Update testing guide for Model

Documentation/Contributors/TestingGuide/README.md

@@ -640,13 +640,12 @@ it("Zooms to longitude, latitude, height", function () {
 
 Here, `spyOn` is used to replace `Camera.flyTo` (prototype function on instances) with a spy. When the Geocoder is used to search for a location, the test expects that `Camera.flyTo` was called with the right arguments.
 
-Spies can also be used on non-prototype functions. Here is an excerpt from [ModelSpec.js](https://github.com/CesiumGS/cesium/blob/main/Specs/Scene/ModelSpec.js):
+Spies can also be used on non-prototype functions. For example,
 
 ```javascript
 it("Applies the right render state", function () {
   spyOn(RenderState, "fromCache").and.callThrough();
-
-  return loadModelJson(texturedBoxModel.gltf).then(function (model) {
+  return loadAndZoomToModel({ gltf: gltfUrl }, scene).then(function (model) {
     const rs = {
       frontFace: WebGLConstants.CCW,
       cull: {
@@ -657,7 +656,6 @@ it("Applies the right render state", function () {
     };
 
     expect(RenderState.fromCache).toHaveBeenCalledWith(rs);
-    primitives.remove(model);
   });
 });
 ```
@@ -672,7 +670,7 @@ Beware of too tightly coupling a test with an implementation; it makes engine co
 
 Sometimes, a test requires sample data, like a CZML file or glTF model, or a service. When possible, we try to procedurally create data or mock a response in the test instead of reading a local file or making an external request. For example, [loadArrayBufferSpec.js](https://github.com/CesiumGS/cesium/blob/main/Specs/Core/loadArrayBufferSpec.js) uses a spy to simulate an XHR response.
 
-When external data can't be avoided, prefer storing a small file in a subdirectory of [Specs/Data](https://github.com/CesiumGS/cesium/tree/main/Specs/Data). Avoid bloating the repo with an unnecessarily large file. Update [LICENSE.md](https://github.com/CesiumGS/cesium/blob/main/LICENSE.md) if the data requires a license or attribution. Include a README file when useful, for example, see [Specs/Data/Models/Box-Textured-Custom](https://github.com/CesiumGS/cesium/tree/main/Specs/Data/Models/Box-Textured-Custom).
+When external data can't be avoided, prefer storing a small file in a subdirectory of [Specs/Data](https://github.com/CesiumGS/cesium/tree/main/Specs/Data). Avoid bloating the repo with an unnecessarily large file. Update [LICENSE.md](https://github.com/CesiumGS/cesium/blob/main/LICENSE.md) if the data requires a license or attribution. Include a README file when useful, for example, see [Specs/Data/Models/GltfLoader/BoomBox](https://github.com/CesiumGS/cesium/tree/main/Specs/Data/Models/GltfLoader/BoomBox).
 
 Make external requests that assume the tests are being used with an Internet connection very sparingly. We anticipate being able to run the tests offline.
 
@@ -682,56 +680,37 @@ Make external requests that assume the tests are being used with an Internet con
 
 For asynchronous testing, Jasmine's `it` function uses a `done` callback. For better integration with CesiumJS's asynchronous patterns, CesiumJS replaces `it` with a function that can return promises.
 
-Here is an excerpt from [ModelSpec.js](https://github.com/CesiumGS/cesium/blob/main/Specs/Scene/ModelSpec.js):
+Here is a simplified example of a test from [ModelSpec.js](https://github.com/CesiumGS/cesium/blob/main/Specs/Scene/Model/ModelSpec.js):
 
 ```javascript
-const texturedBoxUrl = "./Data/Models/Box-Textured/CesiumTexturedBoxTest.gltf";
-const texturedBoxModel;
-
-const cesiumAirUrl = "./Data/Models/CesiumAir/Cesium_Air.gltf";
-const cesiumAirModel;
+const modelUrl = "./Data/Models/PBR/Box/Box.gltf";
 
+let scene;
 beforeAll(function () {
-  const modelPromises = [];
-  modelPromises.push(
-    loadModel(texturedBoxUrl).then(function (model) {
-      texturedBoxModel = model;
-    })
-  );
-  modelPromises.push(
-    loadModel(cesiumAirUrl).then(function (model) {
-      cesiumAirModel = model;
-    })
-  );
-
-  return Promise.all(modelPromises);
+  scene = createScene();
 });
-```
 
-Given a model's url, `loadModel` (detailed below) returns a promise that resolves when a model is loaded. Here, `beforeAll` is used to ensure that two models, stored in suite-scoped variables, `texturedBoxModel` and `cesiumAirModel`, are loaded before any tests are run.
-
-Here is an implementation of `loadModel`:
+afterAll(function () {
+  scene.destroyForSpecs();
+});
 
-```javascript
-function loadModelJson(gltf) {
-  const model = primitives.add(new Model());
-
-  return pollToPromise(
-    function () {
-      // Render scene to progressively load the model
-      scene.renderForSpecs();
-      return model.ready;
-    },
-    { timeout: 10000 }
-  ).then(function () {
-    return model;
+it("renders glTF model", function () {
+  return loadAndZoomToModel({ gltf: modelUrl }, scene).then(function (model) {
+    expect(scene).toRenderAndCall(function (rgba) {
+      expect(rgba[0]).toBeGreaterThan(0);
+      expect(rgba[1]).toBeGreaterThan(0);
+      expect(rgba[2]).toBeGreaterThan(0);
+      expect(rgba[3]).toBe(255);
+    });
   });
-}
+});
 ```
 
-Since loading a model requires asynchronous requests and creating WebGL resources that may be spread over several frames, CesiumJS's `pollToPromise` is used to return a promise that resolves when the model is ready, which occurs by rendering the scene in an implicit loop (hence the name "poll") until `model.ready` is `true` or the `timeout` is reached.
+Given a model's url and other options, [`loadAndZoomToModel`](https://github.com/CesiumGS/cesium/blob/main/Specs/Scene/Model/loadAndZoomToModel.js) loads a model, configures the camera, and returns a promise that resolves when a model's `readyPromise` resolves.
+
+Since loading a model requires asynchronous requests and creating WebGL resources that may be spread over several frames, CesiumJS's [`pollToPromise`](https://github.com/CesiumGS/cesium/blob/main/Specs/pollToPromise.js) is used to return a promise that resolves when the model is ready, which occurs by rendering the scene in an implicit loop (hence the name "poll") until `model.readyPromise` resolves or the `timeout` is reached. `loadAndZoomToModel` uses `pollToPromise` to wait until the model is finished loading.
 
-`pollToPromise` is used in many places where a test needs to wait for an asynchronous event before testing its expectations. Here is an excerpt from [BillboardCollectionSpec.js](https://github.com/CesiumGS/cesium/blob/main/Specs/Scene/BillboardCollectionSpec.js):
+`pollToPromise` is also used in many places where a test needs to wait for an asynchronous event before testing its expectations. Here is an excerpt from [BillboardCollectionSpec.js](https://github.com/CesiumGS/cesium/blob/main/Specs/Scene/BillboardCollectionSpec.js):
 
 ```javascript
 it("can create a billboard using a URL", function () {