# External Dependency, call to

Call to an external dependency is, as it's name explains, an interaction in which a [unit of code](https://blog.fiftywords.co/unit-of-code) **sends** information to an external dependency such as:

- Database
- HTTP API
- RPC
  
```
function additionWithLogging(
  summand: number,
  otherSummand: number,
  logger: ILogger
): number {
  /** Exit point => external dependency call */
  logger.log(`Will add: ${currentValue} + ${summand}`);

  return otherSummand + summand;
}
```

To verify it a [test double](https://blog.fiftywords.co/test-double) is used, in this case a [mock](https://blog.fiftywords.co/mock).

[🇨🇴 Versión en Español](https://blog.cincuentapalabras.co/dependencia-externa-punto-de-salida)