Added advanced rules

swift/Tests/GildedRoseTests/AdvancedRules.swift

@@ -0,0 +1,97 @@
+//
+//  AdvancedRules.swift
+//  GildedRose
+//
+//  Created by Lucas van Dongen on 23/11/2020.
+//
+
+@testable import GildedRose
+import XCTest
+
+class AdvancedRules: XCTestCase {
+    private let expiringItem = Item(name: "Expiring Item", sellIn: 1, quality: 5)
+    private let noQualityItem = Item(name: "No quality Item", sellIn: 1, quality: 0)
+    private let brieItem = Item(name: "Aged Brie", sellIn: 2, quality: 0)
+    private let veryGoodBrieItem = Item(name: "Aged Brie", sellIn: 2, quality: 50)
+    private let sulfuras = Item(name: "Sulfuras, Hand of Ragnaros", sellIn: 0, quality: 50)
+
+    //- Once the sell by date has passed, Quality degrades twice as fast
+    func testQualityDegradationAfterExpire() {
+        let initialQuality = expiringItem.quality
+
+        let system = GildedRose(items: [expiringItem])
+        system.updateQuality()
+
+        let qualityAfterUpdateNotExpiredYet = system.items.first!.quality
+        let qualityLossNotExpired = initialQuality - qualityAfterUpdateNotExpiredYet
+
+        system.updateQuality()
+
+        let qualityAfterUpdateExpired = system.items.first!.quality
+        let qualityLossExpired = qualityAfterUpdateNotExpiredYet - qualityAfterUpdateExpired
+
+        XCTAssertEqual(qualityLossNotExpired * 2, qualityLossExpired)
+    }
+
+    //- The Quality of an item is never negative
+    func testQualityNeverNegative() {
+        let system = GildedRose(items: [noQualityItem])
+        system.updateQuality()
+
+        let qualityAfterUpdate = system.items.first!.quality
+
+        XCTAssertEqual(0, noQualityItem.quality)
+        XCTAssertEqual(0, qualityAfterUpdate)
+    }
+
+    //- "Aged Brie" actually increases in Quality the older it gets
+    func testBrieIncreasesInQuality() {
+        let initialQuality = brieItem.quality
+        let system = GildedRose(items: [brieItem])
+        system.updateQuality()
+        XCTAssertGreaterThan(system.items.first!.quality, initialQuality)
+    }
+
+    //- The Quality of an item is never more than 50
+    func testQualityNeverOverMaximum() {
+        let initialQuality = veryGoodBrieItem.quality
+        let system = GildedRose(items: [veryGoodBrieItem])
+        system.updateQuality()
+        XCTAssertEqual(initialQuality, 50)
+        XCTAssertEqual(system.items.first!.quality, 50)
+    }
+    
+    //- "Sulfuras", being a legendary item, never has to be sold, never decreases in Quality
+    func testLegendaryNoExpire() {
+        let initialSellIn = sulfuras.sellIn
+        let initialQuality = sulfuras.quality
+
+        let system = GildedRose(items: [sulfuras])
+        system.updateQuality()
+
+        XCTAssertEqual(initialSellIn, system.items.first!.sellIn)
+        XCTAssertEqual(initialQuality, system.items.first!.quality)
+    }
+
+    //- "Backstage passes", like aged brie, increases in Quality as its SellIn value approaches;
+    //  Quality increases by 2 when there are 10 days or less and by 3 when there are 5 days or less but
+    //  Quality drops to 0 after the concert
+    func testBackstagePasses() {
+        let backstagePassMoreThan10Days = Item(name: "Backstage passes to a TAFKAL80ETC concert", sellIn: 15, quality: 20)
+        let backstagePassLessThan10Days = Item(name: "Backstage passes to a TAFKAL80ETC concert", sellIn: 10, quality: 20)
+        let backstagePassLessThan5Days = Item(name: "Backstage passes to a TAFKAL80ETC concert", sellIn: 5, quality: 20)
+        let backstagePassExpired = Item(name: "Backstage passes to a TAFKAL80ETC concert", sellIn: 0, quality: 20)
+
+        XCTAssertTrue(hasExpectedQuality(item: backstagePassMoreThan10Days, quality: 21))
+        XCTAssertTrue(hasExpectedQuality(item: backstagePassLessThan10Days, quality: 22))
+        XCTAssertTrue(hasExpectedQuality(item: backstagePassLessThan5Days, quality: 23))
+        XCTAssertTrue(hasExpectedQuality(item: backstagePassExpired, quality: 0))
+    }
+
+    private func hasExpectedQuality(item: Item, quality: Int) -> Bool {
+        let system = GildedRose(items: [item])
+        system.updateQuality()
+
+        return item.quality == quality
+    }
+}