Do you mock all external contractors or do you use their sandbox in tests?

In testing, both approaches are usually combined: mocking external counterparts and using their sandbox, depending on the goals and type of tests.

Mocking external services is convenient for unit tests to isolate the tested code and avoid dependence on external factors (network, service availability, response speed). This allows for quick and stable logic verification.

Using sandbox environments of external counterparts is justified in integration and system tests, where it is important to verify interaction with the real API, but without the risk of damaging real data or causing unwanted actions.

Thus, mocking is used for fast and reliable unit tests, while sandbox is used for more comprehensive integration and behavior testing in real conditions.