public void MakeOptional_AlreadyOptional_ReturnsExpected() { var innerReader = new ColumnIndexValueReader(1); OneToOneMap <string> propertyMap = Map(t => t.Value).WithReader(innerReader); Assert.Same(propertyMap, propertyMap.MakeOptional()); Assert.True(propertyMap.Optional); Assert.Same(propertyMap, propertyMap.MakeOptional()); Assert.True(propertyMap.Optional); Assert.Same(innerReader, propertyMap.CellReader); }