What are some arguments against user experience testing?
With some pieces of design, there is enough common knowledge (of both good and bad practices) that you don't have to test to see if they work (or don't). There's a pretty substantial body of literature now, so fixing minor usability or ergonomic issues by an experienced designer shouldn't require testing to know if it will be successful or not.
What does require testing:
- new products
- products in a new context/market
- products with a new audience
- products that span across diverse cultures/user groups
- novel pieces of functionality
- fixed products where you need to know the metrics of how much it has improved after a redesign
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