An introduction Effective Snapshot Testing on Android

Talk on Snapshot testing at Droidcon Berlin 2021 & Droidcon London 2021
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UI tests are a powerful tool to detect regression bugs. However, they are tedious to write and run very slow. But they are not the only tool we got to test the UI:
snapshot tests are some specific type of UI tests, that are not only easier to write but also run much faster than standard UI tests. They even help detect visual regression bugs that Espresso/UiAutomator tests cannot. Indeed, they are more widely used than UI tests by big companies such as Airbnb, with ≈ 30.000 snapshot tests, and Uber, with thousand of snapshot tests vs. a handful of UI tests, among others.

While there are plenty of resources about writing UI tests on Android, the same doesn't exist for snapshot tests. There is no guidance.

So, what is actually snapshot testing? how do you write a valuable snapshot test? what are the best practices? what are the pitfalls you have to take into account?

If you want to know how to get the most out of snapshot testing, come and join this tech talk. You will learn:
- what is snapshot testing and how your app can benefit from it
- how to decide what to snapshot test
- how to write your first meaningful snapshot test
- tips and tricks for better snapshot testing and what pitfalls to avoid
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Repo with code examples:
https://github.com/sergio-sastre/Road-To-Effective-Snapshot-Testing

Transcript

1. EFFECTIVE SNAPSHOT TESTING ON ANDROID BY SERGIO SASTRE AN INTRODUCTION TO
2. WHAT Snapshot testing is
3. Special type of UI tests take a screenshot of it, compare it to its reference we inflate a view, where and
4. Snapshot tests Ui tests thousand handful Source: "Building Mobile Apps at scale - 39 Engineering Challenges"
5. Snapshot tests Ui tests thousand handful ≈ 1 600 ≈ 500 Source: "Building Mobile Apps at scale - 39 Engineering Challenges"
6. Snapshot tests Ui tests thousand handful ≈ 1 600 ≈ 500 ≈ 2 300 ≈ 20 Source: "Building Mobile Apps at scale - 39 Engineering Challenges"
7. Snapshot tests Ui tests thousand handful ≈ 1 600 ≈ 500 ≈ 2 300 ≈ 20 ≈ 30 000 ? Source: "Building Mobile Apps at scale - 39 Engineering Challenges"
8. Ui tests Snapshot tests Icons made by “Freepik" from "Flaticon" writing speed
9. Ui tests Snapshot tests Icons made by “Freepik" from "Flaticon" writing speed
10. Ui tests Snapshot tests 5- 10 sec Icons made by “Freepik" from "Flaticon" writing speed
11. Ui tests Snapshot tests 5- 10 sec Icons made by “Freepik" from "Flaticon" writing speed
12. Ui tests Snapshot tests 5- 10 sec 1 sec < Icons made by “Freepik" from "Flaticon" writing speed
13. VS Snapshot 
 tests User interface tests
14. Snapshot 
 tests User interface tests VS
15. Snapshot 
 tests User interface tests +
16. Snapshot 
 tests User interface tests + (interaction) WHAT
17. Snapshot 
 tests User interface tests + (interaction) WHAT HOW (visuals)
18. MOTIVATION Snapshot test to
19. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
20. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
21. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
22. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
23. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
24. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs which will expand till the end of the line and …
25. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
26. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
27. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
28. Unexpected changes from library updates Spacing, styling, themes… Layout correctness Long text View overlapping Languages (RTL) System font size (HUGE) 1 2 3 visual bugs
29. Example
30. Layout validation
31. Layout validation
32. Settings Display Font size System font size > >
33. Example
34. Example
35. Font Size Largest 6,16% Small 8,06% Large 14,22% Default 71,56% TT Source: Android app with 80 000 monthly active users
36. Font Size Small 8,06% Default 71,56% TT 20, 38 % Large + Largest Source: Android app with 80 000 monthly active users
