adding first set of tests: refactoring

Kotlin/src/test/kotlin/com/gildedrose/GildedRoseBaseTest.kt

@@ -36,7 +36,7 @@ abstract class GildedRoseBaseTest {
         testGildedRose(name, initialSellIn, initialQuality, numberDays, resultingSellIn, resultingQuality)
     }
 
-    fun testGildedRose(
+    private fun testGildedRose(
         name: String,
         initialSellIn: Int,
         initialQuality: Int,
@@ -48,7 +48,7 @@ abstract class GildedRoseBaseTest {
         val items = arrayOf(item)
         val app = GildedRose(items)
 
-        (1..numberDays).forEach() {
+        (1..numberDays).forEach { _ ->
             app.updateQuality()
         }
         Assertions.assertThat(item.name).isEqualTo(name)
@@ -56,7 +56,7 @@ abstract class GildedRoseBaseTest {
         Assertions.assertThat(item.quality).isEqualTo(resultingQuality)
     }
 
-    fun combinationsSource(): Stream<Arguments> = Stream.of(*combinationsToTest)
+    private fun combinationsSource(): Stream<Arguments> = Stream.of(*combinationsToTest)
 
 
 }

Kotlin/src/test/kotlin/com/gildedrose/GildedRoseSulfurasTest.kt

@@ -1,10 +1,7 @@
 package com.gildedrose
 
 import org.junit.jupiter.api.TestInstance
-import org.junit.jupiter.params.ParameterizedTest
 import org.junit.jupiter.params.provider.Arguments
-import org.junit.jupiter.params.provider.MethodSource
-import java.util.stream.Stream
 
 @TestInstance(TestInstance.Lifecycle.PER_CLASS)
 internal class GildedRoseSulfurasTest : GildedRoseBaseTest(){

Kotlin/src/test/kotlin/com/gildedrose/RandomizedRegressionTest.kt

@@ -1,70 +1,75 @@
 package com.gildedrose
 
 import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
 import kotlin.random.Random
 
-/*
-TODO:
- - const voor maxNrDays, MaxNrItems, MaxInitialQuality, MaxInitialQuality
- - run als unit test, draai 1 minuut, of 1.000.000 keer
- - comment: deze kan flaky zijn, maar bij 1.000.000 is die kans wel erg klein
-
- */
-
-val productLists = listOf(
+private const val NR_TESTS_TO_RUN = 100_000 // 100.000 random tests should be enough to cover any untested cases by the normal unit tests
+private const val MAX_NR_ITEMS = 5
+private const val MAX_NR_DAYS = 100
+private const val MAX_INITIAL_QUALITY = 100
+private const val MIN_INITIAL_SELLIN = -10
+private const val MAX_INITIAL_SELLIN = 100
+private val PRODUCTS_LIST = listOf(
     "Aged Brie",
     "Sulfuras, Hand of Ragnaros",
     "Backstage passes to a TAFKAL80ETC concert",
     "Foo"
 )
+private val random = Random(System.currentTimeMillis())
 
-val random = Random(System.currentTimeMillis())
+class RandomizedRegressionTest {
+    @Test
+    fun `test random combinations and compare the result from the legacy code with the refactored code`() {
+        (0..NR_TESTS_TO_RUN).forEach{
+            // create new random combination of items
+            val nrItemsToTest = random.nextInt(1,MAX_NR_ITEMS)
+            val nrDays = random.nextInt(1,MAX_NR_DAYS)
+            val initialItems = createRandomItemList(nrItemsToTest)
+            val legacyItems = initialItems.deepClone()
+            val refacturedItems = legacyItems.deepClone()
 
+            // clone the items for the legacy and the refactored implementation
+            val legacyApp = GildedRoseLegacy(legacyItems)
+            val refactoredApp = GildedRose(refacturedItems)
 
