Test Case Design

A well-written test case clearly describes what to test, how to test it, and what result to expect — turning testing from a vague activity into a repeatable, verifiable process.

Anatomy of a Test Case

A good test case is specific enough that anyone — not just its original author — could execute it and get a consistent, meaningful result.

• Test ID — a unique identifier for tracking.
• Title — a short, clear summary of what's being tested.
• Preconditions — what must be true before the test starts.
• Steps — the exact actions to perform, in order.
• Expected Result — precisely what should happen if the software is working correctly.
• Actual Result — recorded after execution, to compare against the expected result.

Equivalence Partitioning and Boundary Values

Two powerful techniques help design efficient test cases: equivalence partitioning groups inputs into classes that should behave the same way (testing one representative from each), and boundary value analysis specifically tests the edges of those classes, like a minimum or maximum allowed value, where bugs are disproportionately likely to hide.

Common Mistakes

• Writing vague test steps like "test the login" instead of precise, actionable steps and a specific expected result.
• Forgetting to test boundary values (the smallest and largest valid inputs, and values just outside that range), where off-by-one bugs commonly hide.
• Testing many inputs from the same equivalence class, wasting effort without meaningfully increasing coverage.
• Omitting preconditions, leaving ambiguity about the required starting state before the test can be run correctly.