pageobjectmodel.md

Page Object Model pattern

This exemplar showcases a Page Object Model pattern. Good use of this pattern will give maximum reuse of components between different tests whilst making the tests simple to read and understand.

What is the Page Object Model pattern?

A Page Object Model (POM) uses dedicated classes to interact with the web pages of a website under test. The test scripts use the POM to drive the application which allows for good code reuse, separation of concerns and easy to read tests.

A test script is only concerned with the high level intentions of the user and so becomes very quick and easy to read and understand.

test.describe('invalid details should prevent form submit', async () => {
    test('missing hero power', async () => {
        await formPage.fillFormWithValidDetailsExceptHeroPower();
        await formPage.expect.toBeUnableToSubmitForm();
    });
});

The page classes are responsible for decoding the user's intentions into interactions with the UI and then performing them on the given page.

async fillFormWithValidDetailsExceptHeroPower(): Promise<void> {
    await this._firstnameFieldLocator.fill("MyFirstName");
    await this._lastnameFieldLocator.fill("MyLastName");
    await this._emailFieldLocator.fill("myemail@email.com");
}

In our implementation, each page class also has a dedicated assertion class which uses the power of Playwright Locator assertions

async toBeUnableToSubmitForm(): Promise<void> {
    await expect(this.formPage._submitButtonFieldLocator).not.toBeEnabled();
}

Page Object Model tips

• A test script should never directly refer to or use a control. This is because a test script should only change if the user journey changes, not if the implementation of the website changes.
• Test scripts should be short - the Page Object Model (POM) classes should contain the complexity of performing actions on the UI
• Locators and Playwright should never be used directly in a test script - these belong in the POM classes.
• POM methods should start with an abstract verb such as complete, set or submit.
• POM methods should not contain control specific intructions such as click or tick.
• Assertion methods should start with to or not.