为什么我的Firebase Firestore安全规则允许对现有文档进行.set（）操作，但是.set（）缺少字段

这是我对stackoverflow提出的第一个问题，所以请让我知道我是否缺少该问题的某些方面，这是优选的还是必需的。

我的目标是了解当创建的文档缺少下面列出的Firestore规则要求的字段时，为什么下面显示的Mocha测试通过了。

摩卡测试代码（请注意，项目ID已检查且正在运行，但此处省略）

const assert = require("assert");
const firebase = require("@firebase/rules-unit-testing");
const { firestore } = require("firebase-admin");
const { debug } = require("console");

const MY_PROJECT_ID = "####";

const myID = "user_abc";
const theirID = "user_def";

const myAuth = {uid: myID, email: "[email protected]"};
const theirAuth = {uid: theirID};

function getFirestore(auth) {
    return firebase.initializeTestApp({projectId: MY_PROJECT_ID, auth: auth}).firestore();
}


function getAdminFirestore() {
    return firebase.initializeAdminApp({projectId: MY_PROJECT_ID}).firestore();
}


beforeEach(async ()=>{
    await firebase.clearFirestoreData({projectId:MY_PROJECT_ID});
});


describe("Our Social App", () => {

    it("Can overwrite an existing post with allowed fields", async()=>{
        const postPath = "/posts/post_123";
        const admin = getAdminFirestore();
        await admin.doc(postPath).set({authorID:myID, content:"content", 
                                       visibility:"private",
                                       headline:"headline"});

        const db = getFirestore(myAuth);
        const docRef = db.doc(postPath);
        await firebase.assertSucceeds(docRef.set({}));
    });

});

after(async ()=>{
    await firebase.clearFirestoreData({projectId:MY_PROJECT_ID});
});

消防站规则

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {

    function documentFieldsCheckOut(requiredFields, allowedFields){
      let requiredAndAllowed = requiredFields.concat(allowedFields);
      return request.resource.data.keys().hasAll(requiredFields) &&
             request.resource.data.keys().hasOnly(requiredAndAllowed);
    }

    function updateHasOnlyAllowedFields(allowedFields){
      return debug(request.resource.data.keys()).hasOnly(allowedFields);
    }

    match /{document=**} {
      allow read, write: if false;
    }

    match /posts/{postID} {
   
      allow update: if ((resource.data.authorID == request.auth.uid) || userIsModerator()) 
                        && updateHasOnlyAllowedFields(["visibility", "content"]);
      
      allow create: if (request.resource.data.authorID == request.auth.uid) &&
                        documentFieldsCheckOut(["authorID", "content", "visibility", "headline"], 
                                                ["photo", "location", "tags"]);
    }

 }
}

注意：注释掉await admin.doc(postPath).set({authorID:myID, content:"content", visibility:"private", headline:"headline"});会导致测试按预期失败。
此外，将.set更改为.updateawait firebase.assertSucceeds(docRef.set({}));也会导致测试按预期失败。