Helps read and compare files downloaded during a protractor e2e test

protractor-download-helper.ts

// <project_root>/e2e/protractorDownloads/protractor-download-helper.ts

import { browser } from 'protractor';

const fs = require('fs');
const path = require('path');

export class ProtractorDownloadHelper {
  private readonly maxReadWaitTime = 10000; // 10 seconds

  constructor() {
  }

  removeFile(fileName: string): void {
    this.removeFileAtPath(this.getFilePath(fileName));
  }

  async getFileContents(fileName: string): Promise<string> {
    const filePath: string = this.getFilePath(fileName);
    try {
      await browser.driver.wait(() => {
        // Wait until the file exists, download may take some time
        return fs.existsSync(filePath);
      }, this.maxReadWaitTime);
    } catch (err) {
      throw new Error(`File ${filePath} does not exist`);
    }

    return fs.readFileSync(filePath, { encoding: 'utf8' });
  }

  private removeFileAtPath(filePath: string): void {
    if (fs.existsSync(filePath)) {
      fs.unlinkSync(filePath);
    }
  }

  private getFilePath(fileName: string): string {
    return path.join(__dirname, fileName);
  }
}

/*

Sample use:

// <project_root>/e2e/your-test.e2e-spec.ts

import { ProtractorDownloadHelper } from './protractorDownloads/protractor-download-helper';

describe('Your test', () => {

  it('should download proper file', async () => {
    const downloadedFileName = 'download.json';
    const expectedDownloadFileName = 'expected_download.json';

    // Remove the existing download file, if any (so browser doesn't rename the file)
    const downloadHelper: ProtractorDownloadHelper = new ProtractorDownloadHelper();
    downloadHelper.removeFile(downloadedFileName);

    // Click the download button
    $('.download-link').click();

    // Verify file contents
    try {
      const actualFileContents: string = await this.getFileContents(downloadedFileName);
      const expectedFileContents: string = await this.getFileContents(expectedDownloadFileName);
      expect(actualFileContents).toBe(expectedFileContents, 'Downloaded file differs from expected download file');
    } catch (err) {
      fail(`ERROR: Exception thrown: ${err.message}`);
    }

    // Remove file
    downloadHelper.removeFile(downloadedFileName);
  });

});

*/

/*

Sample config:

// <project_root>/protractor.conf.js

const path = require('path');
const downloadsPath = path.resolve(__dirname, './e2e/protractorDownloads');

exports.config = {
  capabilities: {
    browserName: 'chrome',
    chromeOptions: {
      args: [
        '--no-sandbox',
        '--test-type=browser'
      ],
      prefs: {
        download: {
          prompt_for_download: false,
          default_directory: downloadsPath
        }
      }
    }
  },
};

*/

I get "Object is possible 'Undefined'" on this.getFileContents(downloadedFileName);

@mandras73 Do you see this when the code compiles? Or when the code runs?

It it happens at compile time, maybe you have to add some null/undefined checks, e.g.

async getFileContents(fileName: string): Promise<string> {
    if (!browser || !browser.driver || !browser.driver.wait) {
      return null;
    }
    const filePath: string = this.getFilePath(fileName);
    try {
      await browser.driver.wait(() => {
        // Wait until the file exists, download may take some time
        return fs.existsSync(filePath);
      }, this.maxReadWaitTime);
    } catch (err) {
      throw new Error(`File ${filePath} does not exist`);
    }

    return fs.readFileSync(filePath, { encoding: 'utf8' });
  }

There seems to be more info on StackOverflow.

If it happens at runtime, can you determine which line is the culprit? Can you set a breakpoint or add some console.log() statements to see where it fails?

Please let me know if you find a fix and I will update this gist.

hey!
im using webstorm, and when pasted the code into my ts file (using protractor and typescipt) it show immediately that "this" is undefined
(so it happens before runtime, just in the IDE)

Can you please paste a screenshot here? All of the this references in the gist seem fine to me.