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docs: better pre-amble for testing doc

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dannyrb 2019-08-21 23:06:30 -04:00
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docs/latest/contributing/testing.md
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@ -9,20 +9,20 @@ different. But do you know why we write tests? Do you know when to write one, or
what kind of test to write? How do you know if a test is a _"good"_ test? This
document's goal is to give you the tools you need to make those determinations.
Okay. So why do we write tests? To increase our... :drum::
Okay. So why do we write tests? To increase our... **CONFIDENCE**
**CONFIDENCE**
- If I do a large refactor, does everything still work?
- If I changed some critical piece of code, is it safe to push to production?
> I want to be confident that the code I'm writing... won't break the app that I
> have running in production. So whatever I do, I want to make sure that the
> kinds of tests I write bring me the most confidence possible and I need to be
> cognizant of the trade-offs I'm making when testing. - Kent C. Dodds
Gaining the confidence we need to answer these questions after every change is
costly. Good tests allow us to answer them without manual regression testing.
What and how we choose to test to build that confidence is nuanced.
## Kinds of Tests
Test's buy us confidence, but not all tests are created equal. Each kind of test
has a different cost to write and maintain. An expensive test is worth it if it
gives us confidance that a payment is processed, but it may not be the best
gives us confidence that a payment is processed, but it may not be the best
choice for asserting an element's border color.
| Test Type | Example | Speed | Cost |
@ -32,6 +32,10 @@ choice for asserting an element's border color.
| Integration | Clicking "Sign In", navigates to the dashboard (mocked network requests) | :running: Okay | :money_with_wings::money_with_wings::money_with_wings: |
| End-to-end | Clicking "Sign In", navigates to the dashboard (no mocks) | :turtle: Slow | :money_with_wings::money_with_wings::money_with_wings::money_with_wings: |
- :rocket: Speed: How quickly tests run
- :money_with_wings: Cost: Time to write, and to debug when broken (more points
of failure)
### Static Code Analysis
Modern tooling gives us this "for free". It can catch invalid regular
@ -66,23 +70,21 @@ Where it falls short: That you're calling a dependency appropriately.
### Integration Tests
Integration tests take things one step further. You
Where it falls short: That you're passing the right data to your backend.
We write integration tests to gain confidence that several units work together.
Generally, we want to mock as little as possible for these tests. In practice,
this means only mocking network requests.
### End-to-End Tests
These are the most expensive tests to write and maintain. Largely because, when
they fail, they have the largest number of potential points of failure. So why
do we write them? Because they also buy us the most confidance.
do we write them? Because they also buy us the most confidence.
We should reserve end-to-end tests for mission critical features. A good example
is testing user authentication. If a user can't sign in to your application,
it's an emergency. Having a high degree of confidance that users can always
it's an emergency. Having a high degree of confidence that users can always
authenticate is very valuable.
Where it falls short:
#### When should we test?
Mission critical features and functionality, or to cover a large breadth of
@ -91,11 +93,6 @@ feature `X` or scenario `Y`? Open an issue and let's discuss.
## Further Reading
Okay, so hopefully you have more confidance in your understanding of _why_ we
test, and the trade-offs we weigh when determining what kind of test should be
written. For the _how_, check out some of the links below, or read some of the
existing tests in this repository.
### General
- [Assert(js) Conf 2018 Talks][assert-js-talks]