From ad85de426bcaf75dd2cd61f6750af8f65d2f2cd8 Mon Sep 17 00:00:00 2001
From: Peter Wagenet <peter.wagenet@gmail.com>
Date: Thu, 12 May 2022 12:23:28 -0700
Subject: [PATCH 1/2] Convert ember-testing to TS

---
 .../@ember/-internals/error-handling/index.ts |  4 +-
 .../@ember/application/lib/application.ts     | 12 +++-
 packages/@ember/application/lib/lazy_load.ts  |  2 +-
 packages/@ember/debug/index.ts                |  2 +-
 packages/@ember/engine/index.ts               |  3 +-
 packages/ember-testing/{index.js => index.ts} |  0
 .../lib/adapters/{adapter.js => adapter.ts}   | 11 +++-
 .../lib/adapters/{qunit.js => qunit.ts}       | 23 ++++++--
 .../ext/{application.js => application.ts}    | 49 +++++++++++-----
 packages/ember-testing/lib/ext/rsvp.js        | 19 -------
 packages/ember-testing/lib/ext/rsvp.ts        | 22 ++++++++
 .../lib/{helpers.js => helpers.ts}            |  0
 .../ember-testing/lib/helpers/and_then.js     |  3 -
 .../ember-testing/lib/helpers/and_then.ts     |  8 +++
 .../{current_path.js => current_path.ts}      | 12 +++-
 ...nt_route_name.js => current_route_name.ts} | 12 +++-
 .../ember-testing/lib/helpers/current_url.js  | 27 ---------
 .../ember-testing/lib/helpers/current_url.ts  | 37 ++++++++++++
 .../helpers/{pause_test.js => pause_test.ts}  |  2 +-
 packages/ember-testing/lib/helpers/visit.js   | 42 --------------
 packages/ember-testing/lib/helpers/visit.ts   | 56 +++++++++++++++++++
 .../lib/helpers/{wait.js => wait.ts}          | 10 +++-
 packages/ember-testing/lib/initializers.js    | 17 ------
 packages/ember-testing/lib/initializers.ts    | 19 +++++++
 ...up_for_testing.js => setup_for_testing.ts} |  6 +-
 .../ember-testing/lib/{test.js => test.ts}    |  0
 .../lib/test/{adapter.js => adapter.ts}       |  8 ++-
 .../lib/test/{helpers.js => helpers.ts}       | 19 +++++--
 ...inject_helpers.js => on_inject_helpers.ts} | 12 ++--
 ...ending_requests.js => pending_requests.ts} |  6 +-
 .../lib/test/{promise.js => promise.ts}       | 37 +++++++-----
 .../ember-testing/lib/test/{run.js => run.ts} |  2 +-
 .../lib/test/{waiters.js => waiters.ts}       | 36 ++++++++----
 33 files changed, 336 insertions(+), 182 deletions(-)
 rename packages/ember-testing/{index.js => index.ts} (100%)
 rename packages/ember-testing/lib/adapters/{adapter.js => adapter.ts} (83%)
 rename packages/ember-testing/lib/adapters/{qunit.js => qunit.ts} (70%)
 rename packages/ember-testing/lib/ext/{application.js => application.ts} (73%)
 delete mode 100644 packages/ember-testing/lib/ext/rsvp.js
 create mode 100644 packages/ember-testing/lib/ext/rsvp.ts
 rename packages/ember-testing/lib/{helpers.js => helpers.ts} (100%)
 delete mode 100644 packages/ember-testing/lib/helpers/and_then.js
 create mode 100644 packages/ember-testing/lib/helpers/and_then.ts
 rename packages/ember-testing/lib/helpers/{current_path.js => current_path.ts} (55%)
 rename packages/ember-testing/lib/helpers/{current_route_name.js => current_route_name.ts} (57%)
 delete mode 100644 packages/ember-testing/lib/helpers/current_url.js
 create mode 100644 packages/ember-testing/lib/helpers/current_url.ts
 rename packages/ember-testing/lib/helpers/{pause_test.js => pause_test.ts} (95%)
 delete mode 100644 packages/ember-testing/lib/helpers/visit.js
 create mode 100644 packages/ember-testing/lib/helpers/visit.ts
 rename packages/ember-testing/lib/helpers/{wait.js => wait.ts} (83%)
 delete mode 100644 packages/ember-testing/lib/initializers.js
 create mode 100644 packages/ember-testing/lib/initializers.ts
 rename packages/ember-testing/lib/{setup_for_testing.js => setup_for_testing.ts} (79%)
 rename packages/ember-testing/lib/{test.js => test.ts} (100%)
 rename packages/ember-testing/lib/test/{adapter.js => adapter.ts} (73%)
 rename packages/ember-testing/lib/test/{helpers.js => helpers.ts} (82%)
 rename packages/ember-testing/lib/test/{on_inject_helpers.js => on_inject_helpers.ts} (65%)
 rename packages/ember-testing/lib/test/{pending_requests.js => pending_requests.ts} (66%)
 rename packages/ember-testing/lib/test/{promise.js => promise.ts} (59%)
 rename packages/ember-testing/lib/test/{run.js => run.ts} (76%)
 rename packages/ember-testing/lib/test/{waiters.js => waiters.ts} (71%)

diff --git a/packages/@ember/-internals/error-handling/index.ts b/packages/@ember/-internals/error-handling/index.ts
index 6235842fcd0..405322b7b96 100644
--- a/packages/@ember/-internals/error-handling/index.ts
+++ b/packages/@ember/-internals/error-handling/index.ts
@@ -14,12 +14,12 @@ export function setOnerror(handler: Function) {
   onerror = handler;
 }
 
-let dispatchOverride: Function | undefined;
+let dispatchOverride: Function | null = null;
 
