Add short document about JavaScriptEventLoopTestSupport

Author: kateinoigakukun

README.md

@@ -125,6 +125,23 @@ asyncButtonElement.onclick = .object(JSClosure { _ in
 _ = document.body.appendChild(asyncButtonElement)
 ```
 
+### `JavaScriptEventLoop` activation in XCTest suites
+
+If you need to execute Swift async functions that can be resumed by JS event loop in your XCTest suites, please add `JavaScriptEventLoopTestSupport` to your test target dependencies.
+
+```diff
+ .testTarget(
+   name: "MyAppTests",
+   dependencies: [
+     "MyApp",
++    "JavaScriptEventLoopTestSupport",
+   ]
+ )
+```
+
+Linking this module automatically activates JS event loop based global executor by calling `JavaScriptEventLoop.installGlobalExecutor()`
+
+
 ## Requirements 
 
 ### For developers

Sources/JavaScriptEventLoopTestSupport/JavaScriptEventLoopTestSupport.swift

@@ -1,8 +1,24 @@
-// This module just expose 'JavaScriptEventLoop.installGlobalExecutor' to C ABI
-// See _CJavaScriptEventLoopTestSupport.c for why this is needed
+/// If you need to execute Swift async functions that can be resumed by JS
+/// event loop in your XCTest suites, please add `JavaScriptEventLoopTestSupport`
+/// to your test target dependencies.
+///
+/// ```diff
+///  .testTarget(
+///    name: "MyAppTests",
+///    dependencies: [
+///      "MyApp",
+/// +    "JavaScriptEventLoopTestSupport",
+///    ]
+///  )
+/// ```
+///
+/// Linking this module automatically activates JS event loop based global
+/// executor by calling `JavaScriptEventLoop.installGlobalExecutor()`
 
 import JavaScriptEventLoop
 
+// This module just expose 'JavaScriptEventLoop.installGlobalExecutor' to C ABI
+// See _CJavaScriptEventLoopTestSupport.c for why this is needed
 @_cdecl("swift_javascriptkit_activate_js_executor_impl")
 func swift_javascriptkit_activate_js_executor_impl() {
     JavaScriptEventLoop.installGlobalExecutor()