Combining Hamkrest and Result4K

problematic.kt

import com.natpryce.Failure
import com.natpryce.Result
import com.natpryce.Success
import com.natpryce.hamkrest.MatchResult
import com.natpryce.hamkrest.Matcher
import com.natpryce.hamkrest.assertion.assertThat
import com.natpryce.hamkrest.equalTo


fun <T, E> assertSuccessThat(actual: Result<T, E>, valueMatcher: Matcher<T>) {
    assertThat(
        actual,
        isSuccessMatching(valueMatcher))
}

fun <T, E> isSuccessOf(expectedValue: T) = isSuccessMatching<T, E>(equalTo(expectedValue))

fun <T, E> isSuccessMatching(valueMatcher: Matcher<T>) : Matcher<Result<T, E>> = object: Matcher<Result<T, E>> {

    override fun invoke(actual: Result<T, E>) = when (actual) {
        is Success -> valueMatcher(actual.value)
        is Failure -> MatchResult.Mismatch("was Failure[${actual.reason}]")
    }

    override val description get() = valueMatcher.description
}
fun <T, E> isFailureWithReason(expectedReason: E): Matcher<Result<T, E>> = isFailureMatching(equalTo(expectedReason))

fun <T, E> isFailureMatching(errorMatcher: Matcher<E>) : Matcher<Result<T, E>> = object: Matcher<Result<T, E>> {

    override fun invoke(actual: Result<T, E>) = when (actual) {
        is Success -> MatchResult.Mismatch("was Success (and should have been Failure)")
        is Failure -> errorMatcher(actual.reason)
    }

    override val description get() = errorMatcher.description
}