Learn TypeScript 3 by Building Web Applications

Testing approach and mindset

When you design and implement tests, you need to start thinking like a malicious hacker. You need to start getting suspicious about everything and to verify everything. You need to think about positive cases, edge cases, and also abnormal scenarios.

A positive case or scenario represents the base case, that is, the ideal world scenario where everything goes according to plan. Of course, that is the first thing to validate. This simply means validating that the code actually works with valid input. Ideally, you should check the full range of valid inputs (when possible).

But you shouldn't stop there. You should then look at more exceptional cases and test the edge cases (that is, the boundaries). For example, ...