Add tests for a few race conditions

Package.swift

@@ -21,6 +21,7 @@ let package = Package(
             .product(name: "JWT", package: "jwt"),
         ]),
         .testTarget(name: "FCMTests", dependencies: [
+            .product(name: "VaporTesting", package: "vapor"),
             .target(name: "FCM"),
         ]),
     ]

Tests/FCMTests/FCMConcurrencyTests.swift

@@ -0,0 +1,95 @@
+import JWTKit
+import Testing
+import VaporTesting
+@testable import FCM
+
+@Suite("FCM Concurrency Tests")
+struct FCMConcurrencyTests {
+    @Test(
+        "Sending message right away should not crash",
+        .bug("https://github.com/MihaelIsaev/FCM/issues/57")
+    )
+    func sendMessageRightAwayAndDoNotCrash() async throws {
+        let message = FCMMessageDefault(token: "SOME_TOKEN", notification: nil)
+        try await withApp { app in
+            // Preload the request so we may use it right away
+            let request = request(on: app)
+            app.clients.use(.fcmTestResponder(.default))
+            app.fcm.configuration = .testing
+            _ = try await request.fcm.send(message)
+            try await waitForCacheWarmup()
+        }
+    }
+
+    @Test(
+        "Shutting the application down right away should not crash",
+        .bug("https://github.com/MihaelIsaev/FCM/issues/57")
+    )
+    func shutApplicationDownRightAwayAndDoNotCrash() async throws {
+        for _ in 0..<1000 {
+            try await withApp { app in
+                app.fcm.configuration = .testing
+            }
+        }
+        try await waitForCacheWarmup()
+    }
+
+    @Test(
+        "Resetting the configuration should not crash",
+        .bug("https://github.com/MihaelIsaev/FCM/issues/57")
+    )
+    func resetConfigurationAndDoNotCrash() async throws {
+        try await withApp { app in
+            for _ in 0..<1000 {
+                app.fcm.configuration = .testing
+                app.fcm.configuration = nil
+            }
+            try await waitForCacheWarmup()
+        }
+    }
+
+    @Test(
+        "Changing the configuration should invalidate credentials",
+        .bug("https://github.com/MihaelIsaev/FCM/issues/57")
+    )
+    func changeConfigurationAndInvalidateCredentials() async throws {
+        let newAccessToken = "NEW_ACCESS_TOKEN"
+        let newMessageName = "NEW_MESSAGE_NAME"
+        let newEmail = "new@test.aim.gserviceaccount.com"
+
+        var newResponder = FCMTestResponder.default
+        newResponder.accessToken { request in
+            let jwt = try #require(request.content.decode([String: String].self)["assertion"])
+            let payload = try await JWTKeyCollection().unverified(jwt, as: GAuthPayload.self)
+            #expect(payload.iss.value == newEmail)
+            return newAccessToken
+        }
+        newResponder.sendMessage { request in
+            #expect(request.headers.bearerAuthorization?.token == newAccessToken)
+            return newMessageName
+        }
+
+        let message = FCMMessageDefault(token: "SOME_TOKEN", notification: nil)
+        try await withApp { app in
+            app.clients.use(.fcmTestResponder(.default))
+            app.fcm.configuration = .testing
+            try await waitForCacheWarmup()
+            _ = try await request(on: app).fcm.send(message)
+
+            app.clients.use(.fcmTestResponder(newResponder))
+            app.fcm.configuration = .testing(email: newEmail)
+            try await waitForCacheWarmup()
+            _ = try await request(on: app).fcm.send(message)
+        }
+    }
+
+    func request(on app: Application) -> Request {
+        Request(application: app, on: app.eventLoopGroup.any())
+    }
+
+    func waitForCacheWarmup() async throws  {
+        // FCM perform a background task after changing the configuration.
+        // Not waiting for task to complete may cause race conditions.
+        try await Task.sleep(for: .milliseconds(100))
+    }
+}