 // allows testing adapter to override dispatch
 export function getDispatchOverride() {
   return dispatchOverride;
 }
-export function setDispatchOverride(handler: Function) {
+export function setDispatchOverride(handler: Function | null) {
   dispatchOverride = handler;
 }
diff --git a/packages/@ember/application/lib/application.ts b/packages/@ember/application/lib/application.ts
index 87de87ba743..8a332f6ffa7 100644
--- a/packages/@ember/application/lib/application.ts
+++ b/packages/@ember/application/lib/application.ts
@@ -23,7 +23,7 @@ import {
 } from '@ember/-internals/routing';
 import type { BootOptions } from '../instance';
 import ApplicationInstance from '../instance';
-import Engine from '@ember/engine';
+import Engine, { buildInitializerMethod } from '@ember/engine';
 import type { Container, Registry } from '@ember/-internals/container';
 import { privatize as P } from '@ember/-internals/container';
 import { setupApplicationRegistry } from '@ember/-internals/glimmer';
@@ -220,6 +220,16 @@ class Application extends Engine {
     return registry;
   }
 
+  static initializer = buildInitializerMethod<'initializers', Application>(
+    'initializers',
+    'initializer'
+  );
+
+  static instanceInitializer = buildInitializerMethod<'instanceInitializers', ApplicationInstance>(
+    'instanceInitializers',
+    'instance initializer'
+  );
+
   /**
     The root DOM element of the Application. This can be specified as an
     element or a [selector string](https://developer.mozilla.org/en-US/docs/Learn/CSS/Building_blocks/Selectors#reference_table_of_selectors).
diff --git a/packages/@ember/application/lib/lazy_load.ts b/packages/@ember/application/lib/lazy_load.ts
index cf733e702a8..123e971ba2b 100644
--- a/packages/@ember/application/lib/lazy_load.ts
+++ b/packages/@ember/application/lib/lazy_load.ts
@@ -33,7 +33,7 @@ export let _loaded = loaded;
   @param callback {Function} callback to be called
   @private
 */
-export function onLoad(name: string, callback: (obj: unknown) => void) {
+export function onLoad(name: string, callback: (obj: any) => void) {
   let object = loaded[name];
 
   let hooks = (loadHooks[name] ??= []);
diff --git a/packages/@ember/debug/index.ts b/packages/@ember/debug/index.ts
index 168c0408d3a..c458b3e4be2 100644
--- a/packages/@ember/debug/index.ts
+++ b/packages/@ember/debug/index.ts
@@ -30,7 +30,7 @@ export type AssertFunc = (desc: string, condition?: unknown) => asserts conditio
 export type DebugFunc = (message: string) => void;
 export type DebugSealFunc = (obj: object) => void;
 export type DebugFreezeFunc = (obj: object) => void;
-export type InfoFunc = (message: string, options: object) => void;
+export type InfoFunc = (message: string, options?: object) => void;
 export type RunInDebugFunc = (func: () => void) => void;
 export type DeprecateFuncFunc = (
   message: string,
diff --git a/packages/@ember/engine/index.ts b/packages/@ember/engine/index.ts
index f27f649bf72..4c33154b453 100644
--- a/packages/@ember/engine/index.ts
+++ b/packages/@ember/engine/index.ts
@@ -467,7 +467,8 @@ function resolverFor(namespace: Engine) {
   return ResolverClass.create(props);
 }
 
-function buildInitializerMethod<
+/** @internal */
+export function buildInitializerMethod<
   B extends 'initializers' | 'instanceInitializers',
   T extends B extends 'initializers' ? Engine : EngineInstance
 >(bucketName: B, humanName: string) {
diff --git a/packages/ember-testing/index.js b/packages/ember-testing/index.ts
similarity index 100%
rename from packages/ember-testing/index.js
rename to packages/ember-testing/index.ts
diff --git a/packages/ember-testing/lib/adapters/adapter.js b/packages/ember-testing/lib/adapters/adapter.ts
similarity index 83%
rename from packages/ember-testing/lib/adapters/adapter.js
rename to packages/ember-testing/lib/adapters/adapter.ts
index 5fde61882b1..cba6d525a6e 100644
--- a/packages/ember-testing/lib/adapters/adapter.js
+++ b/packages/ember-testing/lib/adapters/adapter.ts
@@ -11,7 +11,12 @@ import { Object as EmberObject } from '@ember/-internals/runtime';
   @class TestAdapter
   @public
 */
-export default EmberObject.extend({
+interface Adapter extends EmberObject {
+  asyncStart(): void;
+  asyncEnd(): void;
+  exception(error: unknown): never;
+}
+const Adapter = EmberObject.extend({
   /**
     This callback will be called whenever an async operation is about to start.
 
@@ -48,7 +53,9 @@ export default EmberObject.extend({
     @method exception
     @param {String} error The exception to be raised.
   */
-  exception(error) {
+  exception(error: unknown) {
     throw error;
   },
 });
+
+export default Adapter;
diff --git a/packages/ember-testing/lib/adapters/qunit.js b/packages/ember-testing/lib/adapters/qunit.ts
similarity index 70%
rename from packages/ember-testing/lib/adapters/qunit.js
rename to packages/ember-testing/lib/adapters/qunit.ts
index eed764ceeb2..36b61f99da1 100644
--- a/packages/ember-testing/lib/adapters/qunit.js
+++ b/packages/ember-testing/lib/adapters/qunit.ts
@@ -2,6 +2,15 @@
 
 import { inspect } from '@ember/-internals/utils';
 import Adapter from './adapter';
+
+interface VeryOldQunit {
+  stop(): void;
+}
+
+function isVeryOldQunit(obj: unknown): obj is VeryOldQunit {
+  return obj != null && typeof (obj as VeryOldQunit).stop === 'function';
+}
+
 /**
    @module ember
 */
@@ -14,13 +23,15 @@ import Adapter from './adapter';
   @extends TestAdapter
   @public
 */
-export default Adapter.extend({
+// eslint-disable-next-line @typescript-eslint/no-empty-interface
+interface QUnitAdapter extends Adapter {}
+const QUnitAdapter = Adapter.extend({
   init() {
     this.doneCallbacks = [];
   },
 
