What is livetest

Live Test Runner is a development tool you install as a devDependency. It watches your project, resolves which tests a change affects using the dependency graph, and runs only that subset, publishing the result on three channels at the same time: the terminal (for an AI agent), a structured log (for any tool), and a panel inside VSCode (for you).

$ livetest start

livetest batch-3 (idle) src/login.ts
  js -> 4 test file(s)
    src/footer.test.ts  ran because src/footer.ts imports src/login.ts (1 level)
    src/header.test.ts  ran because src/header.ts imports src/login.ts (1 level)
    src/layout.test.ts  ran because src/layout.ts imports src/login.ts via src/header.ts (2 levels)
    src/login.test.ts   ran because src/login.ts changed
  PASSED js  4 file(s)  5 passed  0 failed  0 skipped  1.5s
  batch-3 PASSED in 1.6s
LIVETEST batch=batch-3 status=passed files=4 tests=5 passed=5 failed=0 skipped=0 duration=1.6s

Why it exists#

Two recurring problems, both worse when the code is being written by an AI agent.

Late detection#

The real cycle is edit, edit, edit, and only then test. By the time the tests finally run, several changes have piled up, and isolating the one that broke something is expensive. An agent, meanwhile, has already taken half a dozen steps on top of a wrong assumption.

Underestimated scope#

Tools and agents tend to run only the tests of the file that changed, ignoring whatever depends on it. login.ts breaks, but the ones reporting it are the tests of header.ts and footer.ts, which nobody ran. The regression slips through.

The difference#

Live Test Runner is designed from the root for two simultaneous consumers: the agent, which needs to know immediately whether something broke, and the person, who wants to see it in the editor. On top of that it gives you configurable, per-file control of how deep the run propagates through the graph.

There is a fuller breakdown in Comparison.

What you get#

• A real dependency graph. JS/TS through the TypeScript compiler API, resolving paths, baseUrl, index.* and the ./x.js to ./x.ts mapping of ESM projects. Python through the native ast module, with relative and absolute imports.
• Every selection explained. No test runs without an import chain attached to justify it. livetest why src/login.ts prints the whole path before you change anything.
• Three output channels at once. A grepable summary line, an atomically written status.json snapshot, and an append-only NDJSON log with the full history.
• Safe degradation. Python missing, adapter broken, port unavailable: the daemon emits an error event saying what took over and keeps running.

Requirements#

Node.js 18.18 or newer. For Python projects, a 3.8+ interpreter on your PATH.