feat: update readme for schema testing

tests/schema/README.md

@@ -1 +1,88 @@
-Before running tests, start Drupal from `apps/cms` with `pnpm dev`
+# GraphQL Schema Testing with Vitest
+
+## Overview
+
+This guide provides instructions on how to write and run schema tests for
+GraphQL queries in a project that uses Gatsby and Drupal. The purpose of these
+tests is to ensure that the GraphQL schema remains consistent and to verify that
+the responses match expected formats.
+
+## Test Framework
+
+We use Vitest for testing:
+
+- Simple and popular, works in various environments including command line and
+  IDEs.
+- Supports inline snapshots, which are crucial for our schema testing strategy.
+
+## Writing Tests
+
+### General Strategy
+
+- **Coverage**: Aim to cover each GraphQL type and field.
+- **Modularity**: Write small, modular tests with one test per type or content
+  item to avoid large, complex snapshots.
+- **Snapshot Usage**: Inline snapshots make it easy to see right in the test
+  code what the output should be.
+- **Warning**: Be cautious with numeric IDs in snapshots as they can change
+  dynamically. Use path aliases when possible.
+
+### Steps to Create Tests
+
+1. **Prepare Your Environment**:
+
+   - Define your GraphQL schema and add resolvers.
+   - Create some default content that will be used in the tests.
+
+2. **Develop Test Cases**:
+
+   - In the `/tests/schema/specs` folder, create or modify a `.spec.ts` file for
+     your test.
+   - Use the `gql` tag from `noop-tag` for GraphQL queries to benefit from
+     autocomplete and autoformatting features.
+
+   **Example Test**:
+
+   ```typescript
+   import gql from 'noop-tag';
+   import { expect, test } from 'vitest';
+   import { fetch } from '../lib.js';
+
+   test('Baby', async () => {
+     const result = await fetch(gql`
+       {
+         _loadBaby(id: "uuid-of-node") {
+           name
+           path
+           picture {
+             __typename
+             uuid
+           }
+         }
+       }
+     `);
+     expect(result).toMatchInlineSnapshot();
+   });
+   ```
+
+   The test fetches data for a 'Baby' content type, checking if the name, path,
+   and picture data match what we expect.
+
+3. **Running Tests**:
+
+   - **Using PHPStorm**: In PHPStorm, you can run a specific test directly from
+     the IDE by clicking on the green arrow next to the test name.
+   - **Using the Command Line**:
+     - To run a specific test by name, use the `--match` option:
+       `vitest run --match "Test Name"`
+     - To run all tests within a file, run `vitest run your-test-file.spec.ts`
+     - Automatically run tests related to files as you make changes to them
+       using: `vitest run --watch`.
+   - The snapshot will appear inside `.toMatchInlineSnapshot()`, allowing you to
+     verify the returned data.
+
+### Additional Resources
+
+- [Vitest Documentation](https://vitest.dev/docs/): For more information on
+  testing and specific features of Vitest
+- [Noop-tag Readme](https://www.npmjs.com/package/noop-tag)