Snapshot-fixtures NPM

snapshot-fixtures

Snapshot fixtures for node:test.

Installation

npm install snapshot-fixtures

When to use this?

This package exposes a function for creating tests based on a directory containing test fixtures. This is useful if you want to run tests based on a string input and a string output, especially for multiline content.

Usage

Let’s say you have the following project structure:

my-project/
├── fixtures/
│   ├── fixture-1/
│   │   ├── input.txt
│   │   ├── expected-1.txt
│   │   ├── expected-2.txt
│   │   └── options.json
│   └── fixture-2/
│       ├── input.txt
│       ├── expected-1.txt
│       ├── expected-2.txt
│       └── options.js
└── test/
    └── fixtures.test.js

Then src/fixtures.test.js could look like this:

import { fn } from 'my-project'
import { testFixturesDirectory } from 'snapshot-fixtures'

testFixturesDirectory({
  directory: new URL('../fixtures', import.meta.url),
  tests: {
    'expected-1.txt'(file, options) {
      return fn(file, options)
    },

    'expected-2.txt'(file, options) {
      return fn(file, options, 'additional options')
    }
  }
})

This test asserts that the contents of the expected-1.txt and expected-2.txt tests of each fixture match the respective return value of matching test function.

API

`assertEqual(actual, expected[, options])`

Assert two strings are equal.

If the strings are not equal, an assertion error will be thrown. This assertion error contains a pretty diff of the two strings.

Arguments

actual (string) — The actual value that was produced.
expected (string) — The value that was expected.
options (object, optional) — An object with additional options. The following options are supported:
- url (string | URL) — The file URL to include in the assertion error if expected is not equal to actual.

`testFixturesDirectory(options)`

Create a test suite for a fixtures directory based on node:test. A fixtures directory is a directory that contains other directories. For each of these directories a nested test suite is created. For each of these nested test suites, a test is created based on the tests passed. Each test reads the input file, uses the given test function to generate output, and compares it to the content of the expected output file.

Options

directory (string | URL) — The directory containing fixtures as a URL or URL string.
prettier (boolean, optional) — If true, format the generated value with Prettier. (Default: false)
tests (object) — A mapping of test name to a fixture test.
write (boolean) — If true, overwrite the expected content with the actual content. In CI, the output is never written. (Default: false)

`Test`

A test to run, either as a fixture test object, or as a generate function. The generate function takes a VFile as input, which is read from the input file and return a string that should match the expected output. A second argument options can be accepted. This may contain the options of the fixture. These options are read from the options.cjs, options.js, options.json or options.mjs file in the fixture directory.

A test may be an object with the generate and optional input, expected properties. In this case input determines which input file to read, generate serves as the generate function, and expected refers to the expected output file.