   asyncStart() {
-    if (typeof QUnit.stop === 'function') {
+    if (isVeryOldQunit(QUnit)) {
       // very old QUnit version
       // eslint-disable-next-line qunit/no-qunit-stop
       QUnit.stop();
@@ -28,11 +39,12 @@ export default Adapter.extend({
       this.doneCallbacks.push(QUnit.config.current ? QUnit.config.current.assert.async() : null);
     }
   },
+
   asyncEnd() {
     // checking for QUnit.stop here (even though we _need_ QUnit.start) because
     // QUnit.start() still exists in QUnit 2.x (it just throws an error when calling
     // inside a test context)
-    if (typeof QUnit.stop === 'function') {
+    if (isVeryOldQunit(QUnit)) {
       QUnit.start();
     } else {
       let done = this.doneCallbacks.pop();
@@ -42,7 +54,10 @@ export default Adapter.extend({
       }
     }
   },
-  exception(error) {
+
+  exception(error: unknown) {
     QUnit.config.current.assert.ok(false, inspect(error));
   },
 });
+
+export default QUnitAdapter;
diff --git a/packages/ember-testing/lib/ext/application.js b/packages/ember-testing/lib/ext/application.ts
similarity index 73%
rename from packages/ember-testing/lib/ext/application.js
rename to packages/ember-testing/lib/ext/application.ts
index aaefc303179..11e497ea548 100644
--- a/packages/ember-testing/lib/ext/application.js
+++ b/packages/ember-testing/lib/ext/application.ts
@@ -5,6 +5,19 @@ import TestPromise, { resolve, getLastPromise } from '../test/promise';
 import run from '../test/run';
 import { invokeInjectHelpersCallbacks } from '../test/on_inject_helpers';
 import { asyncStart, asyncEnd } from '../test/adapter';
+import type Application from '@ember/application';
+import type { AnyFn } from '@ember/-internals/utils/types';
+import { assert } from '@ember/debug';
+
+export interface TestableApp extends Application {
+  testing?: boolean;
+  testHelpers: Record<string, (...args: unknown[]) => unknown>;
+  originalMethods: Record<string, (...args: unknown[]) => unknown>;
+  setupForTesting(): void;
+  helperContainer: object | null;
+  injectTestHelpers(helperContainer: unknown): void;
+  removeTestHelpers(): void;
+}
 
 EmberApplication.reopen({
   /**
@@ -105,7 +118,7 @@ EmberApplication.reopen({
     @method injectTestHelpers
     @public
   */
-  injectTestHelpers(helperContainer) {
+  injectTestHelpers(this: TestableApp, helperContainer: object) {
     if (helperContainer) {
       this.helperContainer = helperContainer;
     } else {
@@ -113,7 +126,7 @@ EmberApplication.reopen({
     }
 
     this.reopen({
-      willDestroy() {
+      willDestroy(this: TestableApp) {
         this._super(...arguments);
         this.removeTestHelpers();
       },
@@ -121,9 +134,12 @@ EmberApplication.reopen({
 
     this.testHelpers = {};
     for (let name in helpers) {
-      this.originalMethods[name] = this.helperContainer[name];
-      this.testHelpers[name] = this.helperContainer[name] = helper(this, name);
-      protoWrap(TestPromise.prototype, name, helper(this, name), helpers[name].meta.wait);
+      // SAFETY: It is safe to access a property on an object
+      this.originalMethods[name] = (this.helperContainer as any)[name];
+      // SAFETY: It is not quite as safe to do this, but it _seems_ to be ok.
+      this.testHelpers[name] = (this.helperContainer as any)[name] = helper(this, name);
+      // SAFETY: We checked that it exists
+      protoWrap(TestPromise.prototype, name, helper(this, name), helpers[name]!.meta.wait);
     }
 
     invokeInjectHelpersCallbacks(this);
@@ -149,7 +165,8 @@ EmberApplication.reopen({
 
     for (let name in helpers) {
       this.helperContainer[name] = this.originalMethods[name];
-      delete TestPromise.prototype[name];
+      // SAFETY: This is a weird thing, but it's not technically unsafe here.
+      delete (TestPromise.prototype as any)[name];
       delete this.testHelpers[name];
       delete this.originalMethods[name];
     }
@@ -159,26 +176,30 @@ EmberApplication.reopen({
 // This method is no longer needed
 // But still here for backwards compatibility
 // of helper chaining
-function protoWrap(proto, name, callback, isAsync) {
-  proto[name] = function (...args) {
+function protoWrap(proto: TestPromise<unknown>, name: string, callback: AnyFn, isAsync: boolean) {
+  // SAFETY: This isn't entirely safe, but it _seems_ to be ok.
+  (proto as any)[name] = function (...args: unknown[]) {
     if (isAsync) {
       return callback.apply(this, args);
     } else {
-      return this.then(function () {
+      // SAFETY: This is not actually safe.
+      return (this as any).then(function (this: any) {
         return callback.apply(this, args);
       });
     }
   };
 }
 
-function helper(app, name) {
-  let fn = helpers[name].method;
-  let meta = helpers[name].meta;
+function helper(app: TestableApp, name: string) {
+  let helper = helpers[name];
+  assert(`[BUG] Missing helper: ${name}`, helper);
+  let fn = helper.method;
+  let meta = helper.meta;
   if (!meta.wait) {
-    return (...args) => fn.apply(app, [app, ...args]);
+    return (...args: unknown[]) => fn.apply(app, [app, ...args]);
   }
 
-  return (...args) => {
+  return (...args: unknown[]) => {
     let lastPromise = run(() => resolve(getLastPromise()));
 
