@suchipi/match-inline-snapshot

A standalone matchInlineSnapshot function (like Jest's). You can use it in a different test framework, or without a test framework at all.

Usage Example

const { matchInlineSnapshot } = require("@suchipi/match-inline-snapshot");

/* Uncomment the next line to update non-matching snapshots */
// matchInlineSnapshot.config.shouldUpdateOutdated = true;

matchInlineSnapshot(
  `
    something

    mhm
    yeah
  `,
  `
"
    something else

    yeah
  "
`,
); // throws Error or updates self depending on `matchInlineSnapshot.config.shouldUpdateOutdated`

expect package integration

To configure matchInlineSnapshot to work with Jest's expect package, you can use the installExpectIntegration function:

import {
  matchInlineSnapshot,
  installExpectIntegration,
} from "@suchipi/match-inline-snapshot";
import { expect } from "expect";

installExpectIntegration(expect, matchInlineSnapshot);

NOTE: Depending on the version of the "expect" package in use, you may need to modify matchInlineSnapshot.config.callStructures.normal.stackOffset after calling installExpectIntegration. Try it with the default value, and if it doesn't work, try changing it.

For more information on how this works, see the CallStructure heading below.

API Documentation

The @suchipi/match-inline-snapshot module has the following named exports:

matchInlineSnapshot (Function)

The primary function of this library. Behaves the same as Jest's expect(value).toMatchInlineSnapshot(snapshot), except that the call signature is matchInlineSnapshot(value, snapshot).

If the value doesn't match the snapshot, an error will be thrown. To instead update the snapshot, set matchInlineSnapshot.config.shouldUpdateOutdated to true, or temporarily replace the matchInlineSnapshot call with matchInlineSnapshot.u.

For more info about matchInlineSnapshot.config, see the "Config" heading below.

Config (Type)

The TypeScript type of the value matchInlineSnapshot.config, which is the global configuration for this library. The configuration can be changed on-the-fly as needed.

matchInlineSnapshot.config has the following properties:

• shouldUpdateOutdated (boolean, default false): Whether to update inline snapshots instead of throwing an Error. Analogous to Jest's --updateSnapshot/-u option.
• shouldCreateNew (boolean, default true): Whether to create new snapshots when the second argument to matchInlineSnapshot is omitted. You may wish to set this to false in CI.
• isAllowedToChangeSnapshots (boolean, default true): Whether matchInlineSnapshot is allowed to change snapshot content on disk at all, for any reason.
• fsDelegate (object): Object containing filesystem functions which will be used to update snapshots. See "FsDelegate" heading below for more info.
• sourceMaps (object): Object which you can add source maps onto in order to make snapshots work in TypeScript files and etc.
• serializers (Array of Functions): Transforms to pass the input value through in order to arrive at the final snapshot format.
• parserOptions (object): Options for the underlying parser, equivalent-exchange. See here.
• updateScheduling (string): Option which controls when snapshot updates get written back to disk. Can be either "auto" or "manual", and defaults to "auto".
  • When the value is "auto", snapshots will be updated shortly after the matchInlineSnapshot call(s), in a setTimeout(..., 0).
  • When the value is "manual", snapshots won't be updated until you call matchInlineSnapshot.flushUpdates.
• callStructures (object): Option which controls which AST code structures will be targeted by the update system. By default, it looks for code like:

  matchInlineSnapshot(something, somethingElse);

  but you could configure this option to make it instead look for (as an example):

  expect(something).toMatchInlineSnapshot(somethingElse);

  See "CallStructure" heading below for more info.
• indentation (object): Options which control how indentation is interpreted by the library. The following properties are present:
  • tabSize (number): The character width that matchInlineSnapshot should use for tabs, for the purpose of indentation calculations. Defaults to 2.
  • output (string): Whether snapshots should be indented using tabs or spaces. Valid values are "tabs" or "spaces". Defaults to "spaces".

FsDelegate (Type)

The TypeScript type of the value matchInlineSnapshot.config.fsDelegate, which is an object containing synchronous functions which get used by matchInlineSnapshot in order to update snapshot content on disk.

The default value of matchInlineSnapshot.config.fsDelegate uses Node.js's builtin fs module. If you wish, you may replace matchInlineSnapshot.config.fsDelegate with your own FsDelegate.

An FsDelegate has the following functions:

type FsDelegate = {
  /* Used to read source code in order to find inline snapshot calls */
  readFileAsUtf8(filename: string): string;
  /* Used to write back modified source code in order to update inline snapshots */
  writeUtf8ToFile(filename: string, content: string): void;
};

CallStructure (Type)

A TypeScript type used by matchInlineSnapshot.config.callStructures, which is an object containing AST patterns that the system should detect as match-inline-snapshot calls.

matchInlineSnapshot.config.callStructures is an object with two properties, normal and forceUpdate, which are CallStructures describing the AST pattern of a normal matchInlineSnapshot call and a force-update matchInlineSnapshot call, respectively.

If you wrap matchInlineSnapshot calls in a helper function, you can change matchInlineSnapshot.config.callStructures such that the system targets your wrapper function instead of the wrapped matchInlineSnapshot call. The primary use-case for this is integrating matchInlineSnapshot with "expect" or "assert" helpers.

Each CallStructure has the following properties:

export type CallStructure = {
  /**
   * The AST pattern which represents a match-inline-snapshot call.
   *
   * By default, this is:
   *
   * ```json
   * {
   *   type: "CallExpression",
   *   callee: {
   *     type: "Identifier",
   *     name: "matchInlineSnapshot"
   *   }
   * }
   * ```
   *
   * You can change this to make the snapshot update system target a different
   * code pattern.
   */
  astPattern: { [key: string]: any };

  /**
   * The property path to the snapshot node, starting from the
   * configured `astPattern`.
   *
   * By default, this is `["arguments", 1]`.
   *
   * This controls where the snapshot template literal string gets placed.
   */
  snapshotPath: Array<string | number>;

  /**
   * How many call stack frames away the call-structure-to-update is from the
   * actual library `matchInlineSnapshot` call.
   *
   * If you wrap `matchInlineSnapshot` in a helper method, you'll need to
   * increase this number.
   *
   * Defaults to `0` (ie. the call-to-update is the same as the call to the library).
   */
  stackOffset: number;
};

License

MIT