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Can a butterfly flapping its wings cause a tornado somewhere else in the world?

Bug fix → break other code?

[undesirable side effects of modifications] Bug fix → break other code?

[undesirable side effects of modifications] Bug fix → break other code?

[undesirable side effects of modifications] Bug fix → break other code?

Stop butterflies from causing tornadoes: preventing CS2103/T, Lecture 1, Part 3, [Aug 15, 2014]

Stop butterflies from causing tornadoes: preventing CS2103/T, Lecture 1, Part 3, [Aug 15, 2014]

Stop butterflies from causing tornadoes: preventing CS2103/T, Lecture 1, Part 3, [Aug 15, 2014]

TEST CASE Software Under Test (SUT) test input actual output expected output Compare Locate bug modify other test cases Regression testing mismatch = bug located! How to prevent?

TEST CASE Software Under Test (SUT) test input actual output expected output Compare Locate bug modify other test cases Regression testing mismatch = bug located! … is the re-running of existing tests to detect regressions.

TEST CASE Software Under Test (SUT) test input actual output expected output Compare Locate bug modify other test cases Regression test mismatch = bug located!

Software Under Test (SUT) test input mismatch = actual output expected output Compare Debug modify bug located! TEST CASE other test cases Regression test

Software Under Test (SUT) test input mismatch = actual output expected output Compare Debug modify bug located! TEST CASE other test cases Regression test

Software Under Test (SUT) test input mismatch = actual output expected output Compare Debug modify bug located! TEST CASE other test cases Regression test For this to work: 1. Document test cases 2. Automate testing

Example SUT (Text UI Minesweeper)

1. Document test cases scripted testing exploratory testing Test case 1: input: expected: Test case 2: input:

2. Automate testing (for Text UIs) TEST CASE 1 expected output TEST CASE 2 expected output TEST CASE 3 expected output test input

2. Automate testing (for Text UIs) TEST CASE 1 expected output TEST CASE 2 expected output TEST CASE 3 expected output test input

2. Automate testing (for Text UIs) expected output test input

2. Automate testing (for Text UIs) C:\MinesweeperTextUI.exe FC actual.txt expected.txt Comparing files actual.txt and expected.txt FC: no differences encountered C:\MinesweeperTextUI.exe FC actual.txt expected.txt Comparing files actual.txt and expected.txt FC: no differences encountered actual.txt C:\

To prevent ……………….. exploratory or …………..? manual or ……………….?