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What is the reason behind the assert statement expecting a pattern instead of a string when trying to match text using a regex pattern?

Answer

Understanding Regex Patterns in Assert Statements

When you're using regular expressions (regex) in assert statements, you need to provide a regex pattern, not a string. Why? Because regex is all about pattern matching within strings. It's a powerful tool that lets you define complex patterns to find specific character sequences or validate a string's format.

Here's the thing: if you provide a string instead of a regex pattern, the assert statement will treat it as a literal value. It will look for an exact match in the text, not interpreting any special characters or patterns within the string as regex elements.

So, how do you use regex patterns in assert statements correctly? You need to provide them as either RegExp objects or strings containing valid regex syntax. This way, the assert statement can properly interpret and apply the matching rules defined by the regex pattern.

import { test } from '@playwright/test';

test('regex pattern in assert', async ({ page }) => {
  await page.goto('https://ray.run/');
  const text = await page.textContent('.content');
  assert.match(text, /Playwright/);
});

In this @playwright/test example, the assert statement is expecting a regex pattern (/Playwright/). It will match this pattern with the actual text from the page.

Remember, when using assert statements with regex for matching text, always provide a valid regex pattern. It ensures accurate and flexible matching based on your criteria.

References

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Rayrun is a community for QA engineers. I am constantly looking for new ways to add value to people learning Playwright and other browser automation frameworks. If you have feedback, email luc@ray.run.