-fun main(args: Array<String>) {
-    (0..Int.MAX_VALUE).forEach(){
-        val nrItemsToTest = random.nextInt(1,5)
-        val nrDays = random.nextInt(1,100)
-        val initialItems = createRandomItemList(nrItemsToTest)
-        val legacyItems = initialItems.deepClone()
-        val refacturedItems = legacyItems.deepClone()
+            // update the quality for a number of days for both the legacy and the refactored implementation
+            println("testing round $it, with $nrItemsToTest items and $nrDays days")
+            (1..nrDays).forEach { _ ->
+                legacyApp.updateQuality()
+                refactoredApp.updateQuality()
+            }
 
-        val legacyApp = GildedRoseLegacy(legacyItems)
-        val refactoredApp = GildedRose(refacturedItems)
-
-        println("testing round $it, with $nrItemsToTest items and $nrDays days")
-        (1..nrDays).forEach {
-            legacyApp.updateQuality()
-            refactoredApp.updateQuality()
+            // compare the result of the legacy and the refactored implementation
+            val testDescription : String = describeTestcase(initialItems, nrDays, refactoredApp.items, legacyApp.items)
+            val actialItemsAsString = describeItems(refactoredApp.items)
+            val expectedItemsAsString = describeItems(legacyApp.items)
+            assertThat(actialItemsAsString).`as`("The following testcase failed: \n$testDescription").isEqualTo(expectedItemsAsString)
         }
-
-        val testDescription : String = describeTestcase(initialItems, nrDays, refactoredApp.items, legacyApp.items)
-        val actialItemsAsString = describeItems(refactoredApp.items)
-        val expectedItemsAsString = describeItems(legacyApp.items)
-        assertThat(actialItemsAsString).`as`("The following testcase failed: \n$testDescription").isEqualTo(expectedItemsAsString)
     }
+
+    private fun describeTestcase(initialItems: Array<Item>, nrDays: Int, actualItems: Array<Item>, expectedItems: Array<Item>) =
+        "Initial items: \n${describeItems(initialItems)}\n\n"+
+                "expected items after $nrDays days:\n"+
+                "${describeItems(expectedItems)}\n\n"+
+                "actual items after $nrDays days:\n"+
+                describeItems(actualItems)
+
+    private fun describeItems(items: Array<Item>) = items.joinToString("\n") { " -${it.name}: sellIn:${it.sellIn} quality:${it.quality}" }
+
+    private fun createRandomItem(): Item{
+        val nameIndex = random.nextInt(PRODUCTS_LIST.size)
+        val name = PRODUCTS_LIST[nameIndex]
+        val sellIn =random.nextInt(MIN_INITIAL_SELLIN, MAX_INITIAL_SELLIN)
+        val quality = random.nextInt(MAX_INITIAL_QUALITY)
+        return Item(name,sellIn,quality)
+    }
+
+    private fun Item.clone() = Item(name,sellIn,quality)
+
+    private fun Array<Item>.deepClone() = map { it.clone() } .toTypedArray()
+
+    private fun createRandomItemList(count: Int) = (0..count).map { createRandomItem() }.toTypedArray()
+
+
 }
-
-fun describeTestcase(initialItems: Array<Item>, nrDays: Int, actualItems: Array<Item>, expectedItems: Array<Item>) =
-    "Initial items: \n${describeItems(initialItems)}\n\n"+
-    "expected items after $nrDays days:\n"+
-    "${describeItems(expectedItems)}\n\n"+
-    "actual items after $nrDays days:\n"+
-    describeItems(actualItems)
-
-fun describeItems(items: Array<Item>) = items.map { " -${it.name}: sellIn:${it.sellIn} quality:${it.quality}" }.joinToString("\n")
-
-private fun createRandomItem(): Item{
-    val nameIndex = random.nextInt(productLists.size)
-    val name = productLists[nameIndex]
-    val sellIn =random.nextInt(-10, 100)
-    val quality = random.nextInt(100)
-    return Item(name,sellIn,quality)
-}
-
-private fun Item.clone() = Item(name,sellIn,quality)
-
-private fun Array<Item>.deepClone() = map { it.clone() } .toTypedArray()
-
-
-private fun createRandomItemList(count: Int) = (0..count).map { createRandomItem() }.toTypedArray()