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Version: 14.3

Snapshot testing

jest-preset-angular provides several snapshot serializers to generate clearer and more human-readable snapshot.

info

BY DEFAULT, the preset provides all of the snapshot serializers below.

Snapshot serializers​

Remove html comments (html-comment)​

Allow removing all the comments in the component HTML in snapshot.

Examples:​

  • In Jest config file
jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  //[...]
  snapshotSerializers: ['jest-preset-angular/build/serializers/html-comment'],
  //[...]
};

export default jestConfig;
  • Or in setup test environment file
jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  //[...]
  setupFilesAfterEnv: ['./setup-jest.ts'],
  //[...]
};
setup-jest.ts
import removeHtmlCommentsSerializer from 'jest-preset-angular/build/serializers/html-comment';

expect.addSnapshotSerializer(removeHtmlCommentsSerializer);
  • Or in individual test files
foo.component.spec.ts
import removeHtmlCommentsSerializer from 'jest-preset-angular/build/serializers/html-comment';

expect.addSnapshotSerializer(removeHtmlCommentsSerializer);

it('should work', () => {
  //[...]
});

Display component HTML (ng-snapshot)​

Allow displaying component HTML with data in snapshot.

Parameters​

  • options(optional):
    • omitAllCompAttrs: remove all component DOM attributes
type NgSnapshotOptions = {
  omitAllCompAttrs?: boolean;
};

Examples:​

  • In Jest config
jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  //[...]
  snapshotSerializers: ['jest-preset-angular/build/serializers/ng-snapshot'],
  //[...]
};

export default jestConfig;
  • Or in setup test environment file
jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  //[...]
  setupFilesAfterEnv: ['./setup-jest.ts'],
  //[...]
};
setup-jest.ts
import componentSnapshotSerializer from 'jest-preset-angular/build/serializers/ng-snapshot';

expect.addSnapshotSerializer(componentSnapshotSerializer);
  • Or in individual test files
foo.component.spec.ts
import componentSnapshotSerializer from 'jest-preset-angular/build/serializers/ng-snapshot';

expect.addSnapshotSerializer(componentSnapshotSerializer);

it('should work', () => {
  //[...]
});

With options​

Effective priority

The configured serializers will have affect in this order:

Jest config -> setup files -> test files

The later the higher priority. This means that with the same serializer, the later one will override the configuration of the previous one in the chain.

  • In setup files:
jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  //[...]
  setupFilesAfterEnv: ['./setup-jest.ts'],
  //[...]
};

export default jestConfig;
setup-jest.ts
import componentSnapshotSerializer from 'jest-preset-angular/build/serializers/ng-snapshot';

expect.addSnapshotSerializer({
  print: (val, print, indent, options, colors) =>
    componentSnapshotSerializer.print(
      val,
      print,
      indent,
      {
        ...options,
        omitAllCompAttrs: true,
      },
      colors,
    ),
  test: componentSnapshotSerializer.test,
});
  • or in individual test files:
foo.component.spec.ts
import componentSnapshotSerializer from 'jest-preset-angular/build/serializers/ng-snapshot';

expect.addSnapshotSerializer({
  print: (val, print, indent, options, colors) =>
    componentSnapshotSerializer.print(
      val,
      print,
      indent,
      {
        ...options,
        omitAllCompAttrs: true,
      },
      colors,
    ),
  test: componentSnapshotSerializer.test,
});

it('should work', () => {
  //[...]
});

Remove Angular attributes (no-ng-attributes)​

Allow removing attributes generated by Angular fixture, like ng-reflect-*, ng-version="*", _ngcontent-c* etc., from component snapshot

Examples:​

  • In Jest config
jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  //[...]
  snapshotSerializers: ['jest-preset-angular/build/serializers/no-ng-attributes'],
  //[...]
};

export default jestConfig;
  • Or in setup test environment file
jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  //[...]
  setupFilesAfterEnv: ['./setup-jest.ts'],
  //[...]
};
setup-jest.ts
import removeNgAttributes from 'jest-preset-angular/build/serializers/no-ng-attributes';

expect.addSnapshotSerializer(removeNgAttributes);
  • Or in individual test files
foo.component.spec.ts
import removeNgAttributes from 'jest-preset-angular/build/serializers/no-ng-attributes';

expect.addSnapshotSerializer(removeNgAttributes);

it('should work', () => {
  //[...]
});