Is there any way to assert the right behavior of the method?

I have a method that i need to test all of its branches. I can't find a way to assert the or verify the test is correct because both branches have almost the same behavior. btw - I can't change the given code

I have tried verifying End and Write are called but they are being called in both scenarios.

if (m_FailedOnInitialize)

{

    if (!ctx.Request.IsLocal)

    {

        ctx.Response.Write("Failed on initialization");

        ctx.Response.End();


    }

 else

    {      

            ctx.Response.Write(m_FirstError.ToString());
      ctx.Response.End();
    }
 }

*m_FailedOnInitialize Is Static field, i set it to be "true" ctx.Request.IsLocal is set to be true\false in each test

To assert the behavior i use Typemock's verification Isolate.Verify.WasCalled(() => ctx.Response.write("")); Isolate.Verify.WasNotCalled(() => ctx.Response.End());