# 11.5. Test a pen

1. Who would use the pen? Students, painters?
2. Black box or white box? Can I test components of the pen?
3. What are the use cases?
4. What are the bounds of use?
5. In what conditions should it fail, what would that mean?

Children are going to use the pen, they will be drawing on clothing. The pen is intended to wash off when cleaning the clothing. It will have colors red, green, blue and black.

1. Fact check: verify that the pen is felt tip and that the ink is one of the allowed colors
2. Intended use: pen writes properly on clothing
3. Intended use: color washes off when clothing is washed. What about cold water washing, hot water?
4. Safety: is the pen non-toxic for children?
5. Unintended uses: what if the children write on other surfaces? The pen should hold up

