Firely is an A/B Testing overlay based on Firebase Remote Config. It's a work in progress to simplify the integration and make the management of A/B testing XPs safer.

compile 'com.firely:core:1.0.0'

You need to apply the plugin (TODO integrate in maven repo):

buildscript {
    repositories {
        mavenLocal()
        jcenter()
    }

    dependencies {
        classpath group: 'com.busbud.android', name: 'firely-plugin', version: '0.1.0'
    }
}

apply plugin: 'com.busbud.android.firely'

You also need to import the aar (TODO integrate in maven repo):

compile project(':firely-0.1.0')

This library, integrated in your gradle project, only requires:

• A firely-config.json file that will contains the type of items, the keys, and the default value
• A call to Firely.setup(Context context) from the Application.onCreate() method
• One proguard rule

firely-config.json file is organized in 3 main sections (for us, but it can have the "names" you want):

• Feature Flags
• Config
• Experiments (or A/B Tests)

Here is an example of firely-config.json:

{
  "config": [
    {
      "key": "android_version_code_min",
      "default": 0
    }
  ],
  "feature_flag": [
    {
      "key": "refer_a_friend",
      "default": true
    },
    {
      "key": "promotion_url",
      "default": ""
    }
  ],
  "experiment": [
    {
      "key": "xp_button_pay",
      "default": "control"
    }
  ]
}

Firely is an Android library that come with a gradle plugin, firely-plugin. It will generate a FirelyConfig.java file based on the firely-config.json, like the R.java android creates. The FirelyConfig.java will contain Enums that match the configuration. You can then use these enums on Firely to get LiveVariable, CodeBlock, OrderedArrayBlock.

Let's imagine I am using Remote Config to restrict my user to a minimum Android version on which they can run (otherwise they have to update the app). With Firely, I can instantiate a LiveVariable that will use this setting:

LiveVariable<Integer> minAndroidRemoteVersion = Firely.integerVariable(FirelyConfig.Config.ANDROID_VERSION_CODE_MIN);

FirelyConfig.Config.ANDROID_VERSION_CODE_MIN is generated by the plugin and the default value is 0.

Now, anytime I need to get the last version that has been fetched, I just call:

Integer lastVersion = minAndroidRemoteVersion.get();

Here is another example with a feature flag:

if (Firely.booleanVariable(FirelyConfig.FeatureFlag.REFER_A_FRIEND).get()) {
	// Add the view
}

Now I need to build out an XP that will change the text of a button.

Firely.codeBlock(Remote.Experiment.XP_BUTTON)
	.withVariant("billed_currency", "no_price")
	.execute(
	() -> advance.setText(getString(R.string.bb_payment_cta)), // control
	() -> advance.setText(.getString(R.string.bb_payment_cta_2)), // billed_currency
	() -> advance.setText(getString(R.string.bb_payment_cta_3))); // no_price

NOTE: we are always using "control" as the default value and as the control group for A/B Tests.

In the Busbud Android App, we use a lot of blocks and lists. Let's imagine you have N blocks of data in a page. You want to A/B test which one should go first and the order for all the others. A basic approach could be to have N! variants.

If we have three items: 1-2-3, 2-1-3, 2-3-1, 1-3-2, 3-2-1, 3-1-2

And while using CodeBlocks:

Firely.codeBlock(Remote.Experiment.XP_BUTTON)
	.withVariant("2-1-3", "2-3-1", "1-3-2", "3-2-1", "3-1-2")
	.execute(
	() -> {
		addOne();
		addTwo();
		addThree();
	}, // control
	() -> {
		addTwo();
		addOne();
		addThree();
	},
	... etc

Really inefficient.

Another approach is to use OrderedArrayBlock. You will use one Firebase entry:

{
  ...
  "experiment": [
    {
      "key": "xp_mypage_order",
      "default": "one,two,three"
    }
  ]
}

OrderedArrayBlock mCheckoutXp = 
		Firely.orderedArrayBlock(FirelyConfig.Experiment.XP_CHECKOUT_ORDER)
			.addStep("one", () -> addOne())
			.addStep("two", () -> addTwo())
			.addStep("three", () -> addThree());

And you can control your A/B Tests from the Firebase Remote Config dashboard by changing the xp_mypage_order key.

three,one,two will then call addThree(), addOne(), addTwo(). You can use this to remotely control the order of lists.

One of the highlights of Firebase is that everything is working together. In the documentation, Firebase proposes putting the values, manually, as a User Property:

String experiment1_variant = FirebaseRemoteConfig.getInstance().getString("experiment1");
   AppMeasurement.getInstance(context).setUserProperty("MyExperiment",experiment1_variant);

That's nice, but it does not fit our needs. Putting the property at the user level means it will be erased over time and we will lose the information. Instead, we prefer to tag all the events with all the experiments that have been applied at the time the event is triggered.

We added a method on Firely to help with this:

Firely.getAllPropsWithCurrentValue()

And this method is called each time we send an event and merged into the property list. Therefore we can track the configuration changes over time.

You can build locally the project by:

1. Building the plugin:

./gradlew :firely-plugin:publishToMaven -c plugin.gradle

2. Create a firebase project for com.busbud.android.firely.sample and copy the google-service.json in the /firely-sample repository

3. Build the project: ./gradlew assembleDebug