Initial implementation

Tests/MCPTests/NotificationTests.swift

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+import Testing
+
+import class Foundation.JSONDecoder
+import class Foundation.JSONEncoder
+
+@testable import MCP
+
+@Suite("Notification Tests")
+struct NotificationTests {
+    struct TestNotification: Notification {
+        struct Parameters: Codable, Hashable, Sendable {
+            let event: String
+        }
+        static let name = "test.notification"
+    }
+
+    struct InitializedNotification: Notification {
+        static let name = "notifications/initialized"
+    }
+
+    @Test("Notification initialization with parameters")
+    func testNotificationWithParameters() throws {
+        let params = TestNotification.Parameters(event: "test-event")
+        let notification = TestNotification.message(params)
+
+        #expect(notification.method == TestNotification.name)
+        #expect(notification.params.event == "test-event")
+
+        let encoder = JSONEncoder()
+        let decoder = JSONDecoder()
+
+        let data = try encoder.encode(notification)
+        let decoded = try decoder.decode(Message<TestNotification>.self, from: data)
+
+        #expect(decoded.method == notification.method)
+        #expect(decoded.params.event == notification.params.event)
+    }
+
+    @Test("Empty parameters notification")
+    func testEmptyParametersNotification() throws {
+        struct EmptyNotification: Notification {
+            static let name = "empty.notification"
+        }
+
+        let notification = EmptyNotification.message()
+
+        let encoder = JSONEncoder()
+        let decoder = JSONDecoder()
+
+        let data = try encoder.encode(notification)
+        let decoded = try decoder.decode(Message<EmptyNotification>.self, from: data)
+
+        #expect(decoded.method == notification.method)
+    }
+
+    @Test("Initialized notification encoding")
+    func testInitializedNotificationEncoding() throws {
+        let notification = InitializedNotification.message()
+
+        let encoder = JSONEncoder()
+        let decoder = JSONDecoder()
+
+        let data = try encoder.encode(notification)
+
+        // Verify the exact JSON structure
+        let json = try JSONDecoder().decode([String: Value].self, from: data)
+        #expect(json["jsonrpc"] == "2.0")
+        #expect(json["method"] == "notifications/initialized")
+        #expect(json.count == 2, "Should only contain jsonrpc and method fields")
+
+        // Verify we can decode it back
+        let decoded = try decoder.decode(Message<InitializedNotification>.self, from: data)
+        #expect(decoded.method == InitializedNotification.name)
+    }
+
+    @Test("Initialized notification decoding")
+    func testInitializedNotificationDecoding() throws {
+        // Create a minimal JSON string
+        let jsonString = """
+            {"jsonrpc":"2.0","method":"notifications/initialized"}
+            """
+        let data = jsonString.data(using: .utf8)!
+
+        let decoder = JSONDecoder()
+        let decoded = try decoder.decode(Message<InitializedNotification>.self, from: data)
+
+        #expect(decoded.method == InitializedNotification.name)
+    }
+}