     // wait for last helper's promise to resolve and then
diff --git a/packages/ember-testing/lib/ext/rsvp.js b/packages/ember-testing/lib/ext/rsvp.js
deleted file mode 100644
index 814a40a5f0f..00000000000
--- a/packages/ember-testing/lib/ext/rsvp.js
+++ /dev/null
@@ -1,19 +0,0 @@
-import { RSVP } from '@ember/-internals/runtime';
-import { _backburner } from '@ember/runloop';
-import { isTesting } from '@ember/debug';
-import { asyncStart, asyncEnd } from '../test/adapter';
-
-RSVP.configure('async', function (callback, promise) {
-  // if schedule will cause autorun, we need to inform adapter
-  if (isTesting() && !_backburner.currentInstance) {
-    asyncStart();
-    _backburner.schedule('actions', () => {
-      asyncEnd();
-      callback(promise);
-    });
-  } else {
-    _backburner.schedule('actions', () => callback(promise));
-  }
-});
-
-export default RSVP;
diff --git a/packages/ember-testing/lib/ext/rsvp.ts b/packages/ember-testing/lib/ext/rsvp.ts
new file mode 100644
index 00000000000..51302fefeef
--- /dev/null
+++ b/packages/ember-testing/lib/ext/rsvp.ts
@@ -0,0 +1,22 @@
+import { RSVP } from '@ember/-internals/runtime';
+import { _backburner } from '@ember/runloop';
+import { isTesting } from '@ember/debug';
+import { asyncStart, asyncEnd } from '../test/adapter';
+
+RSVP.configure(
+  'async',
+  function (callback: (promise: Promise<unknown>) => void, promise: Promise<unknown>) {
+    // if schedule will cause autorun, we need to inform adapter
+    if (isTesting() && !_backburner.currentInstance) {
+      asyncStart();
+      _backburner.schedule('actions', () => {
+        asyncEnd();
+        callback(promise);
+      });
+    } else {
+      _backburner.schedule('actions', () => callback(promise));
+    }
+  }
+);
+
+export default RSVP;
diff --git a/packages/ember-testing/lib/helpers.js b/packages/ember-testing/lib/helpers.ts
similarity index 100%
rename from packages/ember-testing/lib/helpers.js
rename to packages/ember-testing/lib/helpers.ts
diff --git a/packages/ember-testing/lib/helpers/and_then.js b/packages/ember-testing/lib/helpers/and_then.js
deleted file mode 100644
index 5e451dccb95..00000000000
--- a/packages/ember-testing/lib/helpers/and_then.js
+++ /dev/null
@@ -1,3 +0,0 @@
-export default function andThen(app, callback) {
-  return app.testHelpers.wait(callback(app));
-}
diff --git a/packages/ember-testing/lib/helpers/and_then.ts b/packages/ember-testing/lib/helpers/and_then.ts
new file mode 100644
index 00000000000..ba38bca6520
--- /dev/null
+++ b/packages/ember-testing/lib/helpers/and_then.ts
@@ -0,0 +1,8 @@
+import { assert } from '@ember/debug';
+import type { TestableApp } from '../ext/application';
+
+export default function andThen(app: TestableApp, callback: (app: TestableApp) => unknown) {
+  let wait = app.testHelpers['wait'];
+  assert('[BUG] Missing wait helper', wait);
+  return wait(callback(app));
+}
diff --git a/packages/ember-testing/lib/helpers/current_path.js b/packages/ember-testing/lib/helpers/current_path.ts
similarity index 55%
rename from packages/ember-testing/lib/helpers/current_path.js
rename to packages/ember-testing/lib/helpers/current_path.ts
index a709da7639e..eb1523ab6ee 100644
--- a/packages/ember-testing/lib/helpers/current_path.js
+++ b/packages/ember-testing/lib/helpers/current_path.ts
@@ -2,6 +2,9 @@
 @module ember
 */
 import { get } from '@ember/-internals/metal';
+import { RoutingService } from '@ember/-internals/routing';
+import type Application from '@ember/application';
+import { assert } from '@ember/debug';
 
 /**
   Returns the current path.
@@ -21,7 +24,14 @@ click('#some-link-id').then(validateURL);
 @since 1.5.0
 @public
 */
-export default function currentPath(app) {
+export default function currentPath(app: Application) {
+  assert('[BUG] app.__container__ is not set', app.__container__);
+
   let routingService = app.__container__.lookup('service:-routing');
+  assert(
+    '[BUG] service:-routing is not a RoutingService',
+    routingService instanceof RoutingService
+  );
+
   return get(routingService, 'currentPath');
 }
diff --git a/packages/ember-testing/lib/helpers/current_route_name.js b/packages/ember-testing/lib/helpers/current_route_name.ts
similarity index 57%
rename from packages/ember-testing/lib/helpers/current_route_name.js
rename to packages/ember-testing/lib/helpers/current_route_name.ts
index 175c432d054..2e0ad85d0cb 100644
--- a/packages/ember-testing/lib/helpers/current_route_name.js
+++ b/packages/ember-testing/lib/helpers/current_route_name.ts
@@ -2,6 +2,9 @@
 @module ember
 */
 import { get } from '@ember/-internals/metal';
+import { RoutingService } from '@ember/-internals/routing';
+import type Application from '@ember/application';
+import { assert } from '@ember/debug';
 /**
   Returns the currently active route name.
 
