Mock file upload in unit test controller NestJs

Question

I have a method in nest js controller which takes two arguments looks like below :

@UseGuards(JwtAuthGuard, RolesGuard)
  @Roles(MemberType.OWNER)
  @Post('')
  @UseInterceptors(
    FilesInterceptor('images', 4, {
      storage: fileStorageProductImage,
      fileFilter: fileFilter,
      limits: fileSizeLimit,
    }),
  )
  @UseInterceptors(new MulterInterceptor('images'))
  public async addProduct(
    @Req()
    req: Request,
    @UploadedFiles() files: Express.Multer.File[],
  ) {
  
  //code
  //
  }

And here is my unit test

describe('Unit testing path 1', () => {
      const MemberServiceProvider = {
        provide: MemberService,
        useClass: MemberServiceStub,
      };
      beforeEach(async () => {
        const module: TestingModule = await Test.createTestingModule({
          controllers: [ProductsController],
          providers: [MemberServiceProvider],
        }).compile();
        controller = module.get<ProductsController>(ProductsController);
      });
      //
      const result = controller.addProduct(..., ...);
    });

I currently dont know what to pass into that addProduct method since i dont know how to mock request object and Express.Multer.File[]. Thanks in advance

Answer 1

For anyone who is still looking for the answer. I just figured it how to solve this. First thing first we need to define a method that can be used to read files from our local machine via stream.

const fileToBuffer = (filename) => {
  const readStream = fs.createReadStream(filename);
  const chunks = [];
  return new Promise((resolve, reject) => {
    // Handle any errors while reading
    readStream.on('error', (err) => {
      // handle error

      // File could not be read
      reject(err);
    });

    // Listen for data
    readStream.on('data', (chunk) => {
      chunks.push(chunk);
    });

    // File is done being read
    readStream.on('close', () => {
      // Create a buffer of the image from the stream
      resolve(Buffer.concat(chunks));
    });
  });
};

Then, we call that method inside our unit test

const imageBuffer = (await fileToBuffer(
          __dirname + 'path-to-file',
        )) as Buffer;

In our controller, the uploaded files has Express.Multer.File[] types so we have to make variables that has the same type as above.

const imageFiles: Express.Multer.File[] = [];
const myReadableStreamBuffer = new streamBuffers.ReadableStreamBuffer({
      frequency: 10, // in milliseconds.
      chunkSize: 2048, // in bytes.
});
myReadableStreamBuffer.put(imageBuffer as Buffer);
imageFiles.push({
    buffer: imageBuffer,
    fieldname: 'fieldname-defined-in-@UseInterceptors-decorator',
    originalname: 'original-filename',
    encoding: '7bit',
    mimetype: 'file-mimetyp',
    destination: 'destination-path',
    filename: 'file-name',
    path: 'file-path',
    size: 955578,
    stream: myReadableStreamBuffer,
});

Finally, we can call our addProduct method with newly created imagesFiles variable as arguments.