<h1>How to automate build and testing in Flutter with Gitlab</h1>
Let&#39;s use Docker image by <a href="https://github.com/PlugFox/docker_flutter">Plugfox</a>, which is targeting Flutter and comes with all dependencies required, such as Android SDK, JVM and so on. 
In this example, we&#39;ll be using free tier of Gitlab, and in order to minify the load on the flow, we&#39;ll define the GIT_DEPTH variable, which should speed up the 
cloning of repository alongside other environment variables, which are required during the building of <a href="https://developer.android.com/guide/app-bundle">APK/AppBundle</a>.
<h2>Prerequisites for this pipeline</h2>
<ol>
<li>Have a <a href="https://developer.android.com/studio/publish/app-signing#generate-key">android keystore</a> file. You can quickly generate it using following command:</li>
</ol>
<pre><code class="hljs language-bash">keytool -genkey -v -keystore example.keystore -alias alias_name -keyalg RSA -keysize 2048 -validity 10000
</code></pre><ol start="2">
<li>Setup your <a href="https://docs.gitlab.com/ee/ci/secure_files/">Gitlab secure files</a>.
</li>
<li>Prepare integration test, for example
</li>
</ol>
<pre><code class="hljs language-dart">import &#x27;package:flutter_test/flutter_test.dart&#x27;;
import &#x27;package:integration_test/integration_test.dart&#x27;;

void main() {
 IntegrationTestWidgetsFlutterBinding.ensureInitialized();

 group(&#x27;example test&#x27;, () {
 testWidgets(&#x27;dummy test&#x27;, (tester) async {
 expect(10, greaterThanOrEqualTo(2));
 });
 });
}
</code></pre><h2>Building release appbundle</h2>
In order to build the Flutter application, we will use the keystore, which you configured at the prerequisite 1 and upload it to 
the Gitlab secure files. In order to download secure files, Gitlab requires to execute shell script, let&#39;s run it: 
<pre><code class="hljs language-bash">curl --silent &quot;https://gitlab.com/gitlab-org/incubation-engineering/mobile-devops/download-secure-files/-/raw/main/installer&quot; | bash
</code></pre>Now, let&#39;s configure the signing process. In order to do so, we will use key.properties file. Make sure, that your build.gradle inside flutter 
application. Check the <code>android/app/build.gradle</code> file, and make sure it has something like this:
<pre><code class="hljs language-gradle">def keystoreProperties = new Properties()
def keystorePropertiesFile = rootProject.file(&#x27;key.properties&#x27;)
if (keystorePropertiesFile.exists()) {
 keystoreProperties.load(new FileInputStream(keystorePropertiesFile))
}

android {
 // rest of configuration...

 signingConfigs {
 release {
 keyAlias keystoreProperties[&#x27;keyAlias&#x27;]
 keyPassword keystoreProperties[&#x27;keyPassword&#x27;]
 storeFile keystoreProperties[&#x27;storeFile&#x27;] ? file(keystoreProperties[&#x27;storeFile&#x27;]) : null
 storePassword keystoreProperties[&#x27;storePassword&#x27;]
 }
 }
}
</code></pre>Now, let&#39;s prepopulate the key.properties file with necessary details for signing to work
<pre><code class="hljs language-bash">echo &quot;storeFile=$(pwd)/key.keystore&quot; &gt; android/key.properties
echo &quot;storePassword=$KEYSTORE_PASSWORD&quot; &gt;&gt; android/key.properties
echo &quot;keyAlias=$ALIAS&quot; &gt;&gt; android/key.properties ## Testing Flutter application in CI system
echo &quot;keyPassword=$KEY_PASSWORD&quot; &gt;&gt; android/key.properties
</code></pre>Finally, you can execute building command like this:
<pre><code class="hljs language-bash">flutter build appbundle --no-pub --obfuscate --split-debug-info=debug-info-appbundle # if you need appbundle format
flutter build apk --no-pub --obfuscate --split-debug-info=debug-info-apk # if you need apk
</code></pre><h2>Implementing CI testing in Flutter</h2>
In order to test, make sure that your Android device is visible with the <code>adb devices</code> command. The following steps assume that you have followed this step. 
Optional 
If you would like to precache the Android SDK, you can use following command for extracting the <code>compileSdk</code> value and pass it to sdkmanager for installation
<pre><code class="hljs language-bash">cat android/app/build.gradle | grep compileSdk | tr -d -c 0-9 | /opt/android/cmdline-tools/latest/bin/sdkmanager &quot;platforms;android-$(cat -)&quot;
</code></pre>Usually, tests assume that your screen is unlocked, so we can schedule unlocking of your screen beforehands by inputting following command:
<pre><code class="hljs language-bash">adb shell input keyevent 26 &amp;&amp; adb shell input touchscreen swipe 930 880 930 380
</code></pre>Optional 
If you want to have the screen opened upon installation of your application, you can modify your <code>MainActivity.kt</code> with the following changes: 
<pre><code class="hljs language-kotlin">override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState);
 if (BuildConfig.DEBUG) { // we don&#x27;t want to have this behavior on release builds, so keep it only to tests
 val keyguardManager = getSystemService(Context.KEYGUARD_SERVICE) as KeyguardManager;
 if (Build.VERSION.SDK_INT &gt;= Build.VERSION_CODES.P) {
 setShowWhenLocked(true)
 setTurnScreenOn(true)
 keyguardManager.requestDismissKeyguard(this, null)
 } else {
 // For older versions of Android, you can use the deprecated method as a fallback
 keyguardLock?.disableKeyguard()
 window.addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON or WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
 }
 }
}
</code></pre>We also were having timeouts while connecting to the device and Flutter VM. We solved it using following command: 
<pre><code class="hljs language-bash">sed -i &#x27;/).timeout(/,/);/{ s/).timeout.*/);/; t; d;}&#x27; /opt/flutter/packages/flutter_tools/lib/src/test/integration_test_device.dart
</code></pre>Finally, execute <code>flutter test path/to/your_test.dart</code> and you&#39;re ready to go!
<h2>Complete .gitlab-ci.yml</h2>
Here&#39;s the complete .gitlab-ci.yml for building and testing of Flutter applications
<pre><code class="hljs language-yaml">image: plugfox/flutter:3.10.6-android

