When
Applied, the When clause enables the arrangement only if certain conditions are satisfied. It specifies what must be true (along with any argument matcher, or IgnoreInstance() or IgnoreArguments() clauses used on the arrangement) for that arrangement to be executed and its expectations updated. To understand how to use the When method, check the next examples:
How It Works
Let's assume we have the following interface:
public interface IFoo
{
bool IsCalled();
string Prop { get; set; }
}
Public Interface IFoo
Function IsCalled() As Boolean
Property Prop() As String
End Interface
Using JustMock, we can set a certain arrangement to be used only if another expectations are met. The below test method is a demonstration of this. The IsCalled function is arranged to return true only if Prop is equal to "test".
[TestMethod]
public void IsCalled_ShouldReturnTrue_WithMockedDependencies()
{
// Arrange
var foo = Mock.Create<IFoo>();
Mock.Arrange(() => foo.Prop).Returns("test");
Mock.Arrange(() => foo.IsCalled()).When(() => foo.Prop == "test").Returns(true);
// Assert
Assert.IsTrue(foo.IsCalled());
}
<TestMethod> _
Public Sub IsCalled_ShouldReturnTrue_WithMockedDependencies()
' Arrange
Dim foo = Mock.Create(Of IFoo)()
Mock.Arrange(Function() foo.Prop).Returns("test")
Mock.Arrange(Function() foo.IsCalled()).When(Function() foo.Prop = "test").Returns(True)
' Assert
Assert.IsTrue(foo.IsCalled())
End Sub
How It Helps
There are situations where you need to make an arrangement that will only work when a certain condition is true. If the condition is related to that member's input arguments, you can use Matchers. However, if the condition is not related to them, you can achieve the desired behavior by using the When method.
Look at the following interface:
public interface IRequest
{
string Method { get; set; }
string GetResponse();
}
Public Interface IRequest
Property Method() As String
Function GetResponse() As String
End Interface
In the test, we will check if GetResponse() has been called once when Method == "GET" and once more when Method == "POST". Note that, the Method property is unrelated to the GetResponse() method.
[TestMethod]
public void ShouldAssertThatSUTCallsGetResponseWithBothGetAndPostMethods()
{
// Arrange
var mock = Mock.Create<IRequest>();
Mock.Arrange(() => mock.GetResponse()).When(() => mock.Method == "GET").OccursOnce();
Mock.Arrange(() => mock.GetResponse()).When(() => mock.Method == "POST").OccursOnce();
// Act
mock.Method = "GET";
mock.GetResponse();
mock.Method = "POST";
mock.GetResponse();
// Assert
Mock.Assert(mock);
}
<TestMethod> _
Public Sub ShouldAssertThatSUTCallsGetResponseWithBothGetAndPostMethods()
' Arrange
Dim requestMock = Mock.Create(Of IRequest)()
Mock.Arrange(Function() requestMock.GetResponse()).When(Function() requestMock.Method = "GET").OccursOnce()
Mock.Arrange(Function() requestMock.GetResponse()).When(Function() requestMock.Method = "POST").OccursOnce()
' Act
requestMock.Method = "GET"
requestMock.GetResponse()
requestMock.Method = "POST"
requestMock.GetResponse()
' Assert
Mock.Assert(requestMock)
End Sub