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Test strategy comparison

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
Size Small Large
Coverage Immediate Not straight forward
Feedback Immediate Takes long time
Blast radius Isolated Potentially high
Error localization Easier Harder
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