I was asked this in an interview, I have always read about what unit tests do, but what do they not do?
Is Unit Testing worth the effort?
Any insights? Thanks!
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3I guess the answer is "They don't test what you don't tell them to test" – BackSlash Aug 10 '17 at 09:29
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related: https://stackoverflow.com/questions/1084336/what-should-not-be-unit-tested https://stackoverflow.com/questions/1316848/unit-testing-what-not-to-test – 463035818_is_not_a_number Aug 10 '17 at 09:30
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@BackSlash Thats what I said, but they expected something else! – LoveMeow Aug 10 '17 at 09:31
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1and thats a dupe but not on SO https://softwareengineering.stackexchange.com/questions/147055/when-is-unit-testing-inappropriate-or-unnecessary – 463035818_is_not_a_number Aug 10 '17 at 09:31
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@tobi303 its not a dupe, my questions asks what can unit test no do, not when they are not needed! – LoveMeow Aug 10 '17 at 09:32
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yep also realized it after writing the comment... – 463035818_is_not_a_number Aug 10 '17 at 09:32
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1They don't test what's not in the scope of a "unit", e.g. interactions with other classes/systems. – QBrute Aug 10 '17 at 09:38
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1And before anybody asks: no - LoveMeow isnt a sock puppet of GhostCat ;-) ... but I have to admit: I like that nickname. – GhostCat Aug 10 '17 at 11:58
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The answer is: *They don't test for (find) **bugs***, Unittests verify *desired behavior*. – Timothy Truckle Aug 11 '17 at 15:45
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"Good" unit tests are meant to test units in isolation. Period.
Thus a "real" unit test will not exercise those dependencies of your class under test - that you decided to "cut out" (using mocking/stubbing).
Of course that means that you do not test assumptions how that 3rd party API will react to your calls for example. Because you mock out that 3rd party API.
GhostCat
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