jest.md

Jest

Jest tests JavaScript.

• Reference
• Install
• Options
• Use
• Snapshots
• //jest:rules.bzl
  • jest_test

Reference

Starlark reference

Install

Add jest as an external dependency.

Options

By default, Jest uses -i --no-cache. Add options via test arguments.

Sharding support requires Jest v28.

Use

example/example.js

export function add(a, b) {
  return a + b;
}

example/example.spec.js

const { add } = require("./example");

test("adds", () => {
  expect(add(1, 2)).toBe(3);
});

example/jest.config.js

exports.verbose = true;

example/BUILD.bzl

load("@better_rules_javascript//commonjs:rules.bzl", "cjs_root")
load("@better_rules_javascript//javascript:rules.bzl", "js_library")
load("@better_rules_javascript//jest:rules.bzl", "jest_test")

cjs_root(
    name = "root",
)

js_library(
    name = "jest_config",
    root = ":root",
    srcs = ["jest.config.js"],
)

js_library(
    name = "lib",
    root = ":root",
    srcs = ["example.js"],
)

jest_test(
    name = "test",
    config = "jest.config.js",
    config_dep = ":jest_config",
    dep = ":test_lib",
    jest = "@npm//jest:lib",
    node = "@better_rules_javascript//rules:nodejs",
)

js_library(
    name = "test_lib",
    root = ":root",
    srcs = ["example.spec.js"],
)

Snapshots

To update snapshots, run the test as an executable with -u/--update-snapshot.

bazel run :example -- -u

//jest:rules.bzl

jest_test

jest_test(name, bash_preamble, config, config_dep, data, dep, env, jest, node, node_options)

ATTRIBUTES

Name	Description	Type	Mandatory	Default
name	A unique name for this target.	Name	required
bash_preamble	-	String	optional	""
config	Path to config file, relative to config_dep root.	String	required
config_dep	Jest config dependency.	Label	required
data	Runtime data.	List of labels	optional	[]
dep	Test dependency.	Label	required
env	Environment variables.	Dictionary: String -> String	optional	{}
jest	Jest dependency.	Label	required
node	-	Label	optional	//nodejs
node_options	Node.js options.	List of strings	optional	[]