Add tests

Readme.md

@@ -14,8 +14,11 @@ tktk
 
 ## Installation
 
+Honestly you should probably just copy [BetterNotification.swift]() into your project.
+
 The only way to install this package is with Swift Package Manager (SPM). Please [file a new issue][] or submit a pull-request if you want to use something else.
 
+[BetterNotification.swift]: https://github.com/samsonjs/BetterNotification/blob/main/Sources/BetterNotification/BetterNotification.swift
 [file a new issue]: https://github.com/samsonjs/BetterNotification/issues/new
 
 ### Supported Platforms

Sources/BetterNotification/BetterNotification.swift

@@ -24,6 +24,8 @@ public extension BetterNotification {
     static var userInfoKey: String { notificationName.rawValue }
 }
 
+// MARK: -
+
 public extension Notification {
     /// Creates a `Notification` instance for the given `BetterNotification` value.
     ///
@@ -41,7 +43,25 @@ public extension Notification {
             userInfo: [BN.userInfoKey: betterNotification]
         )
     }
+
+    /// Extracts a `BetterNotification` value of the specified type from this `Notification`'s `userInfo`.
+    ///
+    /// - Returns: The extracted `BetterNotification` value when found, otherwise `nil`.
+    func better<BN: BetterNotification>() -> BN? {
+        guard let object = userInfo?[BN.userInfoKey] else {
+            NSLog("[\(BN.self)] Object missing from userInfo[\"\(BN.userInfoKey)\"]")
+            return nil
         }
+        guard let betterNotification = object as? BN else {
+            NSLog("[\(BN.self)] Failed to cast \(object) to \(BN.self)")
+            return nil
+        }
+
+        return betterNotification
+    }
+}
+
+// MARK: -
 
 public extension NotificationCenter {
     /// Returns an `AsyncSequence` of notifications of a specific `BetterNotification` type.
@@ -54,18 +74,18 @@ public extension NotificationCenter {
         for betterType: BN.Type
     ) -> any AsyncSequence<BN, Never> {
         notifications(named: BN.notificationName)
-            .compactMap { $0.userInfo?[BN.userInfoKey] as? BN }
+            .compactMap { $0.better() }
     }
 
-    /// Returns a Combine publisher that emits `BetterNotification` values of a specific type.
+    /// Returns a Combine publisher that emits `BetterNotification` values of the given type.
     ///
     /// - Parameter betterType: The `BetterNotification` type to observe.
     /// - Returns: A publisher emitting `BetterNotification` values.
-    func publisher<T: BetterNotification>(
-        for betterType: T.Type
-    ) -> AnyPublisher<T, Never> {
+    func publisher<BN: BetterNotification>(
+        for betterType: BN.Type
+    ) -> AnyPublisher<BN, Never> {
         publisher(for: betterType.notificationName)
-            .compactMap { $0.userInfo?[T.userInfoKey] as? T }
+            .compactMap { $0.better() }
             .eraseToAnyPublisher()
     }
 }

Tests/BetterNotificationTests/BetterNotificationTests.swift

@@ -1,6 +1,138 @@
-import Testing
 @testable import BetterNotification
+import Combine
+import Foundation
+import Testing
 
