TestingInternalDetails.kt

// The condition here is that the private method is made public or package-private using the `VisibleForTesting` annotation.
@Test
fun `is referral valid with new referral expected value is true`() {
   val friendReferral = getInstance()
   asserTrue(friendReferral.isReferralValid(…))
}

// The condition here is that the private method is made public or package-private using the `VisibleForTesting` annotation.
@Test
fun `process referral valid with new referral verify referral successful`() {
   val friendReferral = getInstance()
   friendReferral.processReferral("testUserId")
   assertThat(referralList.contains("testUserId")).isTrue()
}