Boundary value testing involves selecting values at the edge of the input domain. For a field that accepts a year of birth between 1900 and 2004, we need to include values just inside, just outside, and at the boundaries. Thus, the values are 1899 (just outside the lower boundary), 1900 (lower boundary), 2004 (upper boundary), and 2005 (just outside the upper boundary). This ensures comprehensive testing of the field's boundary conditions.