%% date:: [[2021-02-13]], [[2023-02-22]] %% # [[Testing shows the presence of defects, not their absence]] When a test fails, a defect is found (whether that defect is in the application requirements or in the application code). When a test succeeds, however, that does not indicate the absence of a defect. Test cases are created based on the defects that we know of or can conceive of. Previous testing experience can help us improve the quality of these guesses (by allowing us to turn [[Slow Thinking]] into [[Fast Thinking]]), but it's naïve to think that's sufficient. There will always be defects we don't find because we didn't think to look for them. This is why [[Exploratory testing]] is an integral tool in a tester's toolkit. Exploratory testing assumes there are things we don't know, and seeks to find defects we haven't thought of.