Zig std.testing: No Built‑in Mocking for Integration Tests Without Production Credentials

When writing integration tests that exercise external services, the primary goal is to run those tests without exposing or requiring real production credentials. The Zig language offers std.testing and test blocks that are executed via zig test, but the standard library does not provide a built‑in mocking framework or fixture support to replace external dependencies during test runs.

Current constraints include the absence of per‑suite setup hooks, no official package registry, and the need for users to manage credential isolation manually. Integration tests are typically implemented as separate executables defined in build.zig, leaving the responsibility for mocking, credential handling, and test isolation to the developer.

The unresolved decision is how best to structure a Zig project so that integration tests can be executed safely with mock or test credentials, while still leveraging std.testing for test discovery and reporting. This involves determining whether Zig provides any documented mechanism for injecting test‑only implementations, or whether the solution must rely on build‑time switches and manual code patterns.

Is there a documented way to inject mock implementations or test credentials during test execution, similar to test hooks in other languages?
Can build steps in build.zig be configured to produce a separate test‑only binary that omits production credentials and includes mock modules, and is this approach officially supported?
What is the recommended method to document and enforce credential isolation for integration tests in Zig projects, especially regarding build flags, environment variables, and interaction with std.testing's filtering and exit behavior?