Load All Build Variants into test module Android

I have a test module for my app which loads my app content as a dependency and runs robolectric tests. The problem I’m having is that I have many flavours and i want to test them all but with my current setup i can only test one. The build.gradle file for my test module is below.

evaluationDependsOn(":app")
  apply plugin: 'java'
  dependencies {
      def androidModule = project(':app')
    testCompile project(path: ':app', configuration: 'debugCompile')
      def debugVariant = androidModule.android.applicationVariants.all({it.name == 'flavor1_demoDebug'})
    testCompile debugVariant.javaCompile.classpath
    testCompile debugVariant.javaCompile.outputs.files
    testCompile files(androidModule.plugins.findPlugin("com.android.application").getBootClasspath())
      compile 'junit:junit:4.11'
    compile 'org.robolectric:robolectric:2.4'
  }

Does anyone know how I might load in all my build variants so as to test all of them?

Thanks in advance!