Testing

This section contains checking and testing strategies, processes, and test pages used by website tests and deployed live checks.

This section is under construction.

Test assertions

Goal

When a test fails, the output should make it obvious what was being checked and show a clear diff between actual and expected values, without long hand-written messages.

For example, avoid:

assert.ok(a === b, `expected ${a} to be ${b}`);

Instead favor:

assert.strictEqual(status, expectedStatus, 'HTTP status');

Guidance

The points below use Node’s built-in node:test runner and assert API because that is what several of our test suites use. The same ideas apply in other test frameworks: prefer assertions that produce tight diffs, keep failure context short and specific, and extract shared helpers when the same check repeats.

1. Prefer assert.strictEqual over assert.equal for primitive checks where strictness and diff quality matter.
2. Add a short third argument as context, for example HTTP status, Content-Type, Location, Request body.
3. Use assert.match when a regular expression can capture the intent more clearly than includes or chained ok logic.
4. Put shared assertion helpers in a module imported by the test suites that use them, colocated with those tests instead of copy-pasted across files. Other small, test-only utilities can live in the same module when it stays focused (for example assertVaryIncludesAccept in netlify/edge-functions/lib/test-helpers.ts).