The Power of Go: Tests

Praise for The Power of Go: Tests....8 Introduction....9 1. Programming with confidence....11 Self-testing code....12 The adventure begins....13 Verifying the test....16 Running tests with go test....18 Using cmp.Diff to compare results....19 New behaviour? New test.....22 Test cases....23 Adding cases one at a time....27 Quelling a panic....29 Refactoring....31 Well, that was easy....33 Sounds good, now what?....35 2. Tools for testing....37 Gos built-in testing facilities....38 Writing and running tests....39 Interpreting test output....42 The magic package: testing functions that dont exist....44 Validating our mental models....46 Concurrent tests with t.Parallel....47 Failures: t.Error and t.Errorf....48 Abandoning the test with t.Fatal....50 Writing debug output with t.Log....52 Test flags: -v and -run....53 Assistants: t.Helper....56 t.TempDir and t.Cleanup....57 Tests are for failing....58 Detecting useless implementations....60 Feeble tests....62 Comparisons: cmp.Equal and cmp.Diff....63 3. Communicating with tests....66 Tests capture intent....66 Test names should be sentences....68 Failures are a message to the future....69 Are we testing all important behaviours?....71 The power of combining tests....73 Reading tests as docs, with gotestdox....76 Definitions: does, not should....79 A sentence is about the right size for a unit....80 Keeping behaviour simple and focused....82 Shallow abstractions: Is this even worth it?....83 Dont worry about long test names....83 Crafting informative failure messages....84 Exercising failure messages....88 Executable examples....89 4. Errors expected....98 Ignoring errors is a mistake....98 Unexpected errors should stop the test....100 Error behaviour is part of your API....103 Simulating errors....107 Testing that an error is not nil....109 String matching on errors is fragile....113 Sentinel errors lose useful information....114 Detecting sentinel errors with errors.Is....117 Wrapping sentinel errors with dynamic information....120 Custom error types and errors.As....123 Conclusions....126 5. Users shouldnt do that....127 Exhaustive testing....127 Constructing effective test inputs....129 User testing....132 Crafting bespoke bug detectors....135 Table tests and subtests....136 Table tests group together similar cases....140 Using dummy names to mark irrelevant test inputs....141 Outsourcing test data to variables or functions....144 Loading test data from files....148 Readers and writers versus files....149 The filesystem abstraction....150 Using t.TempDir for test output with cleanup....151 Managing golden files....151 Dealing with cross-platform line endings....154 What about the inputs you didnt think of?....155 6. Fuzzy thinking....156 Generating random test inputs....157 Randomly permuting a set of known inputs....158 Property-based testing....159 Fuzz testing....161 The fuzz target....164 Running tests in fuzzing mode....165 Failing inputs become static test cases....166 Fuzzing a risky function....168 Adding training data with f.Add....170 A more sophisticated fuzz target....171 Using the fuzzer to detect a panic....174 Detecting more subtle bugs....179 What to do with fuzz-generated test cases....180 Fixing the implementation....182 7. Wandering mutants....185 What is test coverage?....185 Coverage profiling with the go tool....186 Coverage is a signal, not a target....189 Using bebugging to discover feeble tests....192 Detecting unnecessary or unreachable code....194 Automated mutation testing....196 Finding a bug with mutation testing....197 Running go-mutesting....199 Introducing a deliberate bug....201 Interpreting go-mutesting results....203 Revealing a subtle test feebleness....205 Fixing up the function....207 Mutation testing is worth your while....209 8. Testing the untestable....211 Building a walking skeleton....211 The first test....214 Solving big problems....215 Designing with tests....215 Unexported functions....218 Concurrency....220 Concurrency safety....230 Long-running tasks....235 User interaction....238 Command-line interfaces....246 9. Flipping the script....252 Introducing testscript....252 Running programs with exec....255 Interpreting testscript output....257 The testscript language....259 Negating assertions with the ! prefix....260 Passing arguments to programs....263 Testing CLI tools with testscript....264 Checking the test coverage of scripts....270 Comparing output with files using cmp....271 More matching: exists, grep, and -count....273 The txtar format: constructing test data files....275 Supplying input to programs using stdin....278 File operations....281 Differences from shell scripts....283 Comments and phases....284 Conditions....285 Setting environment variables with env....287 Passing values to scripts via environment variables....288 Running programs in background with &....290 The standalone testscript runner....293 Test scripts as issue repros....295 Test scripts as tests....297 Conclusion....299 10. Dependence day....301 Just dont write untestable functions....302 Reduce the scope of the dependency....303 Be suspicious of dependency injection....305 Avoid test-induced damage....307 Chunk behaviour into subcomponents....309 Reassemble the tested chunks....311 Extract and isolate the key logic....313 Isolate by using an adapter....314 Example: a database adapter....316 Fakes, mocks, stubs, doubles, and spies....324 Dont be tempted to write mocks....325 Turn time into data....327 11. Suite smells....336 No tests....336 Legacy code....338 Insufficient tests....341 Ineffective code review....343 Optimistic tests....345 Persnickety tests....351 Over-precise comparisons....355 Too many tests....357 Test frameworks....358 Flaky tests....362 Shared worlds....365 Failing tests....366 Slow tests....367 A fragrant future....370 About this book....371 Cover photo....371 Who wrote this?....371 Feedback....372 Get my free newsletter....372 Free updates to future editions....372 The Deeper Love of Go....373 The Power of Go: Tools....373 Know Go....374 Further reading....374 Credits....375 Acknowledgements....376