37. Do not trust Layout validation BUT Manual validation is hard
38. 1 Snapshot tests Use 2 Automate hard configs Catch regression bugs
39. WORKS HOW Snapshot testing
40. record AND verify
41. write test CI
42. record CI
43. = CI
44. CI new <code> PR +
45. approve CI
46. merge CI
47. CI new <code> PR verify
48. CI new <code> PR
49. CI new <code> PR
50. CI new <code> PR
51. CI new <code> PR verify
52. CI new <code> PR
53. CI new <code> PR
54. CI new <code> PR
55. CI Intentional change forgot to record regression bug YES NO
56. CI Emulator config matters D1 DN . . .
57. CI Emulator config matters = D1 DN = . . . = OR
58. CI Emulator config matters D1 = . . . DN = = OR
59. CI Emulator config matters D1 DN . . . = =
60. CI Emulator config matters = D1 = = . . . DN OR
61. CI Emulator config matters = D1 = = . . . DN OR
62. 1 2 More complex than standard testing Same emulator config everywhere process Snapshot testing
63. How to Snapshot test EFFECTIVELY
64. Example
65. Example
66. Dealing with asynchronicity Choosing test-worthy screen states More views, more prone to flakiness 1 2 3 snapshot testing full screen
67. Dealing with asynchronicity Choosing test-worthy screen states More views, more prone to flakiness 1 2 3 snapshot testing full screen
68. Dealing with asynchronicity Choosing test-worthy screen states More views, more prone to flakiness 1 2 3 snapshot testing full screen
69. Dealing with asynchronicity Choosing test-worthy screen states More views, more prone to flakiness 1 2 3 snapshot testing full screen
70. Dealing with asynchronicity Choosing test-worthy screen states More views, more prone to flakiness 1 2 3 snapshot testing full screen
71. start small & simple Header Training View Text view to memorise 1 split into smaller testable views
72. Header Training View Text view to memorise start small & simple 1 what to test
73. Header Training View Text view to memorise start small & simple 1 what to test
74. A B start small & simple 1 Identifying view states
75. A B start small & simple 1 Identifying view states
76. aim to break the layout 2 Identifying unhappy paths
77. aim to break the layout 2 Identifying unhappy paths thousand of words to train
78. aim to break the layout 2 Identifying unhappy paths thousand of words to train words to train for all 7 languages
79. aim to break the layout 2 Identifying unhappy paths thousand of words to train words to train for all 7 languages huge system font size
80. aim to break the layout 2 Identifying unhappy paths thousand of words to train words to train for all 7 languages huge system font size narrow screen
81. aim to break the layout 2 Identifying unhappy paths thousand of words to train words to train for all 7 languages huge system font size narrow screen
82. aim to break the layout 2 Identifying unhappy paths thousand of words to train words to train for all 7 languages huge system font size narrow screen trainingInfo =
 TrainingItem ( trainingByLang = wordsToTrainPerLang(999_999) , activeLangs = Language.values().toSet( ) ), TrainingTestItem( fontSize = FontScale.HUGE, viewWidth = ViewWidth.NARROW fun withWordsToTrainUnhappyPath() = )
 ) Mock Data
83. aim to break the layout 2 Identifying unhappy paths thousand of words to train words to train for all 7 languages huge system font size narrow screen trainingInfo =
 TrainingItem ( trainingByLang = wordsToTrainPerLang(999_999) , activeLangs = Language.values().toSet( ) ), TrainingTestItem( fontSize = FontScale.HUGE, viewWidth = ViewWidth.NARROW fun withWordsToTrainUnhappyPath() = )
 )
84. aim to break the layout 2 Identifying unhappy paths thousand of words to train words to train for all 7 languages huge system font size training 
 item narrow screen trainingInfo =
 TrainingItem ( trainingByLang = wordsToTrainPerLang(999_999) , activeLangs = Language.values().toSet( ) ), TrainingTestItem( fontSize = FontScale.HUGE, viewWidth = ViewWidth.NARROW ) fun withWordsToTrainUnhappyPath() = )
 )
85. aim to break the layout 2 Identifying unhappy paths thousand of words to train words to train for all 7 languages huge system font size narrow screen trainingInfo =
 TrainingItem ( trainingByLang = wordsToTrainPerLang(999_999) , activeLangs = Language.values().toSet( ) ), TrainingTestItem( fontSize = FontScale.HUGE, viewWidth = ViewWidth.NARROW )
 ) external fun withWordsToTrainUnhappyPath() =
86. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot private fun ScreenshotTest.snapViewHolder(testItem: TrainingTestItem, snapshotName: String){ val activity = FontsizeActivityScenario.launchWith(testItem.fontScale ) .waitForActivity(), val view = waitForView {
 val layout = activity.inflate(R.layout.training_row)
 TrainingViewHolder(layout).apply { bind ( trainingItem = testItem.trainingItem,
 languageClickedListener = null
 ) } } compareScreenshot {
 holder = view,
 widthInPx = testItem.viewWidth.widthInPx , name = snapshotName
 } } Test itself
87. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot private fun ScreenshotTest.snapViewHolder(testItem: TrainingTestItem, snapshotName: String){ val activity = FontsizeActivityScenario.launchWith(testItem.fontScale ) .waitForActivity(), val view = waitForView {
