Running a Custom Logic

When to Use

When you want to run your logic while the constructor runs.

Syntax

C#

var handle = Isolate.Fake.NextInstance<Dependency>(Members.ReturnRecursiveFakes,
  context=>
  {
  // action here
  });

VB
Dim handle = Isolate.Fake.NextInstance(Of Dependency)(Members.ReturnRecursiveFakes, 
  Function/Sub(context)
  // action here
  End Function/Sub)

Samples

To run custom logic in a faked method, use DoInstead after WhenCalled and provide your own delegate. DoInstead passes MethodCallContext with the following members:

Member	Description
Instance	An instance of the calling object (null if the method is static)
Parameters	Array of objects of arguments passed to the method (if exist)
Method	A MethodBase object that contains the method metadata that can be used for choosing the required behavior
WillCallOriginal()	Calls the original implementation

Sample 1

C#

[TestMethod, Isolated]
public void CallConstructor_DoCustomCode()
{
  var handle = Isolate.Fake.NextInstance<Dependency>(Members.ReturnRecursiveFakes, context =>
  {
    if ((string) context.Parameters[1] == "typemock")
    {
      // contructor is faked
      return;
    }

    context.WillCallOriginal(); // constructor will be called
  });

  var classUnderTest = new ClassUnderTest();
  var dependency = classUnderTest.Create("typemock");
  var result = classUnderTest.GetString(dependency);

  Assert.AreEqual("0", result);
}

public class ClassUnderTest
{
  public string GetString(Dependency user)
  {
    return user.Name + user.Age.ToString();
  }

  public Dependency Create(string name)
  {
    return new Dependency(0, name);
  }
}

public class Dependency
{
  public int Age;
  public string Name;

  public Dependency(int age, string name)
  {
    Age = age;
    Name = name;
  }
}

VB

<TestMethod(), Isolated()>
Public Sub CallConstructor_DoCustomCode()
    Dim handle = Isolate.Fake.
        NextInstance(Of Dependency)(Members.ReturnRecursiveFakes, Sub(context)
                 If DirectCast(context.Parameters(1), String) = "typemock" Then
                     ' contructor is faked
                     Return
                 End If

                 ' constructor will be called
                 context.WillCallOriginal()

             End Sub)

    Dim classUnderTest = New ClassUnderTest()
    Dim dependency = classUnderTest.Create("typemock")
    Dim result = classUnderTest.GetString(dependency)

    Assert.AreEqual("0", result)
End Sub

Sample 2: Setting a Field from a Constructor

C#

[TestMethod,Isolated]
public void SetNewDependencyName_NameWillBeTypemockRocks()
{
    Isolate.Fake.NextInstance<Dependency>(Members.ReturnRecursiveFakes,context=> 
    {
        (context.Instance as Dependency).Name = "Typemock Rocks!!";
    });

    var result = new ClassUnderTest().Create();

    Assert.AreEqual("Typemock Rocks!!", result.Name);
}


public class ClassUnderTest
{
    private Dependency dependency;
	
    public Dependency Create()
    {
        dependency = new Dependency();
        return dependency;
    }
}

public class Dependency
{
    public string Name { get; set; } 

    public Dependency()
    {
        Name = "Typemock";
    }
}

VB

<TestMethod(), Isolated()>
Public Sub SetNewDependencyName_NameWillBeTypemockRocks()
	Isolate.Fake.NextInstance(Of Dependency)(Members.ReturnRecursiveFakes, Function(context) 
	TryCast(context.Instance, Dependency).Name = "Typemock Rocks!!"

End Function)
	Dim result = New ClassUnderTest().Create()

	Assert.AreEqual("Typemock Rocks!!", result.Name)
End Sub

Public Class ClassUnderTest
    Private dependency As Dependency

    Public Function Create() As Dependency
        dependency = New Dependency()
        Return dependency
    End Function
End Class

Public Class Dependency
    Public Property Name() As String
        Get
            Return m_Name
        End Get
        Set
            m_Name = Value
        End Set
    End Property
    Private m_Name As String

    Public Sub New()
        Name = "Typemock"
    End Sub
End Class