> ## Documentation Index
> Fetch the complete documentation index at: https://docs.magnitude.run/llms.txt
> Use this file to discover all available pages before exploring further.

# TestCaseAgent

> Reference for the `agent` object used in Magnitude tests.

The `agent` object is your primary tool for interacting with the browser within a Magnitude test. It's an instance of the `TestCaseAgent` class.

`TestCaseAgent` extends [`BrowserAgent`](/reference/browser-agent) and includes all of its methods, such as `act()`, `nav()`, and `extract()`.

In addition to the inherited methods, `TestCaseAgent` provides the following methods for making assertions:

## `agent.check(description)`

Verifies that a certain condition holds true on the web page based on a natural language description. The AI evaluates the description against the current page state (DOM, visibility, text content).

<RequestExample>
  ```typescript Complete Test Case Example theme={null}
  import { test } from 'magnitude-test';

  test('should create three todos', async (agent) => {
      await agent.act('create three todos');
      await agent.check('three todos exist');
  });
  ```
</RequestExample>

<ParamField path="description" type="string" required>
  A natural language statement describing the expected condition or state to verify.
</ParamField>