Mastering Test Fixtures and Data Sharing

In professional software testing, tests rarely exist in isolation. They often require a specific environment: a database connection, a pre-populated cache, a file system state, or a specific configuration. Manually repeating this setup in every test violates the DRY (Don't Repeat Yourself) principle and makes your test suite difficult to maintain.

The fcfTest library solves this problem using Fixtures. Fixtures allow you to define common setup and teardown logic that is automatically executed at different levels of your test hierarchy.

One of the most powerful features of fcfTest is the ability to control when the fixture code runs. This is determined by the am_level argument in the FCF_TEST_BEFORE_DEFINE macro.

Fixtures are not applied to everything by default. You must specify which part of the hierarchy they belong to using selectors (Part, Group, Test). You can use the wildcard symbol "*" to apply a fixture to all elements at a certain level.

• "MyPart", "*", "*" — Applies to everything within "MyPart".
• "*", "MyGroup", "*" — Applies to all tests within "MyGroup", regardless of which Part they belong to.
• "*", "*", "TestName" — Applies only to one specific test.

The most common use case for fixtures is passing data to the tests (e.g., a pointer to a database object). Since fixtures and tests are separate code blocks, fcfTest provides a thread-safe global singleton, state, to facilitate this.

To share data, follow these three steps:

1. In the Fixture (Setup): Store data using data and wrap it in a fcf::NTest::SharedPtrAny using make.
   state().data("key", SharedPtrAny::make<int>(42));
2. In the Test: Retrieve the data using the same key and cast it back to its original type.
   int* val = state().data("key").cast<int>();
3. In the Fixture (Teardown): It is good practice to clean up the data using eraseData to prevent side effects in other tests.
   state().eraseData("key");

The following example demonstrates a complete application where a global fixture sets an app version, a group fixture manages a simulated database connection, and a test retrieves both pieces of data.