@@ -19,7 +22,14 @@ visit('/some/path').then(validateRouteName)
 @since 1.5.0
 @public
 */
-export default function currentRouteName(app) {
+export default function currentRouteName(app: Application) {
+  assert('[BUG] app.__container__ is not set', app.__container__);
+
   let routingService = app.__container__.lookup('service:-routing');
+  assert(
+    '[BUG] service:-routing is not a RoutingService',
+    routingService instanceof RoutingService
+  );
+
   return get(routingService, 'currentRouteName');
 }
diff --git a/packages/ember-testing/lib/helpers/current_url.js b/packages/ember-testing/lib/helpers/current_url.js
deleted file mode 100644
index d5dd1ff5ed4..00000000000
--- a/packages/ember-testing/lib/helpers/current_url.js
+++ /dev/null
@@ -1,27 +0,0 @@
-/**
-@module ember
-*/
-import { get } from '@ember/-internals/metal';
-
-/**
-  Returns the current URL.
-
-Example:
-
-```javascript
-function validateURL() {
-  equal(currentURL(), '/some/path', "correct URL was transitioned into.");
-}
-
-click('#some-link-id').then(validateURL);
-```
-
-@method currentURL
-@return {Object} The currently active URL.
-@since 1.5.0
-@public
-*/
-export default function currentURL(app) {
-  let router = app.__container__.lookup('router:main');
-  return get(router, 'location').getURL();
-}
diff --git a/packages/ember-testing/lib/helpers/current_url.ts b/packages/ember-testing/lib/helpers/current_url.ts
new file mode 100644
index 00000000000..69148442667
--- /dev/null
+++ b/packages/ember-testing/lib/helpers/current_url.ts
@@ -0,0 +1,37 @@
+/**
+@module ember
+*/
+import { get } from '@ember/-internals/metal';
+import type Application from '@ember/application';
+import { assert } from '@ember/debug';
+import Router from '@ember/routing/router';
+
+/**
+  Returns the current URL.
+
+Example:
+
+```javascript
+function validateURL() {
+  equal(currentURL(), '/some/path', "correct URL was transitioned into.");
+}
+
+click('#some-link-id').then(validateURL);
+```
+
+@method currentURL
+@return {Object} The currently active URL.
+@since 1.5.0
+@public
+*/
+export default function currentURL(app: Application) {
+  assert('[BUG] app.__container__ is not set', app.__container__);
+
+  let router = app.__container__.lookup('router:main');
+  assert('[BUG] router:main is not a Router', router instanceof Router);
+
+  let location = get(router, 'location');
+  assert('[BUG] location is still a string', typeof location !== 'string');
+
+  return location.getURL();
+}
diff --git a/packages/ember-testing/lib/helpers/pause_test.js b/packages/ember-testing/lib/helpers/pause_test.ts
similarity index 95%
rename from packages/ember-testing/lib/helpers/pause_test.js
rename to packages/ember-testing/lib/helpers/pause_test.ts
index c4dd718035d..b0b2321fc35 100644
--- a/packages/ember-testing/lib/helpers/pause_test.js
+++ b/packages/ember-testing/lib/helpers/pause_test.ts
@@ -4,7 +4,7 @@
 import { RSVP } from '@ember/-internals/runtime';
 import { assert, info } from '@ember/debug';
 
-let resume;
+let resume: undefined | ((value?: unknown) => void);
 
 /**
  Resumes a test paused by `pauseTest`.
diff --git a/packages/ember-testing/lib/helpers/visit.js b/packages/ember-testing/lib/helpers/visit.js
deleted file mode 100644
index 326e61a713b..00000000000
--- a/packages/ember-testing/lib/helpers/visit.js
+++ /dev/null
@@ -1,42 +0,0 @@
-import { run } from '@ember/runloop';
-
-/**
-  Loads a route, sets up any controllers, and renders any templates associated
-  with the route as though a real user had triggered the route change while
-  using your app.
-
-  Example:
-
-  ```javascript
-  visit('posts/index').then(function() {
-    // assert something
-  });
-  ```
-
-  @method visit
-  @param {String} url the name of the route
-  @return {RSVP.Promise<undefined>}
-  @public
-*/
-export default function visit(app, url) {
-  let router = app.__container__.lookup('router:main');
-  let shouldHandleURL = false;
-
-  app.boot().then(() => {
-    router.location.setURL(url);
-
-    if (shouldHandleURL) {
-      run(app.__deprecatedInstance__, 'handleURL', url);
-    }
-  });
-
-  if (app._readinessDeferrals > 0) {
-    router.initialURL = url;
-    run(app, 'advanceReadiness');
-    delete router.initialURL;
-  } else {
-    shouldHandleURL = true;
-  }
-
-  return app.testHelpers.wait();
-}
diff --git a/packages/ember-testing/lib/helpers/visit.ts b/packages/ember-testing/lib/helpers/visit.ts
new file mode 100644
index 00000000000..e882ab7d58b
--- /dev/null
+++ b/packages/ember-testing/lib/helpers/visit.ts
@@ -0,0 +1,56 @@
+import { assert } from '@ember/debug';
+import Router from '@ember/routing/router';
+import { run } from '@ember/runloop';
+import type { TestableApp } from '../ext/application';
+
+/**
+  Loads a route, sets up any controllers, and renders any templates associated
+  with the route as though a real user had triggered the route change while
+  using your app.
+
+  Example:
+
+  ```javascript
+  visit('posts/index').then(function() {
+    // assert something
+  });
+  ```
+
+  @method visit
+  @param {String} url the name of the route
+  @return {RSVP.Promise<undefined>}
+  @public
+*/
+export default function visit(app: TestableApp, url: string) {
+  assert('[BUG] Missing container', app.__container__);
+
+  const router = app.__container__.lookup('router:main');
+  assert('[BUG] router:main is not a Router', router instanceof Router);
+
+  let shouldHandleURL = false;
+
+  app.boot().then(() => {
+    assert('[BUG] router.location is still a string', typeof router.location !== 'string');
+    router.location.setURL(url);
+
+    if (shouldHandleURL) {
+      assert("[BUG] __deprecatedInstance__ isn't set", app.__deprecatedInstance__);
+      run(app.__deprecatedInstance__, 'handleURL', url);
+    }
+  });
+
+  if (app._readinessDeferrals > 0) {
+    // SAFETY: This should be safe, though it is odd.
+    (router as any).initialURL = url;
+    run(app, 'advanceReadiness');
+    delete (router as any).initialURL;
+  } else {
+    shouldHandleURL = true;
+  }
+
+  let wait = app.testHelpers['wait'];
+
+  assert('[BUG] missing wait helper', wait);
+
+  return wait();
+}
diff --git a/packages/ember-testing/lib/helpers/wait.js b/packages/ember-testing/lib/helpers/wait.ts
similarity index 83%
rename from packages/ember-testing/lib/helpers/wait.js
rename to packages/ember-testing/lib/helpers/wait.ts
index 232a76ab9ce..631a76bfc5f 100644
--- a/packages/ember-testing/lib/helpers/wait.js
+++ b/packages/ember-testing/lib/helpers/wait.ts
@@ -5,6 +5,9 @@ import { checkWaiters } from '../test/waiters';
 import { RSVP } from '@ember/-internals/runtime';
 import { _getCurrentRunLoop, _hasScheduledTimers, run } from '@ember/runloop';
 import { pendingRequests } from '../test/pending_requests';
+import type Application from '@ember/application';
+import { assert } from '@ember/debug';
+import Router from '@ember/routing/router';
 
