06 DRY (Don’t Repeat Yourself)

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06 DRY (Don't Repeat Yourself)


In this video, learn about the DRY (Don’t Repeat Yourself) principle and how it
can affect end-to-end tests. After watching this video, you will be able to
create reusable helpers for data setup in your own Cypress end-to-end tests.

00:00
(upbeat music)
00:03
Welcome back
00:04
to Test Double’s intro course
00:06
on end-to-end testing with Cypress.
00:08
In the previous video,
00:09
you added another real world happy path test,
00:13
learning about other useful commands in Cypress,
00:16
and why not to share persisted state between tests.
00:19
In this video,
00:20
you will learn about the DRY principle,
00:24
learn how duplication can affect tests,
00:27
and reduce some duplication
00:28
in the existing yams test suite.
00:31
DRY is a common acronym used in software development.
00:35
It stands for, “Don’t Repeat Yourself.”
00:38
The basic premise behind it
00:40
is to make code more maintainable
00:42
by reducing duplicated code and concepts.
00:45
When you need to make a change
00:46
to a piece of duplicated code,
00:48
you have to update that code
00:50
in all the places it’s replicated.
00:52
That takes more time
00:53
and can lead to unintended bugs
00:55
if you miss updating a place.
00:58
So developers use various techniques
01:00
to manage code needed in multiple places
01:03
with abstractions that reduce duplication
01:06
and are more maintainable.
01:08
Whether it’s duplicated setup code
01:10
or redundant tests,
01:12
duplication poses problems in tests as well,
01:15
making test code harder
01:16
to maintain and understand
01:18
as well as slowing down test suites.
01:21
To see what I mean,
01:22
let’s fix one glaring example of duplication
01:25
in the current yams test suite.
01:27
Boot up the back-end server Cypress environment,
01:30
front-end dev server, and Cypress itself.
01:34
Also, ensure you’re running
01:35
the tasks.spec.js file in Cypress.
01:40
Inside the spec file,
01:41
you have three spots
01:42
where you duplicate the same code
01:44
to generate a unique task title
01:47
by appending a timestamp.
01:48
Let’s extract that logic
01:50
into a reusable function
01:52
so you don’t have to repeat it everywhere.
01:54
At the top of the test file above describe,
01:57
add a helper function called uniqueTitle.
02:00
The function accepts the title as an argument
02:03
and returns a version of the title
02:05
with the current timestamp appended.
02:08
Update the spots
02:09
where you manually add the timestamp
02:10
to use this function,
02:16
and then save the file
02:17
to make sure the tests still pass.
02:20
Now, if you ever wanna update the core logic
02:22
of generating a unique title,
02:25
you’ll only need to make that change in one place.
02:28
Let’s recap what you learned in this video.
02:31
You learned about the DRY principle,
02:33
you learned how duplication affects tests,
02:36
and you reduced some duplication
02:38
in the existing yams test suite
02:40
by creating a reusable function
02:42
to generate unique tasks titles for tests.
02:45
You are now ready to DRY up your own tests,
02:48
but let’s take your knowledge further.
02:50
In the next video,
02:51
you will learn how redundant tests
02:53
can violate the DRY principle
02:55
and slow down test suites.
02:58
You will discover how to combine tests
03:00
to reduce duplication and speed up tests.
03:03
(upbeat music)

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