Merge pull request #516 from testdouble/support-register

support Node v20.6.0 ability to auto-register loader

Author: giltayar

README.md

@@ -97,8 +97,7 @@ replaces all functions it encounters with fake test double functions which can,
 in turn, be configured by your test to either stub responses or assert
 invocations.
 
-Additionally, if you're using Node 13 or newer, you can specify testdouble as a
-module loader and replace native ES modules with `td.replaceEsm()`. More details
+Additionally, if you're using Node 16 or newer, you can replace native ES modules with `td.replaceEsm()`. More details
 [here](docs/7-replacing-dependencies.md#how-module-replacement-works-for-es-modules-using-import).
 
 #### Module replacement with Node.js

docs/7-replacing-dependencies.md

@@ -206,12 +206,15 @@ late to have their intended effect).
 
 ### How module replacement works for ES modules (using `import`)
 
-Under the hood, testdouble.js uses a loader (which you run using `node loader=testdouble`). A loader
+Under the hood, testdouble.js uses a loader. A loader
 is a module that can hook into the ES module loading mechanism in an official way. The testdouble
 loader ensures that if you call `td.replaceEsm` on an ES Module, the next time that module is loaded
 by Node.js, the source Node.js will get from the loader is not the regular source, but rather source
 code that contains some replacement code that can be used for the mock doubles.
 
+If you're using Node.js v20.6.0 or higher, the loader is registered automatically. But if you're using a lower
+version of Node.js, you must run Node with `--loader=testdouble`, or `td.replaceEsm` won't work.
+
 Also, every time you call `td.replaceEsm` on a module, you generate a new "generation" of that module, so
 that the next time Node.js loads that module, it loads the new generation of that replaced module.
 If you do `td.reset`, then the original module is loaded instead.