Solvequill Blog · coding · 4 min read · 2 views
Think of tests as small promises
Write tests that describe behavior clearly enough to protect future changes.
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A useful test is a promise about behavior. It should fail when that promise is broken and stay quiet when implementation details change.
The main idea
Start with one normal case, one edge case, and one failure case. Name each test in plain language.
A short example
For a discount function, test a regular price, a zero discount, and an invalid negative price.
1expect(applyDiscount(100, 0.2)).toBe(80);2expect(applyDiscount(100, 0)).toBe(100);3expect(() => applyDiscount(-5, 0.2)).toThrow();Check while you solve
- Test behavior, not private implementation.
- Use examples a human can read.
- Add a regression test when you fix a bug.
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