Test Retry Rule

Retry.kt

@Retention(AnnotationRetention.RUNTIME)
annotation class Retry(
    val retryCount: Int = -1
)

RetryRule.kt

import org.junit.rules.MethodRule
import org.junit.runners.model.FrameworkMethod
import org.junit.runners.model.Statement

class RetryRule : MethodRule {
    override fun apply(base: Statement, method: FrameworkMethod, target: Any): Statement {
        return object : Statement() {
            override fun evaluate() {
                try {
                    base.evaluate()
                } catch (t: Throwable) {
                    val retry = method.getAnnotation(Retry::class.java)
                    if (retry != null) {
                        if (retry.retryCount > 0) {
                            var throwable = Throwable("Number of max retries reached: $retry.retryCount")
                            for (i in 0 until retry.retryCount) {
                                try {
                                    base.evaluate()
                                    return
                                } catch (t: Throwable) {
                                    throwable = t
                                }
                            }
                            throw throwable
                        } else {
                            base.evaluate()
                        }
                    } else {
                        throw t
                    }
                }
            }
        }
    }
}

RetryRuleTest.kt

import org.junit.Assert.assertEquals
import org.junit.Rule
import org.junit.Test

class RetryRuleTest {
    @get:Rule var rule = RetryRule()
    private var countForever = 0
    private var countMax = 0
    private var countMaxExceeded = 0
    private var countFail = 0

    @Test
    @Retry
    fun itRetriesUntilPasses() {
        countForever++
        assertEquals(2, countForever)
    }

    @Test
    @Retry(4)
    fun itRetriesUntilMaxRetriesExactly() {
        countMax++
        assertEquals(5, countMax)
    }

    @Test
    @Retry(10)
    fun itRetriesUntilMaxRetriesExceeded() {
        countMaxExceeded++
        assertEquals(5, countMaxExceeded)
    }

    @Test
    @Retry(5)
    fun itRetriesUntilMaxRetriesButTestStillFails() {
        try {
            countFail++
            throw Exception("Fail the test")
        } catch (e: Exception) {
            assertEquals("Fail the test", e.message)
            assertEquals(6, countFail)
        }
    }
}