In this SauceCon 2019 talk, Wim discusses why he used ResembleJS as a core visual comparison solution, the things he learned about Appium in the process (pro tips!), the differences between iOS and Android and how he managed to solve this in one cross-platform solution.

1. Building Your Own Native App
Visual Testing Module with Appium
Wim Selles,
Sr. Solutions Architect @Sauce Labs

2. It’s not about me
! :@wswebcreation
" : https://github.com/wswebcreation

3. Idea

4. Idea

5. Requirements
• Native App support
• Cross platform
• Integrate WebdriverIO
• Paid tools === trial first
• Support blockouts
• Support element screenshots/bounding box
For a visual regression/testing solution

6. Blockouts
Status-/navigation-/
home indicator bar
Why…?
Animations Dynamic text

7. Research
Visual regression / testing for Native Apps
iOSSnapshotTestCase
Nakal
sightr.io
screenshot-tests-for-android

8. Result
Visual regression / testing for Native Apps
Requirements
screenshot-tests-
for-android
iOSSnapshot
TestCase
Nakal sightr.io VisWiz Applitools
Native apps support Yes Yes Yes Yes Yes Yes
WebdriverIO support
- JS
- No extra environment
dependencies
No No No No Yes
Not for
native apps
Trial? Open source Open source Open source Beta Yes Yes
Image diff Yes, basic Yes, basic Yes Yes Yes, basic Yes, extensive
Blockouts No No Yes and no No no Yes
Element screenshots No No No No No No
Bounding box No No No No No Yes

9. Result
Visual regression / testing for Native Apps
Requirements
screenshot-tests-
for-android
iOSSnapshot
TestCase
Nakal sightr.io VisWiz Applitools
Native apps support Yes Yes Yes Yes Yes Yes
WebdriverIO support
- JS
- No extra environment
dependencies
No No No No Yes
Not for
native apps
Trial? Open source Open source Open source Beta Yes Yes
Image diff Yes, basic Yes, basic Yes Yes Yes, basic Yes, extensive
Blockouts No No Yes and no No no Yes
Element screenshots No No No No No No
Bounding box No No No No No Yes

10. Result
Visual regression / testing for Native Apps
Requirements
screenshot-tests-
for-android
iOSSnapshot
TestCase
Nakal sightr.io VisWiz Applitools
Native apps support Yes Yes Yes Yes Yes Yes
WebdriverIO support
- JS
- No extra environment
dependencies
No No No No Yes
Not for
native apps
Trial? Open source Open source Open source Beta Yes Yes
Image diff Yes, basic Yes, basic Yes Yes Yes, basic Yes, extensive
Blockouts No No Yes and no No no Yes
Element screenshots No No No No No No
Bounding box No No No No No Yes

11. Result
Visual regression / testing for Native Apps
Requirements
screenshot-tests-
for-android
iOSSnapshot
TestCase
Nakal sightr.io VisWiz Applitools
Native apps support Yes Yes Yes Yes Yes Yes
WebdriverIO support
- JS
- No extra environment
dependencies
No No No No Yes
Not for
native apps
Trial? Open source Open source Open source Beta Yes Yes
Image diff Yes, basic Yes, basic Yes Yes Yes, basic Yes, extensive
Blockouts No No Yes and no No no Yes
Element screenshots No No No No No No
Bounding box No No No No No Yes

12. Result
Visual regression / testing for Native Apps
Requirements
screenshot-tests-
for-android
iOSSnapshot
TestCase
Nakal sightr.io VisWiz Applitools
Native apps support Yes Yes Yes Yes Yes Yes
WebdriverIO support
- JS
- No extra environment
dependencies
No No No No Yes
Not for
native apps
Trial? Open source Open source Open source Beta Yes Yes
Image diff Yes, basic Yes, basic Yes Yes Yes, basic Yes, extensive
Blockouts No No Yes and no No no Yes
Element screenshots No No No No No No
Bounding box No No No No No Yes
?

13. Conclusion
What to do?

14. Logic
Who should do what?
Requirements Module Comparison engine
Actively maintained - Yes
Environment dependencies No No
Blockout(s) Yes, determine and provide Yes
Element screenshot Yes -
Create baseline Yes -
Screenshots per device Yes -
Support compare options
(for example antialiasing)
Yes Yes

15. Logic
Who should do what?
Requirements Module Comparison engine
Actively maintained - Yes
Environment dependencies No No
Blockout(s) Yes, determine and provide Yes
Element screenshot Yes -
Create baseline Yes -
Screenshots per device Yes -
Support compare options
(for example antialiasing)
Yes Yes

16. JavaScript pixel-by-pixel libraries
js-imagediff
image-diff
Rembrandt.JS
LooksSame
pixelmatch
node-opencv
img-diff-js
Pixel-Diff
Resemble.JS

17. JavaScript pixel-by-pixel libraries
js-imagediff
image-diff
Rembrandt.JS
LooksSame
pixelmatch
node-opencv
img-diff-js
Pixel-Diff
Resemble.JS

18. JavaScript pixel-by-pixel libraries
js-imagediff
image-diff
Rembrandt.JS
LooksSame
pixelmatch
node-opencv
img-diff-js
Pixel-Diff
Resemble.JS

19. JavaScript pixel-by-pixel libraries
js-imagediff
image-diff
Rembrandt.JS
LooksSame
pixelmatch
node-opencv
img-diff-js
Pixel-Diff
Resemble.JS

20. JavaScript pixel-by-pixel libraries
js-imagediff
image-diff
Rembrandt.JS
LooksSame
pixelmatch
node-opencv
img-diff-js
Pixel-Diff
Resemble.JS

21. Conclusion

22. Conclusion

23. • saveScreen
What should it do

24. • saveScreen
• compareScreen
What should it do

25. • saveScreen
• compareScreen
• saveElement
What should it do

26. • saveScreen
• compareScreen
• saveElement
• compareElement
What should it do

27. saveScreen
What should it do?

28. compareScreen
Where could it go wrong, where could it cause flakiness?
Navigation bar Home bar indicatorStatus bar

29. Status bar
• Android and iOS differ in height
• iOS OS versions / devices differ
• Android OS versions / devices differ
• Cross platform / device solution

40. Navigation bar
• Android OS versions / devices differ
• Not each device has a tool/navigation bar
• Cross device solution
For Android

42. Home bar indicator
● Currently 2 sizes
● The behaviour can be adjusted
iPhone X series

44. saveElement

45. saveElement

46. saveElement

47. saveElement

48. compareElement
● Comparing (options) the same
as for compareScreen
● Element block-outs more complex

49. Use case
React Native
0.54
React Native
0.57

50. Use case
React Native
0.54
React Native
0.57

51. Use case

52. Disclaimer
Cons
● Basic comparison
● Impact on project size
● Limited blockout options
● No dashboard
Pro’s
● Open Source
● The (module) logic is easy
● Easy cross platform/device blockout logic
driver.compareScreen(
'compareScreen-elementBlockOuts', {
elementBlockOuts: [
// block out element 1
{ element: LoginScreen.loginButton },
// block out element 2 with margin
{ element: LoginScreen.email, margin: 50},
],
}
);

53. Want to use it?
https://github.com/wswebcreation/wdio-native-app-compare

54. Want to use it?

55. Thank you.