Screenshot tests (#130)

* #9 Add snapshot testing library

* #9 Create script to boot test simulators

* #9 Create the UI test plan

* #9 Create shared schemes for test targets

* #9 Disable split view for UI tests

* #9 Fix fastlane dependencies

* #9 Add snapshot testing to the application

* #9 assert screenshots

* #9 fix swipe gestures on iPad

* #9 Fix accessing items in session verification screen

* #9 Workaround for flaky unit test

* #9 Specify scheme for alpha build

* #9 Add reference screenshots

* Update python script path and check assets for png check

* Update script path

* Use static timezone for simulator time

* Fix build after SwiftFormat

* Add changelog

* Upload failed screenshots artifact

* Always upload artifacts

* Update boot simulator script

* Update simulator overridden time

* Install pytz before tests

* Get time from Ruby script

* Disable SwiftUI animation when running UI tests

* Update screenshots after animation setting

* Include reference images in the artifact

* Update matching precision

* Update image matching precision & revert artifact content

* Include Xcode result in the artifact

* Update test output directory

* Disable gradient on splash screen for tests

* Tap next button explicitly

* Wait a bit before checking alert

* Wait 1 second

* Run SwiftFormat on project

* Ignore temporary screenshots

* Fix most of the PR remarks

* Fix conflicts

* Bump Python version to 3

* Update reference screenshots for authentication screens

* Update SwiftFormat

* Fix flakey session verification test.

* Update scheme.

Co-authored-by: Doug <douglase@element.io>

UITests/Sources/Application.swift

@@ -14,12 +14,14 @@
 // limitations under the License.
 //
 
+import SnapshotTesting
 import XCTest
 
 struct Application {
     static func launch() -> XCUIApplication {
         let app = XCUIApplication()
         app.launchEnvironment = ["IS_RUNNING_UI_TESTS": "1"]
+        Bundle.elementFallbackLanguage = "en"
         app.launch()
         return app
     }
@@ -36,4 +38,39 @@ extension XCUIApplication {
         
         button.tap()
     }
+
+    /// Assert screenshot for a screen with the given identifier. Does not fail if a screenshot is newly created.
+    /// - Parameter identifier: Identifier of the UI test screen
+    func assertScreenshot(_ identifier: UITestScreenIdentifier) {
+        let failure = verifySnapshot(matching: screenshot().image,
+                                     as: .image(precision: 0.98, scale: nil),
+                                     named: identifier.rawValue,
+                                     testName: testName)
+
+        if let failure = failure,
+           !failure.contains("No reference was found on disk."),
+           !failure.contains("to test against the newly-recorded snapshot") {
+            XCTFail(failure)
+        }
+    }
+
+    private var testName: String {
+        osVersion + "-" + languageCode + "-" + regionCode + "-" + deviceName
+    }
+
+    private var deviceName: String {
+        UIDevice.current.name
+    }
+
+    private var languageCode: String {
+        Locale.current.languageCode ?? ""
+    }
+
+    private var regionCode: String {
+        Locale.current.regionCode ?? ""
+    }
+
+    private var osVersion: String {
+        UIDevice.current.systemVersion.replacingOccurrences(of: ".", with: "-")
+    }
 }