Some sprints ago, me and my team, during the sprint planning event, we were discussing the implementation of touchID on login in our React Native App.

I have started the POC of Biometrics (as I have never done it in the past), so I could have a clear view if would be possible to automate on Android platform using an Android 9.0 emulator.

After a bit of research, I saw all solutions that I have found on the web (i don't know if I've missed any, sorry for that) are instructed how to add a fingerprint manually and then using an adb command to pass it in the biometric alert and make the valid login.

Then I have checked if there are any adb commands that will make my life easier and BOOM....

With the power of Appium and WebdriverIO!!!

I came to the following solution:

First of all, I took notes on how those actions can be done manually:

• Go to Android Settings.
• Tap on Security & Location.
• Add Screen Lock, there are several types such as Pin, Pattern, Swipe, Password (I chose Pin).
• You have to follow the wizard of your choice.
• Then you tap on Fingerprint.
• There is again a wizard to follow
• Then I should open my app
• Go to Login screen and provide the fingerprint on Biometrics Alert

That's it! Now let's automate!

I have configured Appium with --relaxed-security flag in wdio.conf.js, so Appium can accept adb commands

services: [
        [
            'appium',
            {
              args: {
                  '--relaxed-security': true
            },
              command: 'appium'
            },
        ],
    ]

Next, the real fun starts!

The first 4 manual steps I found out that could be done like this:

browser.execute('mobile: shell', {
  command: 'am start -a android.settings.SECURITY_SETTINGS && locksettings set-pin 1234'
});

After that, as I am still in Android Security Settings I need to tap on Fingerprint using Appium desktop I found the selector and click on it:

$('android=new UiSelector().text("Fingerprint")').click();

The Fingerprint wizard is open and there is a Next button, using the same approach as above:

$('android=new UiSelector().resourceId("com.android.settings:id/fingerprint_next_button")').click();     

I need to provide the pin I have setup on Screen Lock and tap keyboard's Done button:

browser.execute('mobile: shell', { 
  command: 'input text 1234 && input keyevent 66'
}); 

Then the wizard prompts the user to touch the sensor (this should be done 3 times), here Appium provides us the .fingerPrint(fingerprintId) method, that actually executes an adb command adb -e emu finger touch fingerprintId:

for (let i = 1; i <= 3; i++) {
    browser.pause(1500);
    browser.fingerPrint(1);
  }

The final step of the wizard is to tap on Done button:

$('android=new UiSelector().resourceId("com.android.settings:id/next_button")').click();

After that, we should start our App. This is again provided by Appium using .startActivity("com.example", "ActivityName"); method. In my example is:

browser.startActivity('com.reactnativesampleapp', 'com.reactnativesampleapp.MainActivity');    

What remains is to actually login into the app using biometrics:

For more info you can check here:

https://github.com/gromanas/ReactNativeSampleApp/blob/master/README.md