expect-puppeteer

Assertion library for Puppeteer.

npm install expect-puppeteer

Usage

Modify your Jest configuration:

{
  "setupFilesAfterEnv": ["expect-puppeteer"]
}

Why do I need it

Writing integration test is very hard, especially when you are testing a Single Page Applications. Data are loaded asynchronously and it is difficult to know exactly when an element will be displayed in the page.

Puppeteer API is great, but it is low level and not designed for integration testing.

This API is designed for integration testing:

• It will wait for element before running an action
• It adds additional feature like matching an element using text

Example

// Does not work if button is not in page
await page.click("button");

// Will try for 500ms to click on "button"
await page.toClick("button");

// Will click the first button with a "My button" text inside
await page.toClick("button", { text: "My button" });

The first element to match will be selected

Example

<div class="outer">
  <div class="inner">some text</div>
</div>

// Will match outer div
await expect(page).toMatchElement("div", { text: "some text" });

// Will match inner div
await expect(page).toMatchElement("div.inner", { text: "some text" });

API

Table of Contents

• toClick
• toDisplayDialog
• toFill
• toFillForm
• toMatchTextContent
• toMatchElement
• toSelect
• toUploadFile

expect(instance).toClick(selector[, options])

Expect an element to be in the page or element, then click on it.

• instance <Page|ElementHandle> Context
• selector <string|MatchSelector> A selector or a MatchSelector to click on.
• options <Object> Optional parameters
  • button <"left"|"right"|"middle"> Defaults to left.
  • clickCount <number> defaults to 1. See UIEvent.detail.
  • delay <number> Time to wait between mousedown and mouseup in milliseconds. Defaults to 0.
  • text <string|RegExp> A text or a RegExp to match in element textContent.

await expect(page).toClick("button", { text: "Home" });
await expect(page).toClick({ type: "xpath", value: "\\a" }, { text: "Click" });

expect(page).toDisplayDialog(block)

Expect block function to trigger a dialog and returns it.

• page <Page> Context
• block <function> A function that should trigger a dialog

const dialog = await expect(page).toDisplayDialog(async () => {
  await expect(page).toClick("button", { text: "Show dialog" });
});

expect(instance).toFill(selector, value[, options])

Expect a control to be in the page or element, then fill it with text.

• instance <Page|ElementHandle> Context
• selector <string> A selector to match field
• value <string> Value to fill
• options <Object> Optional parameters
  • delay <number> delay to pass to the puppeteer element.type API

await expect(page).toFill('input[name="firstName"]', "James");

expect(instance).toFillForm(selector, values[, options])

Expect a form to be in the page or element, then fill its controls.

• instance <Page|ElementHandle> Context
• selector <string> A selector to match form
• values <Object> Values to fill
• options <Object> Optional parameters
  • delay <number> delay to pass to the puppeteer element.type API

await expect(page).toFillForm('form[name="myForm"]', {
  firstName: "James",
  lastName: "Bond",
});

expect(instance).toMatchTextContent(matcher[, options])

Expect a text or a string RegExp to be present in the page or element.

• instance <Page|ElementHandle> Context
• matcher <string|RegExp> A text or a RegExp to match in page
• options <Object> Optional parameters
  • polling <string|number> An interval at which the pageFunction is executed, defaults to raf. If polling is a number, then it is treated as an interval in milliseconds at which the function would be executed. If polling is a string, then it can be one of the following values:
    • raf - to constantly execute pageFunction in requestAnimationFrame callback. This is the tightest polling mode which is suitable to observe styling changes.
    • mutation - to execute pageFunction on every DOM mutation.
  • timeout <number> maximum time to wait for in milliseconds. Defaults to 30000 (30 seconds). Pass 0 to disable timeout. The default value can be changed by using the page.setDefaultTimeout(timeout) method.
  • traverseShadowRoots<boolean> Whether shadow roots should be traversed to find a match.

// Matching using text
await expect(page).toMatchTextContent("Lorem ipsum");
// Matching using RegExp
await expect(page).toMatchTextContent(/lo.*/);

expect(instance).toMatchElement(selector[, options])

Expect an element be present in the page or element.

• instance <Page|ElementHandle> Context
• selector <string> A selector to match element
• options <Object> Optional parameters
  • polling <string|number> An interval at which the pageFunction is executed, defaults to raf. If polling is a number, then it is treated as an interval in milliseconds at which the function would be executed. If polling is a string, then it can be one of the following values:
    • raf - to constantly execute pageFunction in requestAnimationFrame callback. This is the tightest polling mode which is suitable to observe styling changes.
    • mutation - to execute pageFunction on every DOM mutation.
  • timeout <number> maximum time to wait for in milliseconds. Defaults to 30000 (30 seconds). Pass 0 to disable timeout. The default value can be changed by using the page.setDefaultTimeout(timeout) method.
  • text <string|RegExp> A text or a RegExp to match in element textContent.
  • visible <boolean> wait for element to be present in DOM and to be visible, i.e. to not have display: none or visibility: hidden CSS properties. Defaults to false.

// Select a row containing a text
const row = await expect(page).toMatchElement("tr", { text: "My row" });
// Click on the third column link
await expect(row).toClick("td:nth-child(3) a");

expect(instance).toSelect(selector, valueOrText)

Expect a select control to be present in the page or element, then select the specified option.

• instance <Page|ElementHandle> Context
• selector <string> A selector to match select element
• valueOrText <string> Value or text matching option

await expect(page).toSelect('select[name="choices"]', "Choice 1");

expect(instance).toUploadFile(selector, filePath)

Expect a input file control to be present in the page or element, then fill it with a local file.

• instance <Page|ElementHandle> Context
• selector <string> A selector to match input element
• filePath <string> A file path

import { join } from "node:path";

await expect(page).toUploadFile(
  'input[type="file"]',
  join(__dirname, "file.txt"),
);

{type: string, value: string}

An object used as parameter in order to select an element.

• type <"xpath"|"css"> The type of the selector
• value <string> The value of the selector

{type:'css', value:'form[name="myForm"]'}
{type:'xpath', value:'.\\a'}

Configure default options

To configure default options like timeout, expect-puppeteer exposes two methods: getDefaultOptions and setDefaultOptions. You can find available options in Puppeteer page.waitForFunction documentation. Default options are set to: { timeout: 500 }.

import { setDefaultOptions } from "expect-puppeteer";

setDefaultOptions({ timeout: 1000 });