 /**
   Causes the run loop to process any pending events. This is used to ensure that
@@ -36,9 +39,12 @@ import { pendingRequests } from '../test/pending_requests';
   @public
   @since 1.0.0
 */
-export default function wait(app, value) {
+export default function wait<T>(app: Application, value: T): Promise<T> {
   return new RSVP.Promise(function (resolve) {
-    let router = app.__container__.lookup('router:main');
+    assert('[BUG] Missing container', app.__container__);
+
+    const router = app.__container__.lookup('router:main');
+    assert('[BUG] Expected router:main to be a subclass of Ember Router', router instanceof Router);
 
     // Every 10ms, poll for the async thing to have finished
     let watcher = setInterval(() => {
diff --git a/packages/ember-testing/lib/initializers.js b/packages/ember-testing/lib/initializers.js
deleted file mode 100644
index 0ff1d963fb6..00000000000
--- a/packages/ember-testing/lib/initializers.js
+++ /dev/null
@@ -1,17 +0,0 @@
-import { onLoad } from '@ember/application';
-
-let name = 'deferReadiness in `testing` mode';
-
-onLoad('Ember.Application', function (Application) {
-  if (!Application.initializers[name]) {
-    Application.initializer({
-      name: name,
-
-      initialize(application) {
-        if (application.testing) {
-          application.deferReadiness();
-        }
-      },
-    });
-  }
-});
diff --git a/packages/ember-testing/lib/initializers.ts b/packages/ember-testing/lib/initializers.ts
new file mode 100644
index 00000000000..debe4fdd517
--- /dev/null
+++ b/packages/ember-testing/lib/initializers.ts
@@ -0,0 +1,19 @@
+import { onLoad } from '@ember/application';
+import type Application from '@ember/application';
+import type { TestableApp } from './ext/application';
+
+let name = 'deferReadiness in `testing` mode';
+
+onLoad('Ember.Application', function (ApplicationClass: typeof Application) {
+  if (!ApplicationClass.initializers[name]) {
+    ApplicationClass.initializer({
+      name: name,
+
+      initialize(application) {
+        if ((application as TestableApp).testing) {
+          application.deferReadiness();
+        }
+      },
+    });
+  }
+});
diff --git a/packages/ember-testing/lib/setup_for_testing.js b/packages/ember-testing/lib/setup_for_testing.ts
similarity index 79%
rename from packages/ember-testing/lib/setup_for_testing.js
rename to packages/ember-testing/lib/setup_for_testing.ts
index 91c615d5fdb..7444158c262 100644
--- a/packages/ember-testing/lib/setup_for_testing.js
+++ b/packages/ember-testing/lib/setup_for_testing.ts
@@ -23,6 +23,10 @@ export default function setupForTesting() {
   let adapter = getAdapter();
   // if adapter is not manually set default to QUnit
   if (!adapter) {
-    setAdapter(typeof self.QUnit === 'undefined' ? Adapter.create() : QUnitAdapter.create());
+    setAdapter(
+      typeof (self as any).QUnit === 'undefined'
+        ? (Adapter.create() as Adapter)
+        : (QUnitAdapter.create() as QUnitAdapter)
+    );
   }
 }
diff --git a/packages/ember-testing/lib/test.js b/packages/ember-testing/lib/test.ts
similarity index 100%
rename from packages/ember-testing/lib/test.js
rename to packages/ember-testing/lib/test.ts
diff --git a/packages/ember-testing/lib/test/adapter.js b/packages/ember-testing/lib/test/adapter.ts
similarity index 73%
rename from packages/ember-testing/lib/test/adapter.js
rename to packages/ember-testing/lib/test/adapter.ts
index bfecab54869..610d7e60cab 100644
--- a/packages/ember-testing/lib/test/adapter.js
+++ b/packages/ember-testing/lib/test/adapter.ts
@@ -1,11 +1,12 @@
 import { setDispatchOverride } from '@ember/-internals/error-handling';
+import type Adapter from '../adapters/adapter';
 
-let adapter;
+let adapter: Adapter;
 export function getAdapter() {
   return adapter;
 }
 
-export function setAdapter(value) {
+export function setAdapter(value: Adapter) {
   adapter = value;
   if (value && typeof value.exception === 'function') {
     setDispatchOverride(adapterDispatch);
@@ -26,8 +27,9 @@ export function asyncEnd() {
   }
 }
 
-function adapterDispatch(error) {
+function adapterDispatch(error: unknown) {
   adapter.exception(error);
 
+  // @ts-expect-error Normally unreachable
   console.error(error.stack); // eslint-disable-line no-console
 }
diff --git a/packages/ember-testing/lib/test/helpers.js b/packages/ember-testing/lib/test/helpers.ts
similarity index 82%
rename from packages/ember-testing/lib/test/helpers.js
rename to packages/ember-testing/lib/test/helpers.ts
index 63a3774a8c9..4d278fd0a0e 100644
--- a/packages/ember-testing/lib/test/helpers.js
+++ b/packages/ember-testing/lib/test/helpers.ts
@@ -1,6 +1,13 @@
+import type { AnyFn } from '@ember/-internals/utils/types';
 import TestPromise from './promise';
 
