Selector-test-generator NPM

Test generator for selectors based on reselect library.

Motivation

Writing unit-test for selectors based on reselect library depends on lot of boilerplate code. The sample selector test code looks like this

import state from <path_to_mocked_state>;
import { selector, anotherSelector } from <path_to_selector_folder>;

describe('Application/Selectors', () => {
  it('<selector>', () => {
    const received = selector(state);
    const expected = true;

    expect(received).toEqual(expected);
  });

  it('<anotherSelector>', () => {
    const received = anotherSelector(state);
    const expected = false;

    expect(received).toEqual(expected);
  });
});

The current pattern is repeated for most selectors, it takes a lot of time and demotivates writing simple unit tests, which can be quite a lot on a project.

selector-test-generator is trying to solve this problem by generating a file with jest tests for available selectors.

Using

This is a Node.js module available through the npm registry.

Installation is done using the npm install command:

npm install --save-dev selector-test-generator

or yarn add command:

yarn add --dev selector-test-generator

selector-test-generator ready to use as npm-script

selector-test-generator [selector-path-arg] [...options]

Also selector-test-generator run through npx without installing

npx selector-test-generator [selector-path-arg] [...options]

Options

selector-path-arg - define selector path in which the utility will search for selectors and generate tests. Optional argument, default value - current execution folder.
-s, --state <path> - set the mocked state location. Necessary argument

Features

selector-test-generator recursively walk though all directories starting from the execution folder or directory that is set as selector-path-arg. Then search for files with exported selectors. For exported selectors it creates __test__ folder with tests in current file directory. B

For example, we have a folder with selectors in the root project directory

<project>/
├── dir
│   └── withSelectorNested.js
├── state.js
├── withoutSelector.js
├── withSelector.js
└── withSelectorSecond.js

and after running the script

npx selector-test-generator <project>/ -s <project>/state.js

we get the following result

<project>/
├── dir
│   ├── __test__
│   │   └── withSelectorNested.js
│   └── withSelectorNested.js
├── state.js
├── __test__
│   ├── withSelector.js
│   └── withSelectorSecond.js
├── withoutSelector.js
├── withSelector.js
└── withSelectorSecond.js

of course, your test framework should be configured to search for tests in __test__ folder.

Tests are generated for explicitly and implicitly exported selectors.

For file withSelectors.js

import { createSelector } from 'reselect';

const unusedSelector = createSelector(
  ({ sub }) => sub,
  ({ loading }) => loading,
);

const implicityUsedSelector = createSelector(
  ({ sub }) => sub,
  ({ loading }) => loading,
);

const explicitlyUsedSelector = createSelector(
  ({ sub }) => sub,
  ({ property }) => property,
);

export const explicitlyUsedSelector2 = createSelector(
  ({ sub }) => sub,
  ({ undefinedProperty }) => undefinedProperty,
);

export const implicityUsedSelectorProxy = implicityUsedSelector;

export { explicitlyUsedSelector };

export default createSelector(
  ({ sub }) => sub,
  ({ loading }) => loading,
);

Selectors for which tests will be generated are createSelector, explicitlyUsedSelector, implicityUsedSelector, explicitlyUsedSelector2

Generated test selectors/__test__/withSelectors.js

import {
  explicitlyUsedSelector2,
  implicityUsedSelectorProxy,
  explicitlyUsedSelector,
} from '../withSelector.js';
import createSelector from '../withSelector.js';
import state from '../state.js';

describe('Application/Selectors/withSelector.js', () => {
  it('explicitlyUsedSelector2', () => {
    const received = explicitlyUsedSelector2(state);
    const expected = undefined;

    expect(received).toEqual(expected);
  });

  it('implicityUsedSelectorProxy', () => {
    const received = implicityUsedSelectorProxy(state);
    const expected = true;

    expect(received).toEqual(expected);
  });

  it('explicitlyUsedSelector', () => {
    const received = explicitlyUsedSelector(state);
    const expected = 'property';

    expect(received).toEqual(expected);
  });

  it('createSelector', () => {
    const received = createSelector(state);
    const expected = true;

    expect(received).toEqual(expected);
  });
});