Testing and diagnostics

Use TypeScript and focused tests while editing, then widen the feedback loop as a change approaches release. Tavo.js diagnostics check the application shape and generated route contract without replacing tests for your product behavior.

bashnpx tsc --noEmit
npx tavo doctor
npx tavo check
npx tavo routes

createPagesTestHarness resolves an in-memory page map with the same route conventions used by the application. Use it for fast route, loader, middleware, and error-path tests; keep DOM interaction and hydration assertions in a real browser.

jsimport assert from "node:assert/strict";
import test from "node:test";
import { createPagesTestHarness } from "@tavojs/core/dev";

test("project route receives its loader data", async () => {
  const app = createPagesTestHarness({
    "/src/pages/projects/[id].tsx": {
      load: ({ params }) => ({ id: params.id, name: "Website" }),
      default: () => null,
    },
  });

  const result = await app.runtime.resolvePathAsync("/projects/42");
  assert.equal(result.status, 200);
  assert.equal(result.route?.path, "/projects/:id");
  assert.deepEqual(result.data, { id: "42", name: "Website" });
});

test("unknown URLs resolve to a 404", async () => {
  const app = createPagesTestHarness({
    "/src/pages/index.tsx": { default: () => null },
    "/src/pages/404.tsx": { default: () => null },
  });

  const result = await app.runtime.resolvePathAsync("/missing");
  assert.equal(result.status, 404);
});

Install and configure Playwright before using the browser-test command (npm install --save-dev @playwright/test, then npx playwright install). Add application tests and a configuration with the correct baseURL and server startup command. A production build discovers routes, compiles client and server output, prerenders static pages, and reports JavaScript cost. SSR preview exercises the generated server entry rather than the development transform pipeline.

• Exercise direct requests, client navigation, actions, 404 and error pages, and hydration in browser tests.

• Start npx tavo preview --ssr in a separate terminal for manual SSR checks, or configure it as Playwright's webServer.

• Inspect .tavo/generated/build-report.json when a route or shared first load grows unexpectedly.

• Add --max-first-load-js and --max-route-js limits when CI should enforce bundle budgets.

bashnpx tavo build --report-json
npx playwright test

Development diagnostics identify route, mount, patch, and hydration phases. Start with the first server-client divergence and its DOM path; suppressing the warning leaves the underlying ownership or rendering mismatch in place.

Production logs and instrumentation should record route patterns, phases, timing, and stable diagnostic codes. Exclude request bodies, cookies, tokens, and loader results unless the application has an explicit redaction policy.