Agent-Driven Development in Cursor: Testing, Benchmarking, and Optimizing Functions

Abstraction: Cursor agent writes tests, benchmarks, optimizes a function

Key points:

• Lesson demonstrates using Cursor IDE's Composer Agent to optimize a ~100-line calculateOrderPrices function without the human writing code — agent generates a 10-test unit suite, performance benchmarks, and 3 optimized variations.
• Workflow: @-mention the function, use agent mode, have it install deps and run tests, iterate on failures; then add a performance.test.ts with 5 scenarios and benchmark tracking in package.json.
• Practical friction points surfaced: agent kept using npm/yarn instead of pnpm (recommends adding to Cursor rules), left tests in watch mode, prematurely fixed linter errors, and repeatedly failed to export/define variations for tests.
• Outcome: variation C selected as winner, ~30% faster; whole run took ~45 minutes real-time (video heavily edited). Author speculates the Claude backend was underperforming that day.
• Takeaway: data-driven benchmarking validates optimizations with concrete metrics, but agent loops require patience, review, and repeated human intervention.

Connections: Cursor · Agentic Coding · Test Driven Development · Performance Benchmarking · AI Agents

Source: https://egghead.io/agent-driven-development-in-cursor-testing-benchmarking-and-optimizing-functions~7ousa