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Document Client usage with HTTPClientTransport (#77)
* Add test coverage for Client with HTTPClientTransport * Configure HTTP client transport to stream by default * Add example usage of streaming HTTP transport to README * Explicitly set streaming to false in test
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‎README.md

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Original file line numberDiff line numberDiff line change
@@ -39,6 +39,29 @@ try await client.connect(transport: transport)
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let result = try await client.initialize()
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```
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### Streaming HTTP Transport
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The HTTP transport supports streaming mode for real-time communication using Server-Sent Events (SSE):
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```swift
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import MCP
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// Create a streaming HTTP transport
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let transport = HTTPClientTransport(
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endpoint: URL(string: "http://localhost:8080")!,
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)
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// Initialize the client with streaming transport
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let client = Client(name: "MyApp", version: "1.0.0")
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try await client.connect(transport: transport)
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// Initialize the connection
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let result = try await client.initialize()
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// The transport will automatically handle SSE events
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// and deliver them through the client's notification handlers
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```
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### Basic Server Setup
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```swift

‎Sources/MCP/Base/Transports/HTTPClientTransport.swift

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Original file line numberDiff line numberDiff line change
@@ -21,7 +21,7 @@ public actor HTTPClientTransport: Actor, Transport {
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public init(
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endpoint: URL,
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configuration: URLSessionConfiguration = .default,
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streaming: Bool = false,
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streaming: Bool = true,
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logger: Logger? = nil
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) {
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self.init(
@@ -269,7 +269,7 @@ public actor HTTPClientTransport: Actor, Transport {
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if line.hasSuffix("\r") {
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line = line.dropLast()
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}
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// Lines starting with ":" are comments
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if line.hasPrefix(":") { continue }
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‎Tests/MCPTests/HTTPClientTransportTests.swift

