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How to change behavior of a non-public method with an [out] parameter?
asked by (2.1k points)

1 Answer

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Isolator still doesn't have a specific API for doing this. So, in order to change the behavior of a non-public method with an out parameter, we will use the DoInstead method of Isolator.

DoInstead lets us write an alternative implementation for the faked method.
Inside the DoInstead block, we will use the context object to get access to the parameters passed to the method.

These parameters are indexed in ctx.parameters[] array, arranged by their order in the method's signature (LTR).

In this example, we fake the private func GetBools.
To get the out bool[] bools argument inside the DoInstead block, we use ctx.Parameters[0].



public class Boo
    {
        private bool[] boolsDM;

        private void GetBools(out bool[] bools)
        {
            bools = new bool[10];
        }
        
    }

public void TestOutParams()
{
      Boo b = new Boo();
            
      Isolate.NonPublic.WhenCalled(b, "GetBools").DoInstead(ctx => 
     {
          // Here we replace the out parameter to a controlled array
          // When the method gets called, it will be faked and will return the controlled array
          ctx.Parameters[0] = new bool[100];  
      });

      b.GetBoolsWraper();
      bool[] testArray = b.GetBoolsDM();

      Assert.AreEqual(100, testArray.Length);
}
answered by (4k points)
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