Environment
| Product | Version |
|---|---|
| Progress® Telerik® JustMock | 2023.3.1011.155 |
Description
While attempting to mock a method that has a ByRef argument, the expectation is to have the ByRef argument receive a predefined value upon method execution. However, achieving this behavior might not be straightforward. This KB article demonstrates how to correctly mock a method with ByRef arguments using Telerik JustMock to ensure the ByRef parameter is overwritten as expected.
Considering the following method under test:
public class SomeDemoClass
{
public void SomeByRefParameter(string value, ref string @out)
{
out = "Nonsense";
}
}
Public Class SomeDemoClass
Public Sub SomeByRefParameter(value As String, ByRef out As String)
out = "Nonsense"
End Sub
End Class
and the test:
[TestMethod]
public void ArgRefTest()
{
var classUnderTest = new SomeDemoClass();
string value = "Hello";
string expectedResult = "The value passed in parameter 'value' is 'Hello'";
string actualResult = null;
// Arrange
Mock.Arrange(() => classUnderTest.SomeByRefParameter(value, Arg.Ref(expectedResult).Value));
// Act
classUnderTest.SomeByRefParameter(value, actualResult);
// Assert
Assert.AreEqual(expectedResult, actualResult);
}
<TestMethod>
Public Sub ArgRefTest()
Dim classUnderTest = New SomeDemoClass()
Dim value = "Hello"
Dim expectedResult = "The value passed in parameter 'value' is 'Hello'"
Dim actualResult As String = Nothing
' Arrange
Mock.Arrange(Sub() classUnderTest.SomeByRefParameter(value, Arg.Ref(expectedResult).Value))
' Act
classUnderTest.SomeByRefParameter(value, actualResult)
' Assert
Assert.AreEqual(expectedResult, actualResult)
End Sub
Solution
To mock a method that includes ByRef arguments and to ensure the ByRef parameter is appropriately overwritten, follow the steps outlined below. The key is to use the DoInstead arrangement clause effectively.
Use the
Mock.Arrangemethod to set up the arrangement for the method. Utilize theArg.RefandArg.AnyStringmatchers as needed to specify the conditions under which the arrangement applies.Within the
DoInsteadclause, specify the action that overwrites the ByRef argument with the desired value.
Here is an example demonstrating how to apply these steps in a unit test with Telerik JustMock:
[TestMethod]
public void ArgRefTest()
{
var classUnderTest = new SomeDemoClass();
string value = "Hello";
string expectedResult = "The value passed in parameter 'value' is 'Hello'";
string actualResult = null;
// Arrange
Mock.Arrange(() => classUnderTest.SomeByRefParameter(value, Arg.Ref(Arg.AnyString).Value))
.DoInstead((val, ref @out) => out = expectedResult);
// Act
classUnderTest.SomeByRefParameter(value, actualResult);
// Assert
Assert.AreEqual(expectedResult, actualResult);
}
<TestMethod>
Public Sub ArgRefTest()
Dim classUnderTest = New SomeDemoClass()
Dim value = "Hello"
Dim expectedResult = "The value passed in parameter 'value' is 'Hello'"
Dim actualResult As String = Nothing
' Arrange
Mock.Arrange(Sub() classUnderTest.SomeByRefParameter(value, Arg.Ref(Arg.AnyString).Value)) _
.DoInstead(Sub(val, ByRef out) out = expectedResult)
' Act
classUnderTest.SomeByRefParameter(value, actualResult)
' Assert
Assert.AreEqual(expectedResult, actualResult)
End Sub
In this code snippet, the DoInstead clause is used to overwrite the ByRef argument out with the expectedResult variable. The Arg.Ref(Arg.AnyString).Value matcher is employed to apply the arrangement regardless of the string value passed as an argument.