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Original file line numberDiff line numberDiff line change
@@ -51,7 +51,11 @@ import Testing
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func executeHandler(for request: URLRequest) async throws -> (HTTPURLResponse, Data) {
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guard let handler = requestHandler else {
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throw MockURLProtocolError.noRequestHandler
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throw NSError(
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domain: "MockURLProtocolError", code: 0,
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userInfo: [
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NSLocalizedDescriptionKey: "No request handler set"
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])
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}
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return try await handler(request)
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}
@@ -123,11 +127,6 @@ import Testing
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override func stopLoading() {}
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}
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enum MockURLProtocolError: Swift.Error {
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case noRequestHandler
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case invalidURL
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}
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// MARK: -
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@Suite("HTTP Client Transport Tests", .serialized)
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configuration.protocolClasses = [MockURLProtocol.self]
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let transport = HTTPClientTransport(
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endpoint: testEndpoint, configuration: configuration, streaming: false, logger: nil)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: false,
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logger: nil
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)
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try await transport.connect()
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await transport.disconnect()
@@ -152,7 +155,11 @@ import Testing
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configuration.protocolClasses = [MockURLProtocol.self]
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let transport = HTTPClientTransport(
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endpoint: testEndpoint, configuration: configuration, streaming: false, logger: nil)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: false,
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logger: nil
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)
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try await transport.connect()
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let messageData = #"{"jsonrpc":"2.0","method":"initialize","id":1}"#.data(using: .utf8)!
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configuration.protocolClasses = [MockURLProtocol.self]
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let transport = HTTPClientTransport(
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endpoint: testEndpoint, configuration: configuration, streaming: false, logger: nil)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: false,
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logger: nil
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)
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try await transport.connect()
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let messageData = #"{"jsonrpc":"2.0","method":"initialize","id":1}"#.data(using: .utf8)!
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configuration.protocolClasses = [MockURLProtocol.self]
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let transport = HTTPClientTransport(
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endpoint: testEndpoint, configuration: configuration, streaming: false, logger: nil)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: false,
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logger: nil
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)
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try await transport.connect()
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let initialSessionID = "existing-session-abc"
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configuration.protocolClasses = [MockURLProtocol.self]
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let transport = HTTPClientTransport(
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endpoint: testEndpoint, configuration: configuration)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: false,
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logger: nil
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)
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try await transport.connect()
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let messageData = #"{"jsonrpc":"2.0","method":"test","id":3}"#.data(using: .utf8)!
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configuration.protocolClasses = [MockURLProtocol.self]
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let transport = HTTPClientTransport(
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endpoint: testEndpoint, configuration: configuration)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: false,
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logger: nil
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)
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try await transport.connect()
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let messageData = #"{"jsonrpc":"2.0","method":"test","id":4}"#.data(using: .utf8)!
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configuration.protocolClasses = [MockURLProtocol.self]
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let transport = HTTPClientTransport(
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endpoint: testEndpoint, configuration: configuration)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: false,
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logger: nil
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)
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try await transport.connect()
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let initialSessionID = "expired-session-xyz"
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385412
configuration.protocolClasses = [MockURLProtocol.self]
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let transport = HTTPClientTransport(
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endpoint: testEndpoint, configuration: configuration, streaming: true,
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logger: nil)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: true,
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logger: nil
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)
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391421
let eventString = "id: event1\ndata: {\"key\":\"value\"}\n\n"
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let sseEventData = eventString.data(using: .utf8)!
@@ -419,8 +449,11 @@ import Testing
419449
configuration.protocolClasses = [MockURLProtocol.self]
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421451
let transport = HTTPClientTransport(
422-
endpoint: testEndpoint, configuration: configuration, streaming: true,
423-
logger: nil)
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endpoint: testEndpoint,
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configuration: configuration,
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streaming: true,
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logger: nil
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)
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425458
let eventString = "id: event1\r\ndata: {\"key\":\"value\"}\r\n\n"
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let sseEventData = eventString.data(using: .utf8)!
@@ -448,6 +481,152 @@ import Testing
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#expect(receivedData == expectedData)
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}
450483
#endif // !canImport(FoundationNetworking)
451-
}
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@Test(
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"Client with HTTP Transport complete flow", .httpClientTransportSetup,
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.timeLimit(.minutes(1)))
488+
func testClientFlow() async throws {
489+
let configuration = URLSessionConfiguration.ephemeral
490+
configuration.protocolClasses = [MockURLProtocol.self]
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492+
let transport = HTTPClientTransport(
493+
endpoint: testEndpoint,
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configuration: configuration,
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streaming: false,
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logger: nil
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)
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499+
let client = Client(name: "TestClient", version: "1.0.0")
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// Use an actor to track request sequence
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actor RequestTracker {
503+
enum RequestType {
504+
case initialize
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case callTool
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}
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508+
private(set) var lastRequest: RequestType?
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510+
func setRequest(_ type: RequestType) {
511+
lastRequest = type
512+
}
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func getLastRequest() -> RequestType? {
515+
return lastRequest
516+
}
517+
}
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519+
let tracker = RequestTracker()
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// Setup mock responses
522+
await MockURLProtocol.requestHandlerStorage.setHandler {
523+
[testEndpoint, tracker] (request: URLRequest) in
524+
switch request.httpMethod {
525+
case "GET":
526+
#expect(
527+
request.allHTTPHeaderFields?["Accept"]?.contains("text/event-stream")
528+
== true)
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case "POST":
530+
#expect(
531+
request.allHTTPHeaderFields?["Accept"]?.contains("application/json") == true
532+
)
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default:
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Issue.record(
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"Unsupported HTTP method \(String(describing: request.httpMethod))")
536+
}
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538+
#expect(request.url == testEndpoint)
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let bodyData = request.readBody()
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guard let bodyData = bodyData,
543+
let json = try JSONSerialization.jsonObject(with: bodyData) as? [String: Any],
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let method = json["method"] as? String
545+
else {
546+
throw NSError(
547+
domain: "MockURLProtocolError", code: 0,
548+
userInfo: [
549+
NSLocalizedDescriptionKey: "Invalid JSON-RPC message \(#file):\(#line)"
550+
])
551+
}
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553+
if method == "initialize" {
554+
await tracker.setRequest(.initialize)
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556+
let requestID = json["id"] as! String
557+
let result = Initialize.Result(
558+
protocolVersion: Version.latest,
559+
capabilities: .init(tools: .init()),
560+
serverInfo: .init(name: "Mock Server", version: "0.0.1"),
561+
instructions: nil
562+
)
563+
let response = Initialize.response(id: .string(requestID), result: result)
564+
let responseData = try JSONEncoder().encode(response)
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566+
let httpResponse = HTTPURLResponse(
567+
url: testEndpoint, statusCode: 200, httpVersion: "HTTP/1.1",
568+
headerFields: ["Content-Type": "application/json"])!
569+
return (httpResponse, responseData)
570+
} else if method == "tools/call" {
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// Verify initialize was called first
572+
if let lastRequest = await tracker.getLastRequest(), lastRequest != .initialize
573+
{
574+
#expect(Bool(false), "Initialize should be called before callTool")
575+
}
576+
577+
await tracker.setRequest(.callTool)
578+
579+
let params = json["params"] as? [String: Any]
580+
let toolName = params?["name"] as? String
581+
#expect(toolName == "calculator")
582+
583+
let requestID = json["id"] as! String
584+
let result = CallTool.Result(content: [.text("42")])
585+
let response = CallTool.response(id: .string(requestID), result: result)
586+
let responseData = try JSONEncoder().encode(response)
587+
588+
let httpResponse = HTTPURLResponse(
589+
url: testEndpoint, statusCode: 200, httpVersion: "HTTP/1.1",
590+
headerFields: ["Content-Type": "application/json"])!
591+
return (httpResponse, responseData)
592+
} else if method == "notifications/initialized" {
593+
// Ignore initialized notifications
594+
let httpResponse = HTTPURLResponse(
595+
url: testEndpoint, statusCode: 200, httpVersion: "HTTP/1.1",
596+
headerFields: ["Content-Type": "application/json"])!
597+
return (httpResponse, Data())
598+
} else {
599+
throw NSError(
600+
domain: "MockURLProtocolError", code: 0,
601+
userInfo: [
602+
NSLocalizedDescriptionKey:
603+
"Unexpected request method: \(method) \(#file):\(#line)"
604+
])
605+
}
606+
}
607+
608+
// Execute the complete flow
609+
try await client.connect(transport: transport)
610+
611+
// Step 1: Initialize client
612+
let initResult = try await client.initialize()
613+
#expect(initResult.protocolVersion == Version.latest)
614+
#expect(initResult.capabilities.tools != nil)
615+
616+
// Step 2: Call a tool
617+
let toolResult = try await client.callTool(name: "calculator")
618+
#expect(toolResult.content.count == 1)
619+
if case let .text(text) = toolResult.content[0] {
620+
#expect(text == "42")
621+
} else {
622+
#expect(Bool(false), "Expected text content")
623+
}
624+
625+
// Step 3: Verify request sequence
626+
#expect(await tracker.getLastRequest() == .callTool)
627+
628+
// Step 4: Disconnect
629+
await client.disconnect()
630+
}
631+
}
453632
#endif // swift(>=6.1)

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