What is a test (test case)?

A test case is a specific set of conditions, input data, and expected results used to verify the correctness of software.

Each test describes:

• Preconditions — the state of the system before executing the test.
• Input data — what is provided as input.
• Execution steps — the sequence of actions.
• Expected result — what should happen when the system works correctly.

Example of a test for an addition function:

• Preconditions: the function is available for invocation.
• Input data: 2 and 3.
• Steps: call the addition function with these numbers.
• Expected result: return 5.

Tests help identify errors, regressions, and ensure product quality.