What is the difference between Use Case, Test Scenario and Test Case?

Use cases, test scenarios, and test cases are all important concepts in software development, but they serve different purposes at different stages of the testing process.

Here's a breakdown to clarify the distinction:

Use Case:

A use case is a specific way a user interacts with the system to achieve a particular goal. It outlines the steps the user takes and the system's responses. Use cases are high-level descriptions. They provide a functional overview but don't specify exact test steps or expected results. Use cases are mainly created by business analysts, product owners, or system designers during the requirements gathering phase. A use case might describe how a customer logs in to an online store, browses for products, adds items to their cart, and completes a purchase.

Test Case:

A test case is the most detailed level. It specifies the exact steps a tester will follow to execute a particular test, the expected results, and any pass or fail criteria. Test cases are very specific, outlining every interaction, input value, and expected outcome for a particular test. Testers create individual test cases based on the test scenarios during the test design stage. A test case within the invalid credit card scenario might involve entering a specific sequence of numbers that fails the validation check, verifying the system displays an appropriate error message, and confirming the purchase is not completed.

Test Scenarios:

A test scenario builds upon the use case, outlining a specific course of action within the use case to be tested. It focuses on a particular user journey or functionality. Test scenarios are more detailed than use cases but less detailed than test cases. They might group together related test cases or outline general steps for achieving a specific objective. Test scenarios are often created by testers based on the use cases during the test planning stage. A test scenario within the purchase use case might focus on testing the behaviour when a customer enters an invalid credit card number during checkout.