Struct TestClient 

pub struct TestClient { /* private fields */ }

Test client for in-process MCP testing.

Unlike the production Client, this works with MemoryTransport for fast, in-process testing without subprocess spawning.

Example

use fastmcp_rust::testing::prelude::*;

let (router, client_transport, server_transport) = TestServer::builder()
    .with_tool(my_tool)
    .build();
// Run server in a background thread (omitted here). Prefer using the
// higher-level E2E harness helpers in this crate which join threads on drop.

// Create test client
let mut client = TestClient::new(client_transport);
client.initialize().unwrap();

// Test operations
let tools = client.list_tools().unwrap();
assert!(!tools.is_empty());

Implementations

impl TestClient

pub fn new(transport: MemoryTransport) -> Self

Creates a new test client with the given transport.

Example

let (client_transport, server_transport) = create_memory_transport_pair();
let client = TestClient::new(client_transport);

pub fn with_cx(transport: MemoryTransport, cx: Cx) -> Self

Creates a new test client with custom Cx.

pub fn with_client_info( self, name: impl Into<String>, version: impl Into<String>, ) -> Self

Sets the client info for initialization.

pub fn with_capabilities(self, capabilities: ClientCapabilities) -> Self

Sets the client capabilities for initialization.

pub fn initialize(&mut self) -> McpResult<InitializeResult>

Performs the MCP initialization handshake.

Must be called before any other operations.

Errors

Returns an error if the initialization fails.

pub fn is_initialized(&self) -> bool

Returns whether the client has been initialized.

pub fn server_info(&self) -> Option<&ServerInfo>

Returns the server info after initialization.

pub fn server_capabilities(&self) -> Option<&ServerCapabilities>

Returns the server capabilities after initialization.

pub fn protocol_version(&self) -> Option<&str>

Returns the protocol version after initialization.

pub fn list_tools(&mut self) -> McpResult<Vec<Tool>>

Lists available tools.

Errors

Returns an error if the request fails.

pub fn call_tool( &mut self, name: &str, arguments: Value, ) -> McpResult<Vec<Content>>

Calls a tool with the given arguments.

Errors

Returns an error if the tool call fails.

pub fn list_resources(&mut self) -> McpResult<Vec<Resource>>

Lists available resources.

Errors

Returns an error if the request fails.

pub fn list_resource_templates(&mut self) -> McpResult<Vec<ResourceTemplate>>

Lists available resource templates.

Errors

Returns an error if the request fails.

pub fn read_resource(&mut self, uri: &str) -> McpResult<Vec<ResourceContent>>

Reads a resource by URI.

Errors

Returns an error if the resource cannot be read.

pub fn list_prompts(&mut self) -> McpResult<Vec<Prompt>>

Lists available prompts.

Errors

Returns an error if the request fails.

pub fn get_prompt( &mut self, name: &str, arguments: HashMap<String, String>, ) -> McpResult<Vec<PromptMessage>>

Gets a prompt with the given arguments.

Errors

Returns an error if the prompt cannot be retrieved.

pub fn send_raw_request( &mut self, method: &str, params: Value, ) -> McpResult<Value>

Sends a raw JSON-RPC request and returns the raw response.

Useful for testing custom or non-standard methods.

Errors

Returns an error if the request fails.

pub fn close(&mut self)

Closes the client connection.

pub fn transport(&self) -> &MemoryTransport

Returns a reference to the transport for advanced testing.

pub fn transport_mut(&mut self) -> &mut MemoryTransport

Returns a mutable reference to the transport for advanced testing.

pub fn send_request_json( &mut self, method: &str, params_value: Value, ) -> McpResult<Value>

Sends a raw JSON-RPC request with already-serialized params.

This is intended for advanced E2E tests that need to inject protocol fields not covered by the typed helper methods (for example, auth metadata).

Errors

Returns an error if the request fails or the response contains an error payload.

Trait Implementations

impl Debug for TestClient

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.