Wing Tips: Working with Tests and AI Agents in Wing Pro 12

Jul 10, 2026

This Wing Tip continues the series on AI agents in Wing Pro 12. Tests give the agent concrete feedback on whether a change is correct, and give you concrete evidence to review even before reading the diff.

Testing Regimen

Wing provides the agent with a variety of capabilities aimed at making its work more efficient and reducing token consumption. Part of this comes in the form of MCP (Model Context Protocol) servers that it uses to access Wing functionality in ways that make it more efficient.

Another part takes the form of development guides, which Wing writes into the .wing directory when you set up the agent. These describe the development methodology to follow, and nudge the agent towards using the MCP tools in a way that reduces wall time and token use.

Some of the larger gains seen in our benchmarks, which were run with Claude Code, were the result of providing the agent with a unit testing capability optimized for token use and guidance on how to do testing as it develops code.

You can control the details of this from the AI Agent tab in Project Properties. By default -- the Minimal regimen -- Wing asks the agent to write tests for new code and run those new tests before considering a task complete.

You can also request other unit testing modes, each of which varies guidance on when to write tests and when to run them.

Note that if you change the Testing Regimen or its individual parameters, that change will only apply to new agent sessions and not any sessions that are already running.

Running Tests via Wing's Testing Tool

The agent uses the same Testing tool you'd use yourself, configured through the Testing tab in Project Properties (see the Unit Testing Wing Tip). This means:

The agent picks up your project's test file configuration
Failures appear in the Testing tool with the same drill-down as manual runs.
Code coverage data is available to both you and the agent

Results update in the Testing tool as they come in, so you can watch a long suite progress without interrupting the agent.

You don't have to spell all of this out in a prompt every time. The Write Tests item in the Testing menu and editor context menu hands selected code to the agent to write tests for, and when a test fails the Testing tool offers a one-click FIX that sends the failure straight to the agent to diagnose and resolve.

Testing tool while the agent is running tests

Shown above: Watching the Testing tool update in real time while the agent runs the test suite as part of an in-progress task.

Code Coverage

When an agent uses Wing's unit testing MCP server, it always runs tests with code coverage enabled. This allows it to run just stale tests after making code changes, which can save a lot of time and token usage.

A few things to understand about code coverage:

Code coverage does not mean that code is correct; that depends on whether the unit tests are correct and passing.
Code coverage is not infallible, but it's a great heuristic for reducing development time and token use.

You should still run all your unit tests before releasing your code to production. There is no absolute guarantee that every necessary test run has taken place, if you are relying entirely on code coverage to decide which tests to run.

Tests matter even more when agents work autonomously with the Tasks Manager: without them, workers can't tell whether their code functions correctly, and the work stops often to ask you. See the Wing Tip on autonomous development.

Testing Regimen

Running Tests via Wing's Testing Tool

Code Coverage

Further Reading