Repository: nodejs/node
Pull request: doc: cover --experimental-test-module-mocks flag

As I discovered answering [this Stack Overflow question](https://stackoverflow.com/q/79004444/3001761), `node:test`'s [`mock.module`](https://nodejs.org/api/test.html#mockmodulespecifier-options) is currently hidden behind the `--experimental-test-module-mocks` flag. This was covered on the CLI page, but **not** the test runner page.

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Changed files:
filename: doc/api/test.md
patch: @@ -2112,8 +2112,10 @@ added: v22.3.0
 
 This function is used to mock the exports of ECMAScript modules, CommonJS
 modules, and Node.js builtin modules. Any references to the original module
-prior to mocking are not impacted. The following example demonstrates how a mock
-is created for a module.
+prior to mocking are not impacted. In order to enable module mocking, Node.js must
+be started with the [`--experimental-test-module-mocks`][] command-line flag.
+
+The following example demonstrates how a mock is created for a module.
 
 ```js
 test('mocks a builtin module in both module systems', async (t) => {
@@ -3561,6 +3563,7 @@ Can be used to abort test subtasks when the test has been aborted.
 
 [TAP]: https://testanything.org/
 [`--experimental-test-coverage`]: cli.md#--experimental-test-coverage
+[`--experimental-test-module-mocks`]: cli.md#--experimental-test-module-mocks
 [`--experimental-test-snapshots`]: cli.md#--experimental-test-snapshots
 [`--import`]: cli.md#--importmodule
 [`--test-concurrency`]: cli.md#--test-concurrency