Iterative usability testing
Usability testing is most effective when conducted iteratively (repeatedly) throughout the development of a product. Iterative testing means conducting several periodic tests over the course of product development. Usually, iterative testing is implemented early so the results will be of the most value to the development of the product.

It is possible to test usability on prototypes or models of the actual product rather than the actual product itself. The prototypes can range from low similarity (using a prototype of the product that does not look like the final product), medium similarity (using a product that looks but may not function like the final product), or high similarity testing (using a product that looks and functions like the final product).
Low similarity
Two examples of low similarity testing are paper prototyping and matching exercise.
- Paper prototyping displays the product on paper and ask users’ reactions to it.
- Matching exercises are used to understand the appropriateness of labels. Users are given a list of commands or labels and asked to match them to a second list of terms or icons. This technique can yield useful information such as, “Do users recognize the labels or commands as intended?”
Medium to high similarity
An example of medium to high similarity testing is using a limited number of Web pages to test an entire Web site.