 val layout = activity.inflate(R.layout.training_row)
 TrainingViewHolder(layout).apply { bind ( trainingItem = testItem.trainingItem,
 languageClickedListener = null
 ) } } compareScreenshot {
 holder = view,
 widthInPx = testItem.viewWidth.widthInPx , name = snapshotName
 } }
88. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot private fun ScreenshotTest.snapViewHolder(testItem: TrainingTestItem, snapshotName: String){ val activity = FontsizeActivityScenario.launchWith(testItem.fontScale ) .waitForActivity(), val view = waitForView {
 val layout = activity.inflate(R.layout.training_row)
 TrainingViewHolder(layout).apply { bind ( trainingItem = testItem.trainingItem,
 languageClickedListener = null
 ) } } compareScreenshot {
 holder = view,
 widthInPx = testItem.viewWidth.widthInPx , name = snapshotName
 } } Wait for 
 Ui thread 
 idle + launch 
 ActivityScenario
89. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot private fun ScreenshotTest.snapViewHolder(testItem: TrainingTestItem, snapshotName: String){ val activity = FontsizeActivityScenario.launchWith(testItem.fontScale ) .waitForActivity(), val view = waitForView {
 val layout = activity.inflate(R.layout.training_row)
 TrainingViewHolder(layout).apply { bind ( trainingItem = testItem.trainingItem,
 languageClickedListener = null
 ) } } compareScreenshot {
 holder = view,
 widthInPx = testItem.viewWidth.widthInPx , name = snapshotName
 } } Inflate view 
 & bind data Wait for 
 Ui thread 
 idle +
90. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot private fun ScreenshotTest.snapViewHolder(testItem: TrainingTestItem, snapshotName: String){ val activity = FontsizeActivityScenario.launchWith(testItem.fontScale ) .waitForActivity(), val view = waitForView {
 val layout = activity.inflate(R.layout.training_row)
 TrainingViewHolder(layout).apply { bind ( trainingItem = testItem.trainingItem,
 languageClickedListener = null
 ) } } compareScreenshot {
 holder = view,
 widthInPx = testItem.viewWidth.widthInPx , name = snapshotName
 } } record screenshot
91. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot private fun ScreenshotTest.snapViewHolder(testItem: TrainingTestItem, snapshotName: String){ val activity = FontsizeActivityScenario.launchWith(testItem.fontScale ) .waitForActivity(), val view = waitForView {
 val layout = activity.inflate(R.layout.training_row)
 TrainingViewHolder(layout).apply { bind ( trainingItem = testItem.trainingItem,
 languageClickedListener = null
 ) } } compareScreenshot {
 holder = view,
 widthInPx = testItem.viewWidth.widthInPx , name = snapshotName
 } }
92. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(private val testItem: TrainingTestItem): ScreenshotTest{ companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath()
 .. . )
 } @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } Parameterized 
 tests
93. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(private val testItem: TrainingTestItem): ScreenshotTest{ companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath()
 .. . )
 } @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) }
94. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(private val testItem: TrainingTestItem): ScreenshotTest{ companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath()
 .. . )
 } @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } set 
 Runner
95. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(private val testItem: TrainingTestItem): ScreenshotTest{ companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath()
 .. . )
 } @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } generate 
 test data
96. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(private val testItem: TrainingTestItem): ScreenshotTest{ companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath()
 .. . )
 } @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } test with 
 parameter
97. aim to break the layout 2 writing the snapshot test with pedrovgs/Shot @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(private val testItem: TrainingTestItem): ScreenshotTest{ companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath()
 .. . )
 } @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) }
98. aim to break the layout 2 thousand of words to train words to train for all 7 languages huge system font size narrow screen recording unhappy path
99. aim to break the layout 2 @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(private val testItem: TrainingTestItem): ScreenshotTest{ companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath()
 .. . )
 } @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } recording happy and unhappy paths
100. aim to break the layout 2 @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(private val testItem: TrainingTestItem): ScreenshotTest{ companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(), withWordsToTrainHappyPath()
 withoutWordsToTrainUnhappyPath(), withoutWordsToTrainHappyPath( ) )
 } @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } recording happy and unhappy paths
101. aim to break the layout 2 recording happy and unhappy paths without WordsToTrain HappyPath() with WordsToTrain HappyPath() with WordsToTrain UnhappyPath() without WordsToTrain UnhappyPath()
