Gradle task to run acceptance tests with custom runner

Question

In my project, I have acceptance tests that need a custom instrumentation test runner other than AndroidJUnitRunner and Espresso tests which only run with the AndroidJUnitRunner. I solved this problem by dynamically setting the correct testInstrumentationRunner:

android {
  ...
  defaultConfig {
    ...
    testInstrumentationRunner: getInstrumentation()
  }
}

def getInstrumentation() {
  project.hasProperty('cucumber') ?
        'com.example.test.CucumberTestRunner' :
        'android.support.test.runner.AndroidJUnitRunner'
}

To run my acceptance tests, I need to run ./gradlew connectedCheck -Pcucumber from the command line. But instead of manually typing this every time I want to run these tests, I would like to have a gradle task that does the job for me. The idea was to define the property within the task so that it would be set during the configuration phase and then execute connectedCheck.

task runAcceptanceTests() {
  description = 'Run acceptance tests'
  group = 'acceptanceTests'

  project.ext {
    cucumber = 'cucumber'
  }

  dependsOn connectedCheck
}

However, getInstrumentation() is called before the property is even set within the task. Manually setting the testInstrumentationRunner like this also doesn't work:

android {
  ...
  defaultConfig {
    ...
    testInstrumentationRunner: 'android.support.test.runner.AndroidJUnitRunner'
  }
}

task runAcceptanceTests() {
  description = 'Run acceptance tests'
  group = 'acceptanceTests'

  project.android.defaultConfig.testInstrumentationRunner = 'com.example.test.CucumberTestRunner'

  dependsOn connectedCheck
}

Android then uses the CucumberTestRunner for all instrumentation tests (like Espresso) instead of the AndroidJUnitRunner even if I don't run them using my gradle task.

I also tried something along the line of

task runAcceptanceTests(type: Exec) {
  ...
  commandLine 'connectedCheck', '-Pcucumber'
}

but that doesn't seem to be possible. I found out later that it is not recommended to run tasks from another task anyway.

I guess, the difficulty in my case is that I don't want to have to add any flags when running the gradle task like gradle runAcceptanceTests -Pcucumber. I basically want to be able to run gradle runAcceptanceTests and have it do its thing. Is there a way to do something like this?