Discussion on: The three A’s of Unit Testing

Nice example! I seen some similar posts in which they tested the values of the actual properties instead of the output of methods, which is a very bad practice, because the internal state isn't relevant to unit testing, just the surface of contact with the external world. So:

// Doing it like in your example, which is ideal:

const instance = new Class("value");
const output = instance.method();
expect(output).toBe("expected-value");

// Bad practice I seen:

const instance = new Class("value");
expect(instance.value).toBe("value");

Thanks for sharing! Cheers!