07 · Testing: proving it works

75% coverage is the law, but coverage is not the point — assertions are. Write a test that would actually catch a bug.

Tests build their own world

Test methods see no org data. Build every record you need inside the test — it is more work and it is also why your tests still pass in a fresh sandbox.

Assert like you mean it

A test without assertions is a coverage donation. Assert the field values you changed, the errors you expected, and the records you did not touch.

Practice in your org

• Open your Developer Edition org and follow along step by step
• Change one thing at a time and note what happens
• When something breaks, read the error before searching for it