In the AI Era, Development Ability Is Determined by Verification Skills: Strategies for Rapid Validation and Local Environment Setup Learned While Developing the Flava API Gateway (opens in new tab)
AI coding agents iterate quickly, but their output can be inconsistent, make incorrect design decisions, or generate code that does not compile. Because CI runs, environment provisioning, and human review are slower, the article argues that reliable agent-assisted development requires three practices: spec-driven development, automated verification, and fast, self-contained local environments. ## Flava API Gateway and the Development Challenge - Flava API Gateway is part of LY Corporation’s private Flava cloud. - It provides a multi-tenant RESTful control-plane API for creating, deploying, and monitoring web APIs. - Kong serves as the data plane. - The team adopted agent-based coding while building the product and focused on preserving software reliability without sacrificing AI-driven speed. ## Spec-Driven Development The team found that agents became more unpredictable when implementation began before the design was settled. They use explicit specifications to reduce ambiguity and constrain implementation decisions. - OpenAPI is written before code to define the control-plane API. - Features are divided into smaller units and implemented with OpenSpec. - Specifications serve both as implementation guidance and as a standard for detecting deviations. ### Managing OpenAPI with Nickel - Raw OpenAPI YAML is repetitive and difficult to maintain manually. - Nickel is used to describe API resources declaratively and generate complete CRUD specifications. - A resource definition can specify: - Description and parent resource - Whether updates are allowed - Automatic timestamps - Property schemas - Required fields - Sorting and filtering behavior - The generator produces consistent endpoints such as `listPaths`, `createPath`, `getPath`, and `deletePath`. - Generated endpoints include pagination, sorting, filtering, ETags for optimistic locking, and standardized error responses. ### OpenSpec Workflow OpenSpec structures each change into four artifacts: - **Proposal:** Why the change is needed and what will change - **Design:** Technical decisions and trade-offs - **Delta specifications:** Behavioral requirements written as Given-When-Then scenarios - **Task list:** A step-by-step implementation checklist The developer and agent review the feature together, the agent creates these artifacts, and then implements the checklist incrementally. Once complete, the delta specification is archived into the main specification library, creating a versioned, evolving record of the system’s behavior. ## Automated Verification The team initially tried adding lists of pitfalls to prompts, but found this ineffective and potentially harmful. Instead, they made tests and tools reveal errors progressively so the agent could diagnose and correct them. - Automated tests, linters, and formatters provide precise feedback. - Failed tests identify what went wrong, allowing the agent to fix one issue before moving to the next. - Project-specific skills bundle these checks together. - `AGENTS.md` tells the agent when to load the relevant skills, avoiding unnecessary instructions on every turn. - Testing and linting are treated as essential infrastructure rather than optional activities, since agents frequently make errors during implementation. ## Fast, Independent Local Environments Relying on CI and shared test environments is too slow for agent-driven iteration. Long waits can disrupt the agent’s context and make repeated experimentation impractical. - A complete local environment provides immediate feedback. - Local dependencies make logs and state easier to inspect. - Developers avoid sending every failed attempt through a remote pipeline. - The local test suite contains 2,754 tests across three layers: - **Unit tests:** Isolated business logic - **Integration tests:** Real PostgreSQL, database constraints, triggers, soft-delete cascades, transactions, in-process HTTP, and OpenAPI compliance - **End-to-end tests:** Athenz authentication, Kong, API keys, and multi-tenant isolation - The full suite completes in roughly 15 seconds on a developer machine. - Parallel execution and strong test isolation are critical to achieving this speed. ## Practical Recommendation Agent-assisted development works best when agents are given clear behavioral contracts, immediate automated feedback, and a fast local loop. Teams should invest in specifications, comprehensive tests and linting, and realistic local dependencies so agents can correct mistakes continuously without waiting for CI.
