如果来自不同喷射器的$ q和$ rootScope com，则在角度测试中解决承诺

Question

我对所有有角度的忍者都有一个有趣的问题。你们其中一个人可以解释为什么一个注入器注入的$ rootScope服务无法解决使用来自另一个注入器的$ q服务创建的$ apply / $ digest的承诺。

使用以下打字稿编写的以下测试可以重现这一点：

describe("TestInjection", () => {

    let rootScope1 : angular.IRootScopeService;
    let q1 : angular.IQService;
    let rootScope2 : angular.IRootScopeService;
    let q2 : angular.IQService;

    beforeEach(() => {
        let $injector1 : angular.auto.IInjectorService = angular.injector(["ng"]);
        let $injector2 : angular.auto.IInjectorService = angular.injector(["ng"]);
        // noinspection TsLint

            q1 = $injector1.get("$q");
            q2 = $injector2.get("$q");
            rootScope1 = $injector1.get("$rootScope");
            rootScope2 = $injector2.get("$rootScope");
    });

    describe("with regard injection and promise testing", () => {

        it("promise should be resolved if both services come from the same injector", () => {
            let deferred = q1.defer();
            let value = false;
            deferred.promise.then((v : boolean) => {
                value = v;
            });
            deferred.resolve(true);
            rootScope1.$digest();
            expect(value).toBeTruthy();
        });

        it("promise should be resolved if both services come from different injectors", () => {
            let deferred = q1.defer();
            let value = false;
            deferred.promise.then((v : boolean) => {
                value = v;
            });
            deferred.resolve(true);
            rootScope2.$digest();
            expect(value).toBeTruthy();
        });
    });
});

我很想理解为什么事情会这样。