docs: fixes and improvements to testing docs (#11244)

* docs: fixes and improvements to testing docs

* generate files

www/apps/book/app/learn/debugging-and-testing/testing-tools/page.mdx

@@ -22,14 +22,6 @@ npm install --save-dev @medusajs/test-utils@latest
 
 Writing tests with `@medusajs/test-utils`'s tools requires installing and configuring Jest in your project.
 
-{/* TODO remove this note at some point in the future */}
-
-<Note>
-
-If your Medusa project was created after September 3rd, Jest is already installed and configured.
-
-</Note>
-
 Run the following command to install the required Jest dependencies:
 
 ```bash npm2yarn
@@ -56,6 +48,7 @@ module.exports = {
   testEnvironment: "node",
   moduleFileExtensions: ["js", "ts", "json"],
   modulePathIgnorePatterns: ["dist/"],
+  setupFiles: ["./integration-tests/setup.js"],
 }
 
 if (process.env.TEST_TYPE === "integration:http") {
@@ -67,6 +60,14 @@ if (process.env.TEST_TYPE === "integration:http") {
 }
 ```
 
+Next, create the `integration-tests/setup.js` file with the following content:
+
+```js title="integration-tests/setup.js"
+const { MetadataStorage } = require("@mikro-orm/core")
+
+MetadataStorage.clear()
+```
+
 ---
 
 ## Add Test Commands