如何在Angular 7（或2+）中编写文件上传方法的单元测试

Question

我正在尝试为 angular 7 中的文件上传方法编写单元测试。在测试窗口中出现以下错误。我是角度单元测试的新手。有人可以帮忙，如何添加模拟文件以获得完整的代码覆盖率？

类型错误：无法设置未定义的属性“值”

这是我的单元测试代码（规范文件），

describe('ImportComponent', () => {
    let component: ImportComponent;
    let fixture: ComponentFixture<ImportComponent>;
    let element;

    beforeEach(
        async(() => {
            TestBed.configureTestingModule({
                imports: [ HttpClientModule, RouterTestingModule ],
                declarations: [ ImportComponent ]
            }).compileComponents();
        })
    );

    beforeEach(() => {
        fixture = TestBed.createComponent(ImportComponent);
        component = fixture.componentInstance;
        element = fixture.nativeElement;
        fixture.detectChanges();
    });

    it('should create', () => {
        expect(component).toBeTruthy();
    });

    it('should upload the file', () => {
        component.importFile();
        const inputEl = element.querySelector('#postal_file');
        const fileList = { 0: { name: 'foo', size: 500001 } };
        inputEl.value = {
            target: {
                files: fileList
            }
        };
        inputEl.dispatchEvent(new Event('change'));     
    });
});

组件中的方法

importFile() {
        const inputEl: HTMLInputElement = this.el.nativeElement.querySelector('#postal_file');
        const fileCount: number = inputEl.files.length;
        const formData = new FormData();
        if (fileCount > 0) {
            formData.append(this.postalFileName, inputEl.files.item(0));
            this.postalService.importPostalCodes(formData).subscribe((data) => {
                this.result = data;
            });
        }
    }

和 HTML，

<div class="file-import">
        <form action="" method="post" encType="multipart/form-data">
            <label for="postal_file">Choose File</label>
            <input type="file" name="postal_file" id="postal_file">
            <button type="button" (click)="importFile()">Import</button>
        </form>
    </div>

单元测试没有覆盖下图所示的所有代码，请帮助，如何获得 100% 的代码覆盖率。

代码覆盖率图片

Answer 1

测试文件上传和检查模型值集的简单方法。

.html

<input (change)="onFileSelected()" #fileInput type="file" id="file">

.ts

uploadedFile : any

onFileSelected() {
  const inputNode: any = document.querySelector('#file');
  this.uploadedFile  = inputNode.files[0];
}

规格

it('should detect file input change and set uploadedFile  model', () => {
    const dataTransfer = new DataTransfer()
    dataTransfer.items.add(new File([''], 'test-file.pdf'))

    const inputDebugEl  = fixture.debugElement.query(By.css('input[type=file]'));
    inputDebugEl.nativeElement.files = dataTransfer.files;

    inputDebugEl.nativeElement.dispatchEvent(new InputEvent('change'));

    fixture.detectChanges();

    expect(component.uploadedFile).toBeTruthy()
    expect(component.uploadedFile).toBe('test-file.pdf')
    
});

it('file change event should arrive in handler', () => {
    const element = fixture.nativeElement;
    const input = element.querySelector('#file');
    spyOn(component, 'onFileSelected');
    input.dispatchEvent(new Event('change'));
    fixture.detectChanges();
    expect(component.onFileSelected).toHaveBeenCalled();
});