# Verify an adapter

> Test a storage adapter before users trust it with their work. verifyStorageAdapter checks save conflict handling, revisions, overwrite and versions.

Source: https://fabricjs-document-engine.jscrate.dev/docs/storage/verify-adapter
Last updated: 2026-09-28

A storage adapter that gets one rule wrong can lose work quietly. The fastest way to test a storage adapter is `verifyStorageAdapter`. It runs the storage contract against your adapter and reports each check.

## Run the check

```ts
import { verifyStorageAdapter } from "fabricjs-document-engine/storage";

const report = await verifyStorageAdapter(restStorage);
if (!report.ok) console.table(report.checks);
```

`report` is `{ ok, checks }`. Each check is `{ name, passed, message }`.

## What it checks

| Check                                                        | Why it matters                                |
| ------------------------------------------------------------ | --------------------------------------------- |
| Saves a new document when `expectedRevision` is 0            | New documents can be stored                   |
| Loads the document it saved                                  | What you save is what you get back            |
| Refuses a save based on an old revision with `SAVE_CONFLICT` | Another tab cannot overwrite newer work       |
| Accepts a save based on the current revision                 | Normal saves still work                       |
| Overwrites when `expectedRevision` is `null`                 | "Keep my version" after a save conflict works |
| Rejects loading a document that does not exist               | Missing documents fail clearly                |
| Keeps, lists, loads and deletes versions                     | Only when the adapter has version methods     |

The check writes test documents with random ids. When your adapter has a `deleteDocument` method, it removes them afterwards.

## Where to run it

Run it once in development against a test database, or in your test suite:

```ts
import { expect, test } from "vitest";
import { verifyStorageAdapter } from "fabricjs-document-engine/storage";

test("the REST adapter follows the save rules", async () => {
  const report = await verifyStorageAdapter(restStorage);
  expect(report.checks.filter((check) => !check.passed)).toEqual([]);
});
```

Do not run it against production data. When you test a storage adapter this way on every change, a broken revision check fails the build instead of a user's save.