lesson
A fix should not reopen an old defect
1 · Learn
A regression test captures behaviour that must keep working after changes. Start from a reproducible failure, state the expected result and retain the test after fixing the cause. A test that never exercises the failed path gives weak protection.
Tests have scope. A local function test does not prove a deployed database, network or browser workflow works; combine appropriate levels of evidence.
2 · Worked example
If a last-item deletion broke a list view, a regression should delete the final item in an isolated test and verify the empty state, not merely check the page title.
3 · Your turn
Does a passing arithmetic unit test prove that a live save button stores results correctly?
Check your answer
No. The save workflow and its dependencies need their own checks.
4 · Apply your learning
Write a test description for a previously observed boundary defect and specify what the test does not prove.
Adult guidance and safety
Work in an approved local sandbox with invented records and test accounts. Do not access other people's systems or collect real credentials. Practical project evidence is required in addition to these explanations; this is not a specified GCSE Computer Science course.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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