-export const helpers = {};
+export const helpers: Record<
+  string,
+  {
+    method: AnyFn;
+    meta: { wait: boolean };
+  }
+> = {};
 /**
  @module @ember/test
 */
@@ -42,7 +49,7 @@ export const helpers = {};
   @param {Function} helperMethod
   @param options {Object}
 */
-export function registerHelper(name, helperMethod) {
+export function registerHelper(name: string, helperMethod: AnyFn) {
   helpers[name] = {
     method: helperMethod,
     meta: { wait: false },
@@ -95,7 +102,7 @@ export function registerHelper(name, helperMethod) {
   @param {Function} helperMethod
   @since 1.2.0
 */
-export function registerAsyncHelper(name, helperMethod) {
+export function registerAsyncHelper(name: string, helperMethod: AnyFn) {
   helpers[name] = {
     method: helperMethod,
     meta: { wait: true },
@@ -119,7 +126,9 @@ export function registerAsyncHelper(name, helperMethod) {
   @for @ember/test
   @param {String} name The helper to remove.
 */
-export function unregisterHelper(name) {
+export function unregisterHelper(name: string) {
   delete helpers[name];
-  delete TestPromise.prototype[name];
+  // SAFETY: This isn't necessarily a safe thing to do, but in terms of the immediate types here
+  // it won't error.
+  delete (TestPromise.prototype as any)[name];
 }
diff --git a/packages/ember-testing/lib/test/on_inject_helpers.js b/packages/ember-testing/lib/test/on_inject_helpers.ts
similarity index 65%
rename from packages/ember-testing/lib/test/on_inject_helpers.js
rename to packages/ember-testing/lib/test/on_inject_helpers.ts
index d4679f13855..b6f1c54122e 100644
--- a/packages/ember-testing/lib/test/on_inject_helpers.js
+++ b/packages/ember-testing/lib/test/on_inject_helpers.ts
@@ -1,4 +1,6 @@
-export const callbacks = [];
+import type Application from '@ember/application';
+
+export const callbacks: Array<(app: Application) => void> = [];
 
 /**
   Used to register callbacks to be fired whenever `App.injectTestHelpers`
@@ -27,12 +29,12 @@ export const callbacks = [];
   @method onInjectHelpers
   @param {Function} callback The function to be called.
 */
-export function onInjectHelpers(callback) {
+export function onInjectHelpers(callback: (app: Application) => void) {
   callbacks.push(callback);
 }
 
-export function invokeInjectHelpersCallbacks(app) {
-  for (let i = 0; i < callbacks.length; i++) {
-    callbacks[i](app);
+export function invokeInjectHelpersCallbacks(app: Application) {
+  for (let callback of callbacks) {
+    callback(app);
   }
 }
diff --git a/packages/ember-testing/lib/test/pending_requests.js b/packages/ember-testing/lib/test/pending_requests.ts
similarity index 66%
rename from packages/ember-testing/lib/test/pending_requests.js
rename to packages/ember-testing/lib/test/pending_requests.ts
index 7ebb01b7894..bd8bfbc0b31 100644
--- a/packages/ember-testing/lib/test/pending_requests.js
+++ b/packages/ember-testing/lib/test/pending_requests.ts
@@ -1,4 +1,4 @@
-let requests = [];
+let requests: unknown[] = [];
 
 export function pendingRequests() {
   return requests.length;
@@ -8,11 +8,11 @@ export function clearPendingRequests() {
   requests.length = 0;
 }
 
-export function incrementPendingRequests(_, xhr) {
+export function incrementPendingRequests(_: unknown, xhr: unknown) {
   requests.push(xhr);
 }
 
-export function decrementPendingRequests(_, xhr) {
+export function decrementPendingRequests(_: unknown, xhr: unknown) {
   setTimeout(function () {
     for (let i = 0; i < requests.length; i++) {
       if (xhr === requests[i]) {
diff --git a/packages/ember-testing/lib/test/promise.js b/packages/ember-testing/lib/test/promise.ts
similarity index 59%
rename from packages/ember-testing/lib/test/promise.js
rename to packages/ember-testing/lib/test/promise.ts
index 5ab18027d65..ccd095e98b7 100644
--- a/packages/ember-testing/lib/test/promise.js
+++ b/packages/ember-testing/lib/test/promise.ts
@@ -1,20 +1,31 @@
 import { RSVP } from '@ember/-internals/runtime';
 import run from './run';
 
-let lastPromise;
+let lastPromise: TestPromise<unknown> | null = null;
 
-export default class TestPromise extends RSVP.Promise {
-  constructor() {
-    super(...arguments);
+type Executor<T> = (
+  resolve: (value?: T | PromiseLike<T>) => void,
+  reject: (reason?: any) => void
+) => void;
+
+type OnFulfilled<T, TResult = T> = (value: T) => TResult | PromiseLike<TResult>;
+
+export default class TestPromise<T> extends RSVP.Promise<T> {
+  constructor(executor: Executor<T>, label?: string) {
+    super(executor, label);
     lastPromise = this;
   }
 
-  then(_onFulfillment, ...args) {
-    let onFulfillment =
-      typeof _onFulfillment === 'function'
-        ? (result) => isolate(_onFulfillment, result)
+  then<TResult1 = T, TResult2 = never>(
+    onFulfilled?: OnFulfilled<T, TResult1> | null,
+    onRejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null,
+    label?: string
+  ): RSVP.Promise<TResult1 | TResult2> {
+    let normalizedOnFulfilled =
+      typeof onFulfilled === 'function'
+        ? (result: T) => isolate<T, TResult1>(onFulfilled, result)
         : undefined;
-    return super.then(onFulfillment, ...args);
+    return super.then<TResult1, TResult2>(normalizedOnFulfilled, onRejected, label);
   }
 }
 
@@ -31,7 +42,7 @@ export default class TestPromise extends RSVP.Promise {
   @param {Function} resolver The function used to resolve the promise.
   @param {String} label An optional string for identifying the promise.
 */
-export function promise(resolver, label) {
+export function promise<T>(resolver: Executor<T>, label: string) {
   let fullLabel = `Ember.Test.promise: ${label || '<Unknown Promise>'}`;
   return new TestPromise(resolver, fullLabel);
 }
@@ -47,7 +58,7 @@ export function promise(resolver, label) {
   @param {Mixed} The value to resolve
   @since 1.2.0
 */
-export function resolve(result, label) {
+export function resolve(result: unknown, label?: string) {
   return TestPromise.resolve(result, label);
 }
 
@@ -61,11 +72,11 @@ export function getLastPromise() {
 // 1. Set `Ember.Test.lastPromise` to null
 // 2. Invoke method
 // 3. Return the last promise created during method
-function isolate(onFulfillment, result) {
+function isolate<T, TResult = T>(onFulfilled: OnFulfilled<T, TResult>, result: T) {
   // Reset lastPromise for nested helpers
   lastPromise = null;
 
