test: add tests for module initialization

projects/ngx-lss/src/lib/ngx-local-storage.module.spec.ts

@@ -0,0 +1,81 @@
+import { Component, NgModule } from '@angular/core';
+import { fakeAsync, TestBed, tick } from '@angular/core/testing';
+import { Router, RouterModule } from '@angular/router';
+import { RouterTestingModule } from '@angular/router/testing';
+
+import { NgxLocalStorageModule } from './ngx-local-storage.module';
+import { NgxLocalStorageService } from './ngx-local-storage.service';
+
+@Component({ template: '<router-outlet></router-outlet>' })
+export class DummyRootComponent {}
+
+@Component({ template: '' })
+export class LazyDummyComponent {}
+
+@NgModule({
+  declarations: [],
+  imports: [
+    NgxLocalStorageModule.forRoot(),
+    RouterModule.forChild([{ path: '', pathMatch: 'full', component: LazyDummyComponent }]),
+  ],
+})
+export class LazyDummyModule {}
+
+describe('NgxLocalStorageModule', () => {
+  describe('without `forRoot` call', () => {
+    beforeEach(() => {
+      TestBed.configureTestingModule({
+        imports: [NgxLocalStorageModule],
+      });
+    });
+
+    it('throws an error', () => {
+      expect(() => TestBed.inject(NgxLocalStorageService)).toThrow()
+    });
+  });
+
+  describe('with `forRoot` call', () => {
+    describe('when imported once', () => {
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          imports: [NgxLocalStorageModule.forRoot()],
+        });
+      });
+
+      it('injects service', () => {
+        expect(TestBed.inject(NgxLocalStorageService)).toBeTruthy();
+      });
+    });
+
+    describe('when imported more than once', () => {
+      let router: Router;
+
+      beforeEach(() => {
+        TestBed.configureTestingModule({
+          declarations: [DummyRootComponent],
+          imports: [
+            NgxLocalStorageModule.forRoot(),
+            RouterTestingModule.withRoutes([
+              {
+                path: '',
+                pathMatch: 'full',
+                loadChildren: () => Promise.resolve(LazyDummyModule),
+              },
+            ]),
+          ],
+        });
+
+        router = TestBed.inject(Router);
+      });
+
+      // Using `fakeAsync()` and `tick()` to wait for the router to initialize the lazy module
+      it('throws an error on module initialization', fakeAsync(() => {
+
+        expect(() => {
+          router.initialNavigation();
+          tick();
+        }).toThrowError();
+      }));
+    });
+  });
+});