variables:
 GIT_DEPTH: &quot;1&quot;
 KEYSTORE_PASSWORD: your_keystore_password
 ALIAS: your_alias
 KEY_PASSWORD: your_key_password

stages:
 - build
 - test
 - deploy

e2e_test:
 stage: test 
 interruptible: true
 only:
 - merge_requests
 script: 
 - flutter pub get
 - flutter precache --no-web
 - cat android/app/build.gradle | grep compileSdk | tr -d -c 0-9 | /opt/android/cmdline-tools/latest/bin/sdkmanager &quot;platforms;android-$(cat -)&quot;
 - flutter build apk --no-pub --debug
 - adb shell input keyevent 26 &amp;&amp; adb shell input touchscreen swipe 930 880 930 380
 - sed -i &#x27;/).timeout(/,/);/{ s/).timeout.*/);/; t; d;}&#x27; /opt/flutter/packages/flutter_tools/lib/src/test/integration_test_device.dart
 - flutter test integration_test/app_test.dart

build_flutter_bundle:
 stage: build
 timeout: 2 hours
 variables:
 SECURE_FILES_DOWNLOAD_PATH: &#x27;./&#x27;
 script:
 - curl --silent &quot;https://gitlab.com/gitlab-org/incubation-engineering/mobile-devops/download-secure-files/-/raw/main/installer&quot; | bash
 - echo &quot;storeFile=$(pwd)/key.keystore&quot; &gt; android/key.properties
 - echo &quot;storePassword=$KEYSTORE_PASSWORD&quot; &gt;&gt; android/key.properties
 - echo &quot;keyAlias=$ALIAS&quot; &gt;&gt; android/key.properties
 - echo &quot;keyPassword=$KEY_PASSWORD&quot; &gt;&gt; android/key.properties
 - flutter pub get --verbose
 - flutter precache --no-web
 - cat android/app/build.gradle | grep compileSdk | tr -d -c 0-9 | /opt/android/cmdline-tools/latest/bin/sdkmanager &quot;platforms;android-$(cat -)&quot;
 - apk add openjdk17-jre-headless openjdk17-jdk # you should install the java version that your application was written with during CI
 - flutter build appbundle --no-pub --obfuscate --split-debug-info=debug-info-appbundle
 - flutter build apk --no-pub --obfuscate --split-debug-info=debug-info-apk
 - cp build/app/outputs/bundle/app-release.aab ./app-release.aab
 - cp build/app/outputs/flutter-apk/app-release.apk ./amazon-release.apk
 artifacts:
 paths:
 - app-release.aab
 - app-release.apk
 expire_in: 1 week
 rules:
 - if: $CI_COMMIT_BRANCH == &#x27;master&#x27;
 when: manual
 - when: never
</code></pre>Photo by <a href="https://unsplash.com/@toluobde?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText">Tolu Olubode</a> on <a href="https://unsplash.com/photos/PlBsJ5MybGc?utm_source=unsplash&utm_medium=referral&utm_content=creditCopyText">Unsplash</a>