-  let value = onFulfillment(result);
+  let value = onFulfilled(result);
 
   let promise = lastPromise;
   lastPromise = null;
diff --git a/packages/ember-testing/lib/test/run.js b/packages/ember-testing/lib/test/run.ts
similarity index 76%
rename from packages/ember-testing/lib/test/run.js
rename to packages/ember-testing/lib/test/run.ts
index d8bcd0592f4..c9ce6a5603d 100644
--- a/packages/ember-testing/lib/test/run.js
+++ b/packages/ember-testing/lib/test/run.ts
@@ -1,6 +1,6 @@
 import { _getCurrentRunLoop, run as emberRun } from '@ember/runloop';
 
-export default function run(fn) {
+export default function run<T>(fn: () => T): T {
   if (!_getCurrentRunLoop()) {
     return emberRun(fn);
   } else {
diff --git a/packages/ember-testing/lib/test/waiters.js b/packages/ember-testing/lib/test/waiters.ts
similarity index 71%
rename from packages/ember-testing/lib/test/waiters.js
rename to packages/ember-testing/lib/test/waiters.ts
index 12f891a1122..5b53310d976 100644
--- a/packages/ember-testing/lib/test/waiters.js
+++ b/packages/ember-testing/lib/test/waiters.ts
@@ -1,8 +1,8 @@
 /**
  @module @ember/test
 */
-const contexts = [];
-const callbacks = [];
+const contexts: unknown[] = [];
+const callbacks: Array<() => unknown> = [];
 
 /**
    This allows ember-testing to play nicely with other asynchronous
@@ -40,16 +40,27 @@ const callbacks = [];
    @param {Function} callback
    @since 1.2.0
 */
-export function registerWaiter(context, callback) {
-  if (arguments.length === 1) {
-    callback = context;
-    context = null;
+export function registerWaiter<T>(context: T, callback: (this: T) => unknown): void;
+export function registerWaiter(callback: (this: null) => unknown): void;
+export function registerWaiter<T>(
+  ...args: [context: T, callback: (this: T) => unknown] | [callback: (this: null) => unknown]
+): void {
+  let checkedCallback: () => unknown;
+  let checkedContext: T | null;
+
+  if (args.length === 1) {
+    checkedContext = null;
+    checkedCallback = args[0];
+  } else {
+    checkedContext = args[0];
+    checkedCallback = args[1];
   }
-  if (indexOf(context, callback) > -1) {
+
+  if (indexOf(checkedContext, checkedCallback) > -1) {
     return;
   }
-  contexts.push(context);
-  callbacks.push(callback);
+  contexts.push(checkedContext);
+  callbacks.push(checkedCallback);
 }
 
 /**
@@ -64,7 +75,7 @@ export function registerWaiter(context, callback) {
    @param {Function} callback
    @since 1.2.0
 */
-export function unregisterWaiter(context, callback) {
+export function unregisterWaiter(context: unknown, callback: unknown) {
   if (!callbacks.length) {
     return;
   }
@@ -100,14 +111,15 @@ export function checkWaiters() {
   for (let i = 0; i < callbacks.length; i++) {
     let context = contexts[i];
     let callback = callbacks[i];
-    if (!callback.call(context)) {
+    // SAFETY: The loop ensures that this exists
+    if (!callback!.call(context)) {
       return true;
     }
   }
   return false;
 }
 
-function indexOf(context, callback) {
+function indexOf(context: unknown, callback: unknown) {
   for (let i = 0; i < callbacks.length; i++) {
     if (callbacks[i] === callback && contexts[i] === context) {
       return i;

From 09a73ada1e5140ea0f0179dcbe6245255c336674 Mon Sep 17 00:00:00 2001
From: Peter Wagenet <peter.wagenet@gmail.com>
Date: Thu, 12 May 2022 14:51:31 -0700
Subject: [PATCH 2/2] Convert @ember/test to TS

---
 packages/@ember/test/adapter.js             |  3 ---
 packages/@ember/test/adapter.ts             |  3 +++
 packages/@ember/test/{index.js => index.ts} | 11 ++++++-----
 3 files changed, 9 insertions(+), 8 deletions(-)
 delete mode 100644 packages/@ember/test/adapter.js
 create mode 100644 packages/@ember/test/adapter.ts
 rename packages/@ember/test/{index.js => index.ts} (62%)

diff --git a/packages/@ember/test/adapter.js b/packages/@ember/test/adapter.js
deleted file mode 100644
index e0f19949e64..00000000000
--- a/packages/@ember/test/adapter.js
+++ /dev/null
@@ -1,3 +0,0 @@
-import { Test } from 'ember-testing';
-
-export default Test.Adapter;
diff --git a/packages/@ember/test/adapter.ts b/packages/@ember/test/adapter.ts
new file mode 100644
index 00000000000..1832534f0d7
--- /dev/null
+++ b/packages/@ember/test/adapter.ts
@@ -0,0 +1,3 @@
+import { Adapter } from 'ember-testing';
+
+export default Adapter;
diff --git a/packages/@ember/test/index.js b/packages/@ember/test/index.ts
similarity index 62%
rename from packages/@ember/test/index.js
rename to packages/@ember/test/index.ts
index 3f226dbcac6..2cf30f846ce 100644
--- a/packages/@ember/test/index.js
+++ b/packages/@ember/test/index.ts
@@ -1,10 +1,11 @@
 import require, { has } from 'require';
+import { type Test } from 'ember-testing';
 
-export let registerAsyncHelper;
-export let registerHelper;
-export let registerWaiter;
-export let unregisterHelper;
-export let unregisterWaiter;
+export let registerAsyncHelper: typeof Test['registerAsyncHelper'] | (() => never);
+export let registerHelper: typeof Test['registerHelper'] | (() => never);
+export let registerWaiter: typeof Test['registerWaiter'] | (() => never);
+export let unregisterHelper: typeof Test['unregisterHelper'] | (() => never);
+export let unregisterWaiter: typeof Test['unregisterWaiter'] | (() => never);
 
 if (has('ember-testing')) {
   let { Test } = require('ember-testing');