If E2E regression is important, Unit testing is critical for ensure the quality of software. Don’t wait to do it later. Test first!
|Characteristics||Unit tests||E2E tests|
|Focus||Unit of behaviour||A system flow|
|Coverage||Immediate||Not straight forward|
|Feedback||Immediate||Takes long time|
|Blast radius||Isolated||Potentially high|
|Maintainability||Easy||Hard to maintain|
Focus: Unit tests focus on an isolated unit of behaviour, while E2E tests target an integrated system flow that may involve multiple components.
Size: Unit tests focus on specific behaviors, thus being small in size. In contrast, E2E tests vary in size depending on the flow and number of coordinating components.
Coverage: With each unit test, your code coverage could improve immediately. Coverage with E2E is not straight forward and may require additional tooling.
Feedback: Unit tests provide instant feedback, running quickly. In contrast, end-to-end (E2E) tests can take hours due to their integrated nature and complexity.
Blast radius: Unit test failures are isolated and do not affect other tests. Conversely, in end-to-end (E2E) tests, a single step failure can cause the entire suite to fail.
Error localization: Unit tests’ smaller scope makes identifying failure reasons easier, while complex E2E tests may prolong issue identification
Maintainability: Unit tests are easily modifiable, whereas E2E tests demand substantial effort