .MustHaveHappened();
  

• Events

//Code
_customerRepository.NotifySalesTeam += NotifySalesTeam;
NotifySalesTeam(sender, NotifySalesTeamEventArgs e);

//Test
// Act
fakeCustomerRepository.NotifySalesTeam +=
  Raise.With(new NotifySalesTeamEventArgs())
    .Now;

• Ordered Assertions

fake.CreateScope();
scope.OrderedAssertions();

Advanced Faking

• Strict & Loose Mocking
  • Strict: Raises exception for anything on a mock object that doesn't have an explicitly declared expectation
  • Loose: No exception raised. Returns Default Values when no exception is explicitly declared.
  • Fake It Easy will not create Strict Objects
• Protected Members. MethodName is hardcoded in string format

  A.CallTo(fakeRepository)    //returns fakeObject
    .Where(x => x.Method.Name == "ProtectedMethodName")    //reference of protected method returned.
  

• No Intellisense