8ef9a27a97
* Documention: Document Status of Percy * Apply suggestions from code review Co-authored-by: Vaidehi Joshi <vaidehi.sj@gmail.com> Co-authored-by: Vaidehi Joshi <vaidehi.sj@gmail.com>
47 lines
2.2 KiB
Markdown
47 lines
2.2 KiB
Markdown
---
|
|
title: Regression Testing
|
|
---
|
|
|
|
# Regression Testing
|
|
|
|
Regression testing is a technique for detecting breaking changes over time in a
|
|
codebase.
|
|
|
|
Proper Regression testing is one of the most powerful tools in a programmer's
|
|
arsenal for avoiding the bugs that crop up as a project grows in size.
|
|
|
|
Generally speaking, Regression testing is accomplished by a combination of
|
|
[Acceptance tests][acceptance_tests] and [Integration tests][integration_tests]
|
|
performed on areas where bugs have been found in the past. As it happens,
|
|
software bugs tend to exist in groups; writing tests around buggy code will
|
|
almost always uncover new bugs as code evolves.
|
|
|
|
The practice of Regression testing usually takes place after code has been
|
|
written, and is used to detect if recent changes have introduced new bugs by
|
|
breaking previously functional software.
|
|
|
|
There is no perfect prescribed method for Regression testing, and it has evolved
|
|
with the introduction of [Continuous Integration][ci] practices like the ones
|
|
that DEV uses. However, CI doesn't replace the need for Regression testing.
|
|
Regression tests should still be added to the codebase when bugs are discovered.
|
|
|
|
If you submit a bug patch to the DEV application, you might be asked to write a
|
|
Regression test around your patch to help warn future DEV contributors if that
|
|
bug ever makes another appearance. This practice has the added benefit of
|
|
helping to ensure your patch fixes the bug.
|
|
|
|
[acceptance_tests]: /tests/acceptance-tests/
|
|
[integration_tests]: /tests/integration-tests/
|
|
[ci]: /deployment/
|
|
|
|
# [Percy](https://percy.io/)
|
|
|
|
Percy is a tool that can be used to do visual regression testing. Percy renders
|
|
and compares snapshots across browsers and screens to detect, highlight, and
|
|
group visual differences. This allows users to quickly find visual regression issues. Currently,
|
|
**Percy is inactive in our test suite** due to some integration issues. We are
|
|
not sure if we will try to reimplement it in the future so for now we have
|
|
decided to leave the code as is. You will notice `Percy.snapshot` being called
|
|
in multiple tests. That method has been stubbed in our `rails_helper.rb` file to ensure that
|
|
we don't waste resources taking snapshots. You will also notice some specs that
|
|
only take Percy snapshots have been commented out.
|