Don't make weak tests to create a false sensation of coverage.

TL;DR: Test Assertions should be precise. Not too Vague and not too specific. There is no silver bullet.

Problems

• False Negatives

• Lack of Trust

Solutions

1. Check the right case

2. Assert for a functional case.

3. Don't test implementation.

Sample Code

Wrong

square = Square(5)

assert square.area() != 0

# This will lead to false negatives since it is too vague

Right

square = Square(5)

assert square.area() = 25

# Assertion should be precise

Detection

With Mutation Testing techniques we can find these errors on our tests.

Tags

• Testing

Conclusion

We should use development techniques like TDD that request concrete business cases and make concrete assertions based on our domain.

Relations

More info

• Test Driven Development

• The Only Design Principle

• Mutation Testing

Credits

This smell was inspired by Mario Cervera and used with his permission.

Photo by Fleur on Unsplash

A program that produces incorrect results twice as fast is infinitely slower.

John Osterhout

This article is part of the CodeSmell Series.