toEqual does not work with Blob objects

[darkowic]

🐛 Bug Report

not.toEqual throws assertion error for 2 not equal Blob's instances.

  ● test toEqual

    expect(received).not.toEqual(expected)

    Expected value to not equal:
      {Symbol(impl): {"_buffer": {"data": [116, 0, 101, 0, 115, 0, 116, 0, 49, 0], "type": "Buffer"}, "type": "text/plain", Symbol(wrapper): [Circular]}}
    Received:
      {Symbol(impl): {"_buffer": {"data": [116, 0, 101, 0, 115, 0, 116, 0, 50, 0], "type": "Buffer"}, "type": "text/plain", Symbol(wrapper): [Circular]}}

      12 |   const blob1 = arrayBufferToBlob(str2ab('test2'), 'text/plain');
      13 |   const blob2 = arrayBufferToBlob(str2ab('test1'), 'text/plain');
    > 14 |   expect(blob1).not.toEqual(blob2);
         |                     ^
      15 | });

To Reproduce

The test:

it('test toEqual', () => {
  const blob1 = arrayBufferToBlob(str2ab('test2'), 'text/plain');
  const blob2 = arrayBufferToBlob(str2ab('test1'), 'text/plain');
  expect(blob1).not.toEqual(blob2);
});

You can find arrayBufferToBlob and str2ab implementation in the codesandbox.io snippet below.

I have tried with the new toStrictEqual and I receive the same output.

It is worth to note that before upgrade jest to 23 and babel to 7 (from beta 37) it was working for me. So, looks like a regresion in version 23.

Expected behavior

2 different blobs instances are not eqaul.

Link to repl or repo (highly encouraged)

It's not reproduced in codesandox.io but you can see the code - https://codesandbox.io/s/k07x6zpnm3

Run npx envinfo --preset jest

Paste the results here:

  System:
    OS: Linux 4.13 Ubuntu 18.04.1 LTS (Bionic Beaver)
    CPU: (4) x64 Intel(R) Core(TM) i5-7300HQ CPU @ 2.50GHz
  Binaries:
    Node: 8.12.0 - ~/.virtualenvs/viewer/bin/node
    Yarn: 1.9.4 - /usr/bin/yarn
    npm: 6.4.1 - ~/.virtualenvs/viewer/bin/npm
  npmPackages:
    jest: ^23.6.0 => 23.6.0

My settings

  "jest": {
    "collectCoverageFrom": [
      "**/*.{js,jsx}"
    ],
    "moduleDirectories": [
      "node_modules",
      "src"
    ],
    "coverageDirectory": "./reports/coverage",
    "coverageReporters": [
      "text-summary"
    ],
    "moduleNameMapper": {
      ".*\\.(css|less|styl|scss|sass)$": "<rootDir>/internals/mocks/cssModule.js",
      ".*\\.(jpg|jpeg|png|gif|eot|otf|webp|svg|ttf|woff|woff2|mp4|webm|wav|mp3|m4a|aac|oga)$": "<rootDir>/internals/mocks/image.js",
      "imports-loader?.*": "<rootDir>/internals/mocks/importsLoader.js"
    },
    "testRegex": "tests/.*\\.test\\.jsx?$",
    "setupFiles": [
      "<rootDir>/internals/testing/setup.js"
    ],
    "setupTestFrameworkScriptFile": "<rootDir>/internals/testing/setup-test.js",
    "testEnvironment": "jest-environment-jsdom-global",
    "testPathIgnorePatterns": [
      "node_modules.*",
      "/containers/",
      "/build/"
    ],
    "snapshotSerializers": [
      "enzyme-to-json/serializer"
    ]
  },

[rickhanlonii]

cc @pedrottimark for interest

[matheusPereiraG]

I was able to reproduce this. I would be glad to pick this up. Can someone provide me some guidance on how to fix this?

[rickhanlonii]

@matheuspgINF that would be great! I would start with the matcher code here

[rodrigoramos]

Any updates on this?

[josejulio]

Would be nice to be able to test blobs with jest

[rickhanlonii]

Please feel free to submit a PR for this starting with the code linked above.

[codeinabox]

I wouldn't mind raising a PR for this if it is something that would be welcome in the core Jest code

[jeysal]

I would also like to see this work, but I don't think we can support this in Jest? I believe Blob comes from JSDOM, and they should make sure it doesn't have any visible state differences that equals assertions will notice. Does this also happen with the Node.js assert module?

[codeinabox]

AFAIK Blob is only part of the web API and doesn't seem to be implemented in JSDOM

[jeysal]

Then I'm not sure what this is about, Buffers?

[codeinabox]

Then I'm not sure what this is about, Buffers?

The issue is that you can't simply use === to check that two Blob objects are equal, you need to something like FileReader to read the contents of the Blob and compare that.

[jeysal]

The part that I don't understand is if Blobs do not exist in Node.js or in JSDOM, how do you want to compare objects that do not exist using Jest?

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