Detecting Process Death issues with Maestro
After explaining what System-initiated Process Death is, showing how to detect it manually and automate detection with Appium, I’d like to demonstrate how to automate detection this time with Maestro, a relatively new Automation tool! 🎉
What is Maestro?
Maestro is a command line tool that allows us to run end-to-end UI tests, written in a simple YAML format.
Run the following command to install Maestro on Mac OS, Linux or Windows (WSL):
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curl -Ls "https://get.maestro.mobile.dev" | bash
Using Maestro
Let’s go back to the demo project containing a fragment-based app built with two screens:
- A first screen to enter a name called EnterNameFragment
- Second one to show that information called ShowInfoFragment
- To pass a name value between those screens, a Singleton called DataHolder is used, which will lose its value after System-initiated Process Death.
A file called happy-flow.yaml in a .maestro folder will contain the following maestro commands:
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appId: dev.galex.process.death.demo
---
- launchApp
- tapOn:
id: "dev.galex.process.death.demo:id/enter_name"
- inputText: "John Doe"
- tapOn:
id: "dev.galex.process.death.demo:id/next"
- assertVisible:
id: "dev.galex.process.death.demo:id/show_name"
text: "Name = John Doe"
enabled: true
- stopApp
We’ll run this test with the following command, from the demo project root folder:
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maestro test .maestro/happy-flow.yaml
The result of running this test will show a successful run for our test:
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Running on 41161FDJG002EG
║
║ > Flow
║
║ ✅ Launch app "dev.galex.process.death.demo"
║ ✅ Tap on id: dev.galex.process.death.demo:id/enter_name
║ ✅ Input text John Doe
║ ✅ Tap on id: dev.galex.process.death.demo:id/next
║ ✅ Assert that "Name = John Doe", id: dev.galex.process.death.demo:id/show_name is visible
║ ✅ Stop dev.galex.process.death.demo
║
Triggering The Issue with Maestro
Since version 1.37.0, which was finally released last week, Maestro offers the ability to trigger System-initiated Process Death using a command called killApp which I was very happy to introduce into to the Maestro project. Yay to Open-Source! 🎉
We’ll call this file appropriately detect-process-death-issue.yaml:
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appId: dev.galex.process.death.demo
---
- launchApp
- tapOn:
id: "dev.galex.process.death.demo:id/enter_name"
- inputText: "John Doe"
- tapOn:
id: "dev.galex.process.death.demo:id/next"
- assertVisible:
id: "dev.galex.process.death.demo:id/show_name"
text: "Name = John Doe"
enabled: true
- pressKey: Home
- killApp
- launchApp:
stopApp: false
- assertVisible:
id: "dev.galex.process.death.demo:id/show_name"
text: "Name = John Doe"
label: "Assert that \"Name = John Doe\" meaning the screen kept its data after System-initiated Process Death"
enabled: true
- stopApp
Let’s pay attention to the part that helps us reproduce the issue, with explanations in comments:
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- pressKey: Home # Puts the app into the background
- killApp # Kills the app (adb shell am kill)
- launchApp: # Relaunches the app
stopApp: false # Without adb shell am stop
We’ll run this test with the following command:
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maestro test .maestro/detect-process-death-issue.yaml
The result of running this test will fail:
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Running on 41161FDJG002EG
║
║ > Flow
║
║ ✅ Launch app "dev.galex.process.death.demo"
║ ✅ Tap on id: dev.galex.process.death.demo:id/enter_name
║ ✅ Input text John Doe
║ ✅ Tap on id: dev.galex.process.death.demo:id/next
║ ✅ Assert that "Name = John Doe", id: dev.galex.process.death.demo:id/show_name is visible
║ ✅ Press Home key
║ ✅ Kill dev.galex.process.death.demo
║ ✅ Launch app "dev.galex.process.death.demo" without stopping app
║ ❌ Assert that "Name = John Doe" meaning the screen kept its data after System-initiated Process Death
║ 🔲 Stop dev.galex.process.death.demo
║
Assertion is false: "Name = John Doe", id: dev.galex.process.death.demo:id/show_name is visible
==== Debug output (logs & screenshots) ====
/Users/galex/.maestro/tests/<date>
Perfect! We’ve successfully detected the System-initiated Process Death issue with Maestro! 🎉
In the generated folder /Users/galex/.maestro/tests/<date> we’ll find the screenshots taken by Maestro, showing the ShowInfoFragment screen with the text Name = null instead of Name = John Doe:
.png)
Improving our Maestro Test
To be able to re-use the commands that allow us to trigger System-initiated Process Death, we can put them in another .yaml file named trigger-process-death.yaml:
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appId: dev.galex.process.death.demo
---
- pressKey: Home # Puts the app into the background
- killApp # Kills the app (adb shell am kill)
- launchApp: # Relaunches the app
stopApp: false # Without adb shell am stop
And use the runFlow command in our original detect-process-death-issue.yaml test to include it:
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appId: dev.galex.process.death.demo
---
- launchApp
- tapOn:
id: "dev.galex.process.death.demo:id/enter_name"
- inputText: "John Doe"
- tapOn:
id: "dev.galex.process.death.demo:id/next"
- assertVisible:
id: "dev.galex.process.death.demo:id/show_name"
text: "Name = John Doe"
enabled: true
- runFlow: trigger-process-death.yaml
- assertVisible:
id: "dev.galex.process.death.demo:id/show_name"
text: "Name = John Doe"
label: "Assert that \"Name = John Doe\" meaning the screen kept its data after System-initiated Process Death"
enabled: true
- stopApp
The output of running detect-process-death-issue.yaml will look almost the same as before:
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Running on 41161FDJG002EG
║
║ > Flow
║
║ ✅ Launch app "dev.galex.process.death.demo"
║ ✅ Tap on id: dev.galex.process.death.demo:id/enter_name
║ ✅ Input text John Doe
║ ✅ Tap on id: dev.galex.process.death.demo:id/next
║ ✅ Assert that "Name = John Doe", id: dev.galex.process.death.demo:id/show_name is visible
║ ✅ Run trigger-process-death.yaml
║ ❌ Assert that "Name = John Doe" meaning the screen kept its data after System-initiated Process Death
║ 🔲 Stop dev.galex.process.death.demo
║
Assertion is false: "Name = John Doe", id: dev.galex.process.death.demo:id/show_name is visible
==== Debug output (logs & screenshots) ====
/Users/galex/.maestro/tests/<date>
We’ve improved the re-usability of our detecting method!
Conclusion
We’ve successfully detected the System-initiated Process Death issue with Maestro! 💪 It makes the whole ordeal so easy I seriously think an E2E Maestro test should be a part of every feature we build to ensure its quality and robustness! 🚀
Let me know what you think or if you have any questions in the comments! 📝
Happy testing! 🧪