feat: add testing for the global configs

We want to make sure we aren't missing anything important.

test/vitest.d.ts

@@ -0,0 +1,19 @@
+/// <reference types="vitest" />
+
+import type { Assertion, AsymmetricMatchersContaining } from 'vitest';
+
+interface CustomMatchers<R = unknown> {
+  toContainRules(expected: Record<string, unknown>): R;
+}
+
+declare module 'vitest' {
+  interface Assertion<T = any> extends CustomMatchers<T> {}
+  interface AsymmetricMatchersContaining extends CustomMatchers {}
+}
+
+declare module 'vitest' {
+  // @ts-expect-error We need to extend the TestAPI interface
+  export interface TestAPI {
+    extend: <T>(matchers: Record<string, (this: T, ...args: any[]) => any>) => void;
+  }
+}