jest-serializer-ansi-escapes

Jest snapshot serializer for ANSI escape sequences.

This snapshot serializer converts ANSI escape sequences into human readable text. It supports color, style and cursor control escapes and works with vanilla sequences as well as the output from libraries like chalk, colors, ansi-escapes, ansi-styles or terminal-kit.

For example, the following test:

// ansiEscapes.test.js
import { expect, jest, test } from "@jest/globals";
import ansiEscapesSerializer from "jest-serializer-ansi-escapes";

expect.addSnapshotSerializer(ansiEscapesSerializer);

const output = [];

jest
  .spyOn(process.stdout, "write")
  .mockImplementation((chunk) => output.push(chunk));

test("ansi escapes", () => {
  process.stdout.write("\u001b[1;2mLoading...\u001b[0m");
  process.stdout.write("\u001b[2K\u001b[G");
  process.stdout.write("\u001b[3;32mSuccess!\u001b[0m");

  expect(output.join("")).toMatchSnapshot();
});

would output this snapshot:

exports[`ansi escapes 1`] = `
"<bold, dim>Loading...</>
<eraseLine>
<moveCursorToColumn1>
<italic, green>Success!</>"
`;

Install

npm add -D jest-serializer-ansi-escapes

Usage with Jest

You can use expect.addSnapshotSerializer() to enable the serializer for a particular test file:

import { expect } from "@jest/globals";
import ansiEscapesSerializer from "jest-serializer-ansi-escapes";

expect.addSnapshotSerializer(ansiEscapesSerializer);

If you prefer to use it for all tests in a project, add it to the snapshotSerializers list of your Jest configuration:

module.exports = {
  snapshotSerializers: ["jest-serializer-ansi-escapes"],
};

Usage with Pretty Format

A Jest snapshot serializer is a plugin of Pretty Format, hence this serializer can be also used directly with pretty-format library:

import { format as prettyFormat } from "pretty-format";
import ansiEscapesSerializer from "jest-serializer-ansi-escapes";

const sequence = "\u001b[26G";

const formattedSequence = prettyFormat(sequence, {
  plugins: [ansiEscapesSerializer],
});

console.log(formattedSequence); // <moveCursorToColumn26>

Notes

Currently only 16 colors are all supported.

Keep in mind that the escape sequences are not validated. Unrecognized sequence will print as <ESC>[a1b2c3, or as <?> in case this is a color or style sequence.

pretty-ansi — Convert ANSI escape sequences to human readable text.

License

MIT