Code Smell 312 - Too Many Asserts

#web3 #webdev #beginners #programming

Cluttered tests hide real problems

TL;DR: You put multiple assertions in one test, making failures hard to analyze.

Problems 😔

Readability
Fragile tests
Slow Tests
Debugging pain
Coupled logic
Maintenance nightmare
Ambiguous failures
Generic assertions

Solutions 😃

Follow the One-assert-per-test rule
Extract assert methods
Use descriptive test names
Group related checks
Refactor test logic in smaller pieces

Refactorings ⚙️

Refactoring 002 - Extract Method

Maxi Contieri ・ Nov 25 '21

#refactoring #oop #webdev #codenewbie

Refactoring 013 - Remove Repeated Code

Maxi Contieri ・ Jun 16 '24

#webdev #beginners #programming #tutorial

Refactoring 010 - Extract Method Object

Maxi Contieri ・ Nov 7 '22

#webdev #javascript #beginners #programming

Refactoring 011 - Replace Comments with Tests

Maxi Contieri ・ Apr 23 '23

#webdev #beginners #programming #tutorial

Code Smell 76 - Generic Assertions

Maxi Contieri ・ Jun 7 '21

#webdev #testing #testdev #tutorial

Context 💬

When you cram multiple assertions in a single test, failures become ambiguous.

You don’t know which part of the code caused the failure.

Imagine a test with five assertions fails at the second one - you never see whether assertions 3, 4, and 5 would have passed or failed, hiding additional defects.

Tests should be precise, easy to understand, and focused.

Each test should validate a single behavior and clearly communicate its purpose.

A single test function should test a single real world thing/concept.

You should not write long functions testing unrelated behaviors sequentially.

This usually hides the problem of heavy and coupled setups-

Sample Code 📖

Wrong ❌

def test_car_performance():
    car = Formula1Car("Red Bull")
    car.set_speed(320)
    assert car.speed == 320
    car.accelerate(10)
    assert car.speed == 330
    car.brake(50)
    assert car.speed == 280
    car.change_tire("soft")
    assert car.tire == "soft"

Right 👉

def test_set_speed():
    car = Formula1Car("Red Bull")
    car.set_speed(320)
    assert car.speed == 320, (
        f"Expected speed to be 320 km/h, "
        f"but got {car.speed} km/h"
    )

def test_accelerate():
    car = Formula1Car("Red Bull")
    car.set_speed(320)
    car.accelerate(10)
    assert car.speed == 330, (
        f"Expected speed to be 330 km/h "
        f"after accelerating by 10, "
        f"but got {car.speed} km/h"
    )

def test_brake():
    car = Formula1Car("Red Bull")
    car.set_speed(330)
    car.brake(50)
    assert car.speed == 280, (
        f"Expected speed to be 280 km/h "
        f"after braking by 50, "
        f"but got {car.speed} km/h"
    )

def test_change_tire():
    car = Formula1Car("Red Bull")
    car.change_tire("soft")
    assert car.tire == "soft", (
        f"Expected tire type to be 'soft', "
        f"but got '{car.tire}'"
    )