-@Test func example() async throws {
-    // Write your test here and use APIs like `#expect(...)` to check expected conditions.
+struct BetterNotificationTests {
+    @Test func notificationName() {
+        #expect(HitchhikersNotification.notificationName.rawValue == "BetterNotification:HitchhikersNotification")
+    }
+
+    @Test func userInfoKey() {
+        #expect(HitchhikersNotification.userInfoKey == "BetterNotification:HitchhikersNotification")
+    }
+
+    // MARK: - Notification extensions
+
+    @Test func buildNotification() {
+        let hitchhikers = HitchhikersNotification(answer: 42)
+        let notification = Notification.better(hitchhikers)
+        #expect(notification.name == HitchhikersNotification.notificationName)
+        #expect(notification.userInfo?.count == 1)
+        let key = HitchhikersNotification.userInfoKey
+        let userInfoValue = notification.userInfo?[key] as? HitchhikersNotification
+        #expect(userInfoValue == hitchhikers)
+    }
+
+    @Test func extractBetterPayload() {
+        let hitchhikers = HitchhikersNotification(answer: 42)
+        let notification = Notification.better(hitchhikers)
+        let extracted: HitchhikersNotification? = notification.better()
+        #expect(extracted == hitchhikers)
+    }
+
+    @Test func extractBetterPayloadFailsOnWrongType() {
+        let imposter = Notification(
+            name: HitchhikersNotification.notificationName,
+            object: nil,
+            userInfo: [HitchhikersNotification.userInfoKey: "imposter"]
+        )
+        let extracted: HitchhikersNotification? = imposter.better()
+        #expect(extracted == nil)
+    }
+
+    @Test func extractBetterPayloadFailsOnMissingPayload() {
+        let wrongNotification = Notification(name: HitchhikersNotification.notificationName)
+        let extracted: HitchhikersNotification? = wrongNotification.better()
+        #expect(extracted == nil)
+    }
+
+    // MARK: NotificationCenter extensions
+
+    // It's important that the tests and the notification-observing tasks are not on the same actor,
+    // so we make the tests @MainActor and observe notifications on another actor. Otherwise it's
+    // a deadlock.
+
+    @Test(.timeLimit(.minutes(1)))
+    @MainActor func notificationCenterAsyncSequence() async throws {
+        let center = NotificationCenter()
+        nonisolated(unsafe) var received = false
+        Task {
+            for await hitchhikers in center.notifications(for: HitchhikersNotification.self) {
+                #expect(hitchhikers.answer == 42)
+                received = true
+                break
+            }
+        }
+        await Task.yield()
+
+        let hitchhikers = HitchhikersNotification(answer: 42)
+        center.post(.better(hitchhikers))
+        while !received { await Task.yield() }
+    }
+
+    @Test(.timeLimit(.minutes(1)))
+    @MainActor func notificationCenterAsyncSequenceIgnoresInvalidPayloads() async throws {
+        let center = NotificationCenter()
+        nonisolated(unsafe) var received = false
+        let task = Task {
+            for await _ in center.notifications(for: HitchhikersNotification.self) {
+                received = true
+            }
+        }
+        defer { task.cancel() }
+        await Task.yield()
+
+        // Post an invalid one that should be ignored.
+        let imposter = Notification(
+            name: HitchhikersNotification.notificationName,
+            object: nil,
+            userInfo: [HitchhikersNotification.userInfoKey: "imposter"]
+        )
+        center.post(imposter)
+
+        try await Task.sleep(for: .milliseconds(10))
+        #expect(!received)
+    }
+
+    @Test(.timeLimit(.minutes(1)))
+    @MainActor func notificationCenterPublisher() async {
+        var cancellables = Set<AnyCancellable>()
+        let center = NotificationCenter()
+        nonisolated(unsafe) var received = false
+        center.publisher(for: HitchhikersNotification.self)
+            .sink { hitchhikers in
+                #expect(hitchhikers.answer == 42)
+                received = true
+            }.store(in: &cancellables)
+        await Task.yield()
+
+        let hitchhikers = HitchhikersNotification(answer: 42)
+        center.post(.better(hitchhikers))
+        while !received { await Task.yield() }
+    }
+
+    @Test(.timeLimit(.minutes(1)))
+    @MainActor func notificationCenterPublisherIgnoresInvalidPayloads() async throws {
+        var cancellables = Set<AnyCancellable>()
+        let center = NotificationCenter()
+        nonisolated(unsafe) var received = false
+        center.publisher(for: HitchhikersNotification.self)
+            .sink { hitchhikers in
+                #expect(hitchhikers.answer == 42)
+                received = true
+            }.store(in: &cancellables)
+        await Task.yield()
+
+        // Post an invalid one that should be ignored.
+        let imposter = Notification(
+            name: HitchhikersNotification.notificationName,
+            object: nil,
+            userInfo: [HitchhikersNotification.userInfoKey: "imposter"]
+        )
+        center.post(imposter)
+
+        try await Task.sleep(for: .milliseconds(10))
+        #expect(!received)
+    }
 }

Tests/BetterNotificationTests/HitchhikersNotification.swift

@@ -0,0 +1,5 @@
+import BetterNotification
+
+struct HitchhikersNotification: BetterNotification, Equatable {
+    let answer: Int
+}