Creating an Espresso Matcher for a class with generics

Issue

I'm trying to create a new Matcher for espresso in order to be able to select a list item. This works fine for a simple class like Office. See this example.

  private fun withOffice(title: String): Matcher<Any> {
    return object : BoundedMatcher<Any, Office>(Office::class.java) {
        override fun describeTo(description: Description?) {
            description?.appendText("with title '$title'");
        }

        public override fun matchesSafely(office: Office): Boolean {
            return office.name == title
        }
    }
}

However things get more difficult when bringing in generics, like in this class.

class KeyTranslationPair<F, S> extends Pair<F, S>

Trying to create a Matcher like this

  private fun withCompanyType(companyType: CompanyType): Matcher<Any> {
    return object : BoundedMatcher<Any, KeyTranslationPair<CompanyType, String>>(KeyTranslationPair<CompanyType, String>::class.java) {
        override fun describeTo(description: Description?) {
            description?.appendText("with companyType '$companyType'");
        }

        public override fun matchesSafely(keyTranslationPair: KeyTranslationPair<CompanyType, String>): Boolean {
            return keyTranslationPair.key == companyType
        }
    }
}

results in the following error

My assumption is that kotlin get things mixed up with the java type system. Maybe someone has an idea here.

Solution

That's because KeyTranslationPair<CompanyType,Strnig> is not a class, when is saying class means KeyTranslationPair::class.java, so, you can do it like :

return object : BoundedMatcher<Any, KeyTranslationPair<*,*>>(KeyTranslationPair::class.java)

And you are saying that you don't know what's inside of the KeyTranslationPair, and since it's a Generic you'll have to change the matchesSafely to :

override fun matchesSafely(item: KeyTranslationPair<*, *>?): Boolean {
   return item?.key == companyType
}

And also you can check if Key is an instance of CompanyType doing :

override fun matchesSafely(item: KeyTranslationPair<*, *>?): Boolean {
    if(item?.key is CompanyType){
        return item.key == companyType
    }
        return false
    }

Hope it helps.

Answered By - Skizo-ozᴉʞS