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

# Advanced Tests

### Resp Object

You probably want to make assertions on things other than the response status!
The entire response object looks like this:

```json JSON theme={null}
{
    data: "...",
    status: 200,
    statusText: "OK",
    headers: {
        "content-type": "application/json",
        ...
    }
}
```

### Complex Assertions

If you want to write more complex assertions you can use Javascript expressions
instead of specifying a `key` and a `value`. If the expression resolves to a
truthy value the assertion will pass, otherwise it will fail.

```yaml YAML theme={null}
test:
  - request:
      method: GET
      url: https://example.com
    assert:
      - type: JS
        value: resp.status < 300
```

### Environment Variables

You can specify environment variables in your test file to reuse values across
your test. In this example we make an environment variable called `CREDENTIALS`.
It can then be used anywhere in the test by using the string `{{CREDENTIALS}}`.

```YAML theme={null}
env:
  - name: CREDENTIALS
    value: ...

test:
  - request:
      method: GET
      url: https://example.com
      headers:
        - name: Authorization
          value: '{{CREDENTIALS}}'
    assert:
      - type: JS
        value: resp.status < 300
```

### Extractors

Instead of specifying an environment variable at the top level, you might want
to dynamically create environment variables in each step of the test. You can do
this with extractors.

```yaml YAML theme={null}
env:
  - name: CREDENTIALS
    value: ...

test:
  - request:
      method: GET
      url: https://example.com
      headers:
        - name: Authorization
          value: "{{CREDENTIALS}}"
    extract:
      - name: example_data
        value: resp.data
    assert:
      - type: JS
        value: resp.status < 300
  - request:
      method: POST
      url: https://example.com
      data: "{{example_data}}"
      headers:
        - name: Authorization
          value: "{{CREDENTIALS}}"
    assert:
      - type: JS
        value: resp.status < 300
```