As a rule, when develop new product in company, multiple products that have similar function are developed simultaneously. These products are subjected to a group of tests covering quality, safety and durability. If the schedule of tests is changed, the expected net presented value(NPV) of new products is changed. The tests should be scheduled with the goal of maximizing the expected NPV of the new products. A model incorporated resource constraints with the sequencing of testing tasks of multiple products is proposed in this paper. Examples show that the proposed model can handle stochastic task duration data represented by scenarios with probabilities.