test(harness): implement MCP JSON-RPC test harness

[anubhav756]

Overview

This PR introduces the native MCP test harness, enabling us to run integration tests using the JSON-RPC protocol over /mcp.

Changes

• Added tests/mcp_execute.go and tests/mcp_types.go as the core harness for invoking MCP tools and asserting responses.
• Updated tests/server.go to support dynamic flags like --enable-api.
• Added unit/integration tests in internal/server/server_test.go to verify the harness itself.

Checklist

• Ensure the tests and linter pass

[gemini-code-assist]

Summary of Changes

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This pull request introduces a dedicated test helper for the MCP JSON-RPC interface. The primary goal is to simplify the process of invoking and validating tool calls within the test suite, thereby improving testability and reducing boilerplate code for future MCP-related tests.

Highlights

• New MCP JSON-RPC Test Helper: A new Go function, ExecuteMCPToolCall, has been implemented to streamline the testing of MCP JSON-RPC tool calls. This helper abstracts away the complexities of request construction, HTTP communication, and response parsing, making it easier to write and maintain tests for MCP functionality.

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[gemini-code-assist]

Code Review

This pull request introduces a new test helper function, ExecuteMCPToolCall, in tests/mcp_execute.go. This function streamlines the process of making MCP tool calls within integration tests, handling request marshaling, HTTP communication, and response parsing. Feedback includes addressing the concatenation of multiple TextContent parts in the MCP response to ensure valid JSON output, and handling the error returned by json.Marshal during request body preparation.

[github-actions]

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