Tests/FCMTests/FCMConfiguration+Testing.swift

@@ -0,0 +1,42 @@
+import FCM
+
+extension FCMConfiguration {
+    static let testing = FCMConfiguration.testing(email: "testing@test.aim.gserviceaccount.com")
+
+    static func testing(email: String) -> FCMConfiguration {
+        FCMConfiguration(
+            email: email,
+            projectId: "test",
+            key: """
+            -----BEGIN PRIVATE KEY-----
+            MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQCq2nhnp0uox5Yj
+            qEfv7BWYFD1VsyI+NksQSEp0lv2Jmq2DjtE3x7YklWCJimUXSpsRkuuTSfZigLvq
+            nWpC4v0YpYJcCwF2/MET2K9Qs0+qetETTb3JAuyPH7obC+gEtKQ5D5ZqSBHGy2xH
+            2kdCNIxH4fKqLcSR4IbzsXU10dARGyTugKpeVZ67FmcSxZtvEQIXwrCoKRVi8h78
+            aiaEGl6PWjPEp2tTo1iSHixfcEXAaqFtYjiZAcoYcVITR7dCmIj66Dxu2tHYWWgY
+            wMGL7d8VIADgtxJgt7lb1Bu6YuFxehM21N4jJFCSfJSwtzJXSAPCA/OH+VCCMirj
+            q760//u/AgMBAAECggEAAQeeECne9950FjTuchC/NJJyqDCTNULIgwmcgUVjs8+d
+            2hwjQK3QeDn6Qfn2kARgGOQEzXd1p7RU7Z4TROHvWpWsync6hAgT9dWpgNgD0+g3
+            mGEwkqSU3mv3iDAzLswT7VAdvPhAOy2AspIrOcftTIWdG894ztRGm/Nm3HMuSNwZ
+            e8PChu3fCa0CzQSmlHDBOjY0a+chl9T+3tBPaKjeTtgr2dhdSO45qlqaZFewWXJF
+            e6lgn49MpfsAQt22ohSurts40uOv+BDdX6eSEeN19PLgFbQ41adKfrpz2qBWAIga
+            tGYTwLuvcIXWnvaweI2G1vAkdUyVWl/xjNq+U64pSQKBgQDsDVWHiRHW2/UE/CL/
+            gTsEJvjZIFERYNrtwSNhYH+M+XVjrKWxo+6MLZ+A4O4MWfgz4x0wUFW+L7r2I7iF
+            KG/377OC6xWrhOL23oWdB+yWfr55eP6Y/HD15F+Z3dUR6H4i6kgdfykgyI6TepX3
+            phtdjznPWMbnXcaGDibEmd6xvQKBgQC5Sqa7/Ipx97oGr/FKNY7qhOxt0gRpyK0Y
+            ui/xOsG5yro8UOZruRjeKf3cyPzqPoKtGPE+HfKN/vma40MLWXfJukE+849y9j5r
+            tMIgVFmGii0C0SmK+Jw3dtdKEt8QblfQ3TfAw3RFCo9J7VdjXZIlkrhiw5XLrkYa
+            RXNcV7w1KwKBgH+Z+akppHYUMxA9yCF8V024T3735DrTs6UgaaLDClBHrXhzJKKx
+            bktigj2l2ajdnblWxTmPw7nqjVNvHdkFcfmCHvTfZbhxPkubIHkxhmgYHZkGmgJT
+            PDEAAdnoO7zRhBYVtWQUkEQDhmcctiLILTTXLrXyVJtPavief8B5ORO1AoGAUPQd
+            nro6XoqmGu/Z0ttNgobqqRx90x3bCpemBJXwN9Urwthxo5TuGXptMH4bidgfzbK9
+            C6+X3pQMx7ANBbNkE52tjexpuwd8xB/oRKm1p4NNIRLzPIVb8xuX+gP+szYSZe2Q
+            w0Zh0RxI+Dqa2I30IThWGMhs9N1CQY4gVbL7RpsCgYEAlUvnGI3YOMtb9COd5SrM
+            B/X+A9wifXF9+cTgngCdprJYv+VekWUSWa+jrMTbC2jURTtuOZzqgqNVdKNmfeUG
+            YntMAgkUKphW58LC5uU8VziNp686h40AQXQHAKXz984MWB1PpQgUria3ArYXlI0D
+            rG5mv3FiiqQSimO0AMir0JQ=
+            -----END PRIVATE KEY-----
+            """
+        )
+    }
+}

Tests/FCMTests/FCMTestResponder.swift

@@ -0,0 +1,78 @@
+import Vapor
+
+struct FCMTestResponder: Sendable {
+    mutating func respond(to url: URI, with response: ClientResponse) {
+        respond(to: url) { _ in response }
+    }
+
+    mutating func respond(to url: URI, with response: @Sendable @escaping (ClientRequest) async throws -> ClientResponse) {
+        responses[url] = response
+    }
+
+    mutating func accessToken(with perform: @Sendable @escaping (ClientRequest) async throws -> String) {
+        respond(to: "https://www.googleapis.com/oauth2/v4/token") { request in
+            let accessToken = try await perform(request)
+            var response = ClientResponse()
+            try response.content.encode(["access_token": accessToken])
+            return response
+        }
+    }
+
+    mutating func sendMessage(with perform: @Sendable @escaping (ClientRequest) async throws -> String) {
+        respond(to: "https://fcm.googleapis.com/v1/projects/test/messages:send") { request in
+            let name = try await perform(request)
+            var response = ClientResponse()
+            try response.content.encode(["name": name])
+            return response
+        }
+    }
+
+    func client(application: Application) -> Client {
+        Client(application: application, responder: self)
+    }
+
+    static let `default`: FCMTestResponder = {
+        var responder = FCMTestResponder()
+        responder.accessToken { _ in "DEFAULT_ACCESS_TOKEN" }
+        responder.sendMessage { _ in "DEFAULT_MESSAGE_NAME" }
+        return responder
+    }()
+
+    fileprivate var responses: [URI: @Sendable (ClientRequest) async throws -> ClientResponse] = [:]
+}
+
+extension FCMTestResponder {
+    struct Client: Vapor.Client {
+        let application: Application
+        let responder: FCMTestResponder
+
+        var eventLoop: EventLoop {
+            application.eventLoopGroup.any()
+        }
+
+        func delegating(to eventLoop: EventLoop) -> Vapor.Client {
+            self
+        }
+
+        func send(_ request: ClientRequest) -> EventLoopFuture<ClientResponse> {
+            let url = request.url
+            guard let response = responder.responses[url] else {
+                let error = Abort(.notImplemented, reason: "No registered response for url: '\(url)'.")
+                return eventLoop.future(error: error)
+            }
+            return eventLoop.makeFutureWithTask {
+                try await response(request)
+            }
+        }
+    }
+}
+
+extension Application.Clients.Provider {
+    static func fcmTestResponder(_ responder: FCMTestResponder) -> Application.Clients.Provider {
+        .init { application in
+            application.clients.use { application in
+                responder.client(application: application)
+            }
+        }
+    }
+}