{"id":95,"date":"2026-02-26T00:35:54","date_gmt":"2026-02-26T00:35:54","guid":{"rendered":"https:\/\/sites.nd.edu\/softwaretesting\/?page_id=95"},"modified":"2026-02-26T14:00:01","modified_gmt":"2026-02-26T14:00:01","slug":"unit-testing","status":"publish","type":"page","link":"https:\/\/sites.nd.edu\/softwaretesting\/testing-types\/unit-testing\/","title":{"rendered":"Unit Testing"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

What Is Unit Testing?<\/strong><\/em><\/h2>\n\n\n\n

Unit testing<\/strong> is the practice of testing the smallest testable parts of a software system, such as individual functions, methods, or classes, to verify that each works correctly in isolation.<\/p>\n\n\n\n

A unit<\/em> is typically a single piece of logic with a clear input and output. Unit tests confirm that this logic behaves as expected under normal conditions, edge cases, and error scenarios.<\/p>\n\n\n\n

    <\/ul>\n\n\n\n\n\n\n\t\n\n\t
    Why It Matters<\/th>Who Performs It<\/th>When It Occurs<\/th>\n<\/tr>\n<\/thead>\n
    • Detects defects early<\/strong>, when they are cheapest to fix<\/li>
    • Improves code quality and design<\/li>
    • Makes refactoring safer<\/li>
    • Provides fast feedback during development<\/li>
    • Reduces defects that reach later testing stages<\/li><\/ul><\/td>
    • Software Developers<\/li>
    • Sometimes supported by automated testing as part of CI\/CD pipelines<\/li><\/ul><\/td>
    • During the development (coding) phase<\/strong><\/li>
    • Before integration, system, or user acceptance testing<\/li>
    • Re-run whenever code changes are made<\/li><\/ul><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n\n\n\n\n

      Typical Unit Testing Techniques<\/strong><\/em><\/h2>\n\n\n\n
        <\/ul>\n\n\n\n
          \n
        1. White-Box Testing<\/strong>\n
            \n
          • Tests are designed with full knowledge of the internal code structure.<\/li>\n\n\n\n
          • Purpose<\/em>:<\/em><\/strong> Ensure all logical paths and conditions are exercised.<\/li>\n\n\n\n
          • Techniques include:<\/em>\n
              \n
            • Statement coverage<\/li>\n\n\n\n
            • Branch coverage<\/li>\n\n\n\n
            • Path coverage<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n
            • Equivalence Partitioning<\/strong>\n
                \n
              • Input data is divided into valid and invalid groups (partitions), and one value from each group is tested.<\/li>\n\n\n\n
              • Purpose<\/em>: Reduce the number of test cases while maintaining coverage.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
              • Boundary Value Analysis<\/strong>\n
                  \n
                • Focuses on values at the edges of acceptable input ranges.<\/li>\n\n\n\n
                • Purpose<\/em>: Catch defects that often occur at limits (e.g., minimums and maximums).<\/li>\n<\/ul>\n<\/li>\n\n\n\n
                • Error Handling & Exception Testing<\/strong>\n
                    \n
                  • Verifies how the unit behaves when invalid data, exceptions, or failures occur.<\/li>\n\n\n\n
                  • Purpose<\/em>: Ensure graceful handling of errors and predictable system behavior.<\/li>\n<\/ul>\n<\/li>\n\n\n\n
                  • Mocking and Stubbing<\/strong>\n
                      \n
                    • External dependencies (databases, APIs, services) are replaced with simulated objects.<\/li>\n\n\n\n
                    • Purpose<\/em>: Allow the unit to be tested in isolation, without relying on other components.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n

                      Key Takeaways<\/em><\/strong><\/h2>\n\n\n\n
                        \n
                      1. Unit testing ensures individual pieces of code work correctly before they are combined into a complete system.<\/li>\n\n\n\n
                      2. Strong unit testing dramatically reduces downstream defects and creates a stable foundation for all other testing activities.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

                        What Is Unit Testing? Unit testing is the practice of testing the smallest testable parts of a software system, such as individual functions, methods, or classes, to verify that each works correctly in isolation. A unit is typically a single piece of logic with a clear input and output. Unit tests confirm that this logic […]<\/p>\n","protected":false},"author":4975,"featured_media":0,"parent":43,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-95","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/pages\/95","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/users\/4975"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/comments?post=95"}],"version-history":[{"count":17,"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/pages\/95\/revisions"}],"predecessor-version":[{"id":160,"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/pages\/95\/revisions\/160"}],"up":[{"embeddable":true,"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/pages\/43"}],"wp:attachment":[{"href":"https:\/\/sites.nd.edu\/softwaretesting\/wp-json\/wp\/v2\/media?parent=95"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}