@90poe/jest-performant-warnings-stats-reporter

This is a custom jest reporter that recursively collects all warnings while tests run and notifying user afterwards improving performance.

Motivation

We had problems with:

1. Slow tests run on CI even with silent mode
2. When running tests locally noise in the terminal slows tests enormously

List of superpowers

• more performant than default one (check benchmark)
• can provide statistics on warnings for every test suite (see example)
• can show slowest tests (see example)

Installation

yarn add @90poe/jest-performant-warnings-stats-reporter --dev

or

npm install @90poe/jest-performant-warnings-stats-reporter --save-dev

Usage

In your jest config add the following entry:

{
  reporters: [
        [
            '@90poe/jest-performant-warnings-stats-reporter',
            {
                showSlowest: false,
                maxSlowTests: 5,
                warnOnSlowerThan: 1000,
                showWarningSummary: false,
                warningsConfig: [
                    {
                        name: 'act(...) warnings',
                        regex: /act(...)/im,
                    },
                    {
                        name: 'React Key Issues',
                        regex: /Encountered two children with the same key/im,
                    },
                    // ...
                ],
            },
        ],
    ],
}

Configuration

@90poe/jest-performant-warnings-stats-reporter configuration is based on Jest, available options are shown below.

Option	Description	type	Default value
showSlowest	true / false flag whether to show slowest tests or not	boolean	false
maxSlowTests	quantity of slowest tests to show, dependant on showSlowest flag	number	5
warnOnSlowerThan	a limit in milliseconds, used to identify slow tests	number	400
showWarningSummary	true / false flag whether to show detailed information on warnings	boolean	false
warningsConfig	an array of objects with name and regexp props, where name is title for a warning and regexp is regular expression used to match the console warning. Dependant on showWarningSummary flag	Array<{ name: string, regexp: RegExp }>	[]

Sample of output for different configurations

showSlowest: true

showWarningSummary: false

showWarningSummary: true

Benchmarks

Using hyperfine for running 130 test suites in real world project, we can see advantage in performance comparing with:

• default reporter (up to 20% improvement possible, varies by the number of warnings that exist)
• default reporter with silent mode on (up to 5% improvement)

default jest reporter

default jest reporter with silent mode on

@90poe/jest-performant-warnings-stats-reporter

Contribution

Document

Code of conduct

Document

Licence

MIT