102. group tests by relevance 3
103. 2’ 100 happy + unhappy group tests by relevance 3 100%
104. 2’ 4’ 200 100 happy + unhappy group tests by relevance 3 100%
105. 2’ 4’ 8’ 400 200 100 happy + unhappy group tests by relevance 3 100%
106. 2’ 4’ 8’ 16’ 800 400 200 100 happy + unhappy group tests by relevance 3 100%
107. 2’ 4’ 8’ 16’ … 800 400 200 100 happy + unhappy 100% group tests by relevance 3
108. 2’ 4’ 8’ 16’ 800 400 200 100 group tests by relevance 3 unhappy happy 90 - 100% 5 - 20% …
109. 2’ … 1’ 3’ 40 80 160 320 6’ unhappy happy 90 - 100% 5 - 20% group tests by relevance 3
110. daily builds night build
111. night build run happy path tests ONLY catch most important bugs run on every PR daily builds
112. night build run happy path tests ONLY catch most important bugs run on every PR run unhappy path tests ONLY catch less important bugs run once a day daily builds
113. night build run happy path tests ONLY catch most important bugs run on every PR run unhappy path tests ONLY catch less important bugs run once a day daily builds fast development cycles
114. 3 unhappy vs. happy path @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } group tests by relevance companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(), withWordsToTrainHappyPath()
 withoutWordsToTrainUnhappyPath(), withoutWordsToTrainHappyPath( ) )
 } Filtered parameterized 
 tests
115. 3 unhappy vs. happy path @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } group tests by relevance companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(), withWordsToTrainHappyPath()
 withoutWordsToTrainUnhappyPath(), withoutWordsToTrainHappyPath( ) )
 }
116. 3 @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } group tests by relevance companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(), withWordsToTrainHappyPath()
 withoutWordsToTrainUnhappyPath(), withoutWordsToTrainHappyPath( ) )
 } unhappy vs. happy path
117. 3 @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } group tests by relevance companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(),
 withoutWordsToTrainUnhappyPath( ) )
 } companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainHappyPath()
 withoutWordsToTrainHappyPath( ) )
 } @RunWith(Parameterized::class)
 class TrainingItemHappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } unhappy vs. happy path
118. 3 @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } group tests by relevance companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(),
 withoutWordsToTrainUnhappyPath( ) )
 } companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainHappyPath()
 withoutWordsToTrainHappyPath( ) )
 } @RunWith(Parameterized::class)
 class TrainingItemHappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } unhappy vs. happy path
119. 3 @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @UnhappyPat h @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } group tests by relevance companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(),
 withoutWordsToTrainUnhappyPath( ) )
 } companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainHappyPath()
 withoutWordsToTrainHappyPath( ) )
 } @RunWith(Parameterized::class)
 class TrainingItemHappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @HappyPat h @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } unhappy vs. happy path
120. 3 @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @UnhappyPat h @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } group tests by relevance companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(),
 withoutWordsToTrainUnhappyPath( ) )
 } companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainHappyPath()
 withoutWordsToTrainHappyPath( ) )
 } @RunWith(Parameterized::class)
 class TrainingItemHappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @HappyPat h @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } = path.to.annotation.UnhappyPath -Pandroid.testIntrumentationRunnerArguments.annotation ./gradlew -Precord unhappy vs. happy path
121. 3 @RunWith(Parameterized::class)
 class TrainingItemUnhappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @UnhappyPat h @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } group tests by relevance companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainUnhappyPath(),
 withoutWordsToTrainUnhappyPath( ) )
 } companion object {
 @JvmStatic
 @Parameterized.Parameter s fun testData(): Array<TrainingTestItem> = arrayOf ( withWordsToTrainHappyPath()
 withoutWordsToTrainHappyPath( ) )
 } @RunWith(Parameterized::class)
 class TrainingItemHappyPath(
 private val testItem: TrainingTestItem
 ): ScreenshotTest{ @HappyPat h @Test
 fun snapTrainingItem(){ snapViewHolder(testItem)
 ) } = path.to.annotation.HappyPath -Pandroid.testIntrumentationRunnerArguments.annotation ./gradlew -Precord unhappy vs. happy path
122. 1 Snapshot testing effectively 2 Start small & simple Aim to break the layout 3 Group tests by relevance
123. attention for your THANKS
124. code blogs @SergioSastre @sergio-sastre @sergio-sastre @Gio_Sastre Sergio Sastre Flórez Lead & Senior Android developer appdev.de