# Frequently Asked Questions

## The world instance isn’t available in my hooks or step definitions.

If you are referencing the world instance (which is bound to `this`) in a step definition or hook, then you cannot use ES6 arrow functions.

Cucumber uses [apply](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply) internally to call your [step definition](./support_files/step_definitions.md) and
[hook](./support_files/hooks.md) functions using the world object as `this`.

Using `apply` [does not work with arrow functions](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions#call_apply_and_bind), so if you need to reference the world, use a regular `function`.

## Why do my definition patterns need to be globally unique instead of unique only within `Given`, `When`, `Then`?

To encourage a ubiquitous, non-ambiguous domain language.
Using the same language to mean different things is basically the definition of ambiguous.
If you have similar `Given` and `Then` patterns, try adding the word “should” to `Then` patterns.

## Why aren't there `BeforeFeature` and `AfterFeature` hooks?

When Cucumber runs your specifications, scenarios are collected and turned into test cases. The features that those scenarios sit within are not considered in the test run - it's all about scenarios, which should be standalone and not depend on any other scenarios. This is why `Before` and `After` hooks are available at the global and scenario levels but not the feature level.

If you find yourself wanting to do some setup work at the feature level, consider whether you can move it to the scenario level and make it idempotent. You can target a hook at all scenarios in a feature [with tags](https://cucumber.io/docs/cucumber/api/?lang=javascript#tags).

## Why am I seeing `The "from" argument must be of type string. Received type undefined`?

See [Invalid installations](./installation.md#invalid-installations)