Automated testing in the real world

https://slides.com/paquicalabria/automated-testing-ada-js/

@zurribulle

@adabcnjs

https://adajs.cat

https://github.com/FCalabria

Everybody hates writing tests

Universal truth of testing #1:

But automated tests are one of the best development tools

So let's try to improve at using them. For our own good.

First of all, let's review some basic definitions:

An isolated unit of code is tested. The rest is mocked (faked)

Unit test

The connection between two or more components is tested. There are still mocked parts

Integration test

All the components involved are tested at once. No mocks.

End to end test

are useful in their own way

All of them

follow the same methodologies

have common good practices

execution time

Main differences

reliability

specificity

% of code that has been executed during the testing

Code coverage

% of paths that have been taken during the testing

Branches coverage

coverage

is 

a 

LIE

Although, coverage reports by file can be really useful

Bad reasons to write tests

Company rules say so

A red report looks bad on Sonar

You are supposed to do it, aren't you?

Bad reasons lead to bad tests

A few good tests are better than a lot of useless tests

Good reasons to write tests

Easier refactoring

Better understanding of the requirements

More robust components

Documentation for other developers

Less buggy Continuous Delivery

Arguments for business to sell the project

Improve the stakeholders's trust

Not reasons

Tests are a development tool

Universal truth of testing #2:

• When you read the statement, you know what the component should do

• Each test checks one thing, not more

• If the code does not do what is stated, the test fails

• If the code does what is stated, the test always passes

• When a test fails, you can easily know why

Spotting good tests

What to test

What is going to be more useful?

Stick to a reasonable time

Unit test:

Difficult first Vs easy first

Some tips

• Minimum: The happy path, unless it's trivial

• Don't forget error management, specially in the backend

• Be careful with branches involving business rules

• Don't get obsessed with the coverage

• Tests have to be useful, not mandatory

My method

Follow at your own risk

Compatible with (but is not) TDD

1. Initial set up

Create the component in a testing environment

Mocks are ready

• CLIs and related tools help a lot

• Careful with automated dependency injection and undesired http calls

• Clean environment on each test: reset mocks, clean browser storage, etc

• Don't mock the element to test, duh!

A mock missed today, is a headache tomorrow

Universal truth of testing #3:

2. Statements + analisys

Define groups of testable code

• Testing order is important

• Unit/integration tests: should be the public functions

• E2E tests: A step in the path, or a part of the view.

3. Test cases + expectations

How should this part of the app behave?

• Try to think about all the corner cases

• What would you like to check when the code breaks?

• If you need to write "and" in the title, it's better to split it in two

• Again, order is important

4. Make it pass

Fire the function. Then, add the needed set up

• Modify mocks to the test needs

• Add specific setup

• Don't forget to clean afterwards

Cleaner code = easier tests

Universal truth of testing #4:

5. Make it fail

• Does the test fail when and how it's supposed to fail?

• E2E: screenshots are the best!

• https://stryker-mutator.io

Write your tests like the next developer is a crazy man with an axe

Resources

• Asynchronous testing gotchas

• The way of Testivus

• Good tests vs bad tests

• Why most unit testing is waste (summary)

• How about everyone gets unit testing wrong

Questions time!