2.15. Risks and Contingencies
I sometimes use the title "Open Issues" for this section. In it, I address potential or likely events that could make the test plan difficult or impossible to carry out. Topics might include training needs, the availability of additional development support for debugging if an exceptional number of bugs are found, and so forth. Alternatively, you can include this type of information when you discuss continuation criteria.
Strictly speaking, most advocates of good development processes encourage a global approach to risk management. If you work on a project in which the entire team has a single risk-management plan, you might be able to omit this section by including these concerns in that plan.
 See, for example, McConnell's Software Project Survival Guide.