How to corner dependencies that are hard to mock or extract interface.

SomeClass-bad.cs

class SomeClass{

  private BigHorrificMonsterClass myBaby = new BigHorrificMonsterClass();

  public int DoSomething( int value ){
    int cradled = myBaby.cradle( value );

    return value + cradled;
  }
}

SomeClass-good.cs

class SomeClass{

  private BigHorrificMonsterClass myBaby = new BigHorrificMonsterClass();

  public int DoSomething( int value ){
    int cradled = cradle( value );

    return value + cradled;
  }

  protected virtual int cradle( int value ){
    return myBaby.cradle( value );
  }
}

SomeClassSub.cs

class SomeClassSub : SomeClass {
  public int cradleReturnValue;

  protected virtual int cradle( int value ){
    return cradleReturnValue;
  }
}

SomeClassTests.cs

class SomeClassTest{

  [TestMethod]
  public void ItAddsValueToCradled(){
    SomeClassSub someClass = new SomeClassSub();
    someClass.cradleReturnValue = 5;

    int result = someClass.DoSomething( 8 );

    Assert.AreEqual( 13, result );
  }

}