Full Stack Radio

A podcast for developers interested in building great software products. Hosted by Adam Wathan.

144: Gary Bernhardt - TypeScript and Testing

In this episode, Adam talks to Gary Bernhardt about building Execute Program, why he chose to build it as a full-stack TypeScript application, and the implications using TypeScript has on what you need to test.

Topics include:

  • Why Gary decided to write Execute Program as a full-stack TypeScript application instead of using a Ruby or Python backend like he may have traditionally
  • Do you actually have to write less tests if you have a good type system?
  • What does a good type system give you that tests can't give you?
  • Using io-ts to type check incoming data
  • How to think about structuring your code to best take advantage of the benefits your type system gives you and minimize the need to write tests
  • Pushing conditional logic to the core of your system to reduce the number of tests you need to write at the edges
  • The correlation between type errors and behavioral bugs, and how a type system can help you catch mistakes you don't think to test for
  • Do type errors signal that you're missing a test?
  • Structural vs. nominal type systems, and the benefits of structural type systems like used by TypeScript and Go
  • Best practices for type-checking within a function in a structural type system like TypeScript
  • The power of supporting literal types like true or "active" in addition to traditional types


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