README.md

wisp-feature-testing

Fake implementation of FeatureFlags.

See wisp-feature for more details on feature flags.

Usage - Strongly Typed

Step 1: Define a feature flag as described in wisp-feature

Step 2: Use the feature flag in your code:

For example, you might have a service like this:

class ThingToTest(private val featureFlags: FeatureFlags) {
  fun getInstructions(customerId: String): String {
    val missileButtonEnabled = featureFlags.get(
      MissileButtonShouldBeEnabled(
        customerId = customerId,
        region = Region.Australia,
        cardBin = CardBIN("451213")  
      )  
    )  
      
    return if (missleButtonEnabled) {
      "Press the missile button"  
    } else {
      "Panic!"  
    }
  }  
}

Step 3: Use FakeFeatureFlags to test ThingToTest:

class ThingToTestTests {
  @Test  
  fun `it should tell me to press the button if the missile button is enabled`() {
    val featureFlags = FakeFeatureFlags()
      .override<MissileButtonShouldBeEnabled>(true)
      
    val thing = ThingToTest(featureFlags)  
      
    thing.getInstructions(customerId = "fred").shouldBe("Press the missile button")
  }
    
  @Test  
  fun `it should tell me to panic if the missile button is not enabled`() {
    val featureFlags = FakeFeatureFlags()
      .override<MissileButtonShouldBeEnabled>(false)

    val thing = ThingToTest(featureFlags)

    thing.getInstructions(customerId = "alice").shouldBe("Panic!")
  }
}

Bonus Step: Only match flags for specific fields

Sometimes you want to say "only enable the missile button for Mary". The override function has an optional matcher value that must be true for the override to match.

class ThingToTestTests {
  @Test
  fun `it should tell mary to press the button`() {
    val featureFlags = FakeFeatureFlags()
      .override<MissileButtonShouldBeEnabled>(true) { it.customerId == "mary" }

    val thing = ThingToTest(featureFlags)

    thing.getInstructions(customerId = "mary").shouldBe("Press the missile button")
  }
}

Usage - Legacy

// TODO - usages...