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Why the Initial Test Must Fail

publish date: 2026/06/18 05:45:5.504294 UTC

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In TDD, after writing a test for new functionality, the developer runs the test and expects it to fail. Why is this initial failure important?

It satisfies agile process requirements that mandate at least one failed test per sprint

It confirms the test is actually checking the intended functionality and that the functionality does not already exist

It allows the team to record the defect in the bug tracking system before fixing it

A failing test proves that the testing framework itself is working correctly

Correct Answer

It confirms the test is actually checking the intended functionality and that the functionality does not already exist

Explanation

The initial failure of the test is essential confirmation that the test is correctly checking the intended functionality and that this functionality has not already been implemented elsewhere. If the test passes immediately, it may mean the test is wrong, or the feature already exists. The fail-first rule ensures the test has meaningful content.

Reference

Software Engineering, Ian Sommerville, 10th edition

Quizzes you can take where this question appears

Test-Driven Development - Process and Benefits