Josh Steadmon <steadmon@xxxxxxxxxx> writes: > In our current testing environment, we spend a significant amount of > effort crafting end-to-end tests for error conditions that could easily > be captured by unit tests (or we simply forgo some hard-to-setup and > rare error conditions).Describe what we hope to accomplish by > implementing unit tests, and explain some open questions and milestones. > Discuss desired features for test frameworks/harnesses, and provide a > preliminary comparison of several different frameworks. > > Signed-off-by: Josh Steadmon <steadmon@xxxxxxxxxx> > Coauthored-by: Calvin Wan <calvinwan@xxxxxxxxxx> > --- The co-author should also signal his acceptance of the D-C-O with his own S-o-b. [*1*] gives a good example. > diff --git a/Documentation/technical/unit-tests.txt b/Documentation/technical/unit-tests.txt > new file mode 100644 > index 0000000000..dac8062a43 > --- /dev/null > +++ b/Documentation/technical/unit-tests.txt > @@ -0,0 +1,141 @@ > += Unit Testing > + > +In our current testing environment, we spend a significant amount of effort > +crafting end-to-end tests for error conditions that could easily be captured by > +unit tests (or we simply forgo some hard-to-setup and rare error conditions). > +Unit tests additionally provide stability to the codebase and can simplify > +debugging through isolation. Writing unit tests in pure C, rather than with our > +current shell/test-tool helper setup, simplifies test setup, simplifies passing > +data around (no shell-isms required), and reduces testing runtime by not > +spawning a separate process for every test invocation. > + > +We believe that a large body of unit tests, living alongside the existing test > +suite, will improve code quality for the Git project. > + > +== Definitions > + > +For the purposes of this document, we'll use *test framework* to refer to > +projects that support writing test cases and running tests within the context > +of a single executable. *Test harness* will refer to projects that manage > +running multiple executables (each of which may contain multiple test cases) and > +aggregating their results. > + > +In reality, these terms are not strictly defined, and many of the projects > +discussed below contain features from both categories. > + OK. > +== Choosing a framework & harness > + > +=== Desired features > + > +==== TAP support > + > +The https://testanything.org/[Test Anything Protocol] is a text-based interface > +that allows tests to communicate with a test harness. It is already used by > +Git's integration test suite. Supporting TAP output is a mandatory feature for > +any prospective test framework. > + > +==== Diagnostic output > + > +When a test case fails, the framework must generate enough diagnostic output to > +help developers find the appropriate test case in source code in order to debug > +the failure. > + > +==== Parallel execution > + > +Ideally, we will build up a significant collection of unit tests cases, most > +likely split across multiple executables. It will be necessary to run these > +tests in parallel to enable fast develop-test-debug cycles. > + > +==== Vendorable or ubiquitous > + > +If possible, we want to avoid forcing Git developers to install new tools just > +to run unit tests. So any prospective frameworks and harnesses must either be > +vendorable (meaning, we can copy their source directly into Git's repository), > +or so ubiquitous that it is reasonable to expect that most developers will have > +the tools installed already. > + > +==== Maintainable / extensible > + > +It is unlikely that any pre-existing project perfectly fits our needs, so any > +project we select will need to be actively maintained and open to accepting > +changes. Alternatively, assuming we are vendoring the source into our repo, it > +must be simple enough that Git developers can feel comfortable making changes as > +needed to our version. > + > +==== Major platform support > + > +At a bare minimum, unit-testing must work on Linux, MacOS, and Windows. > + > +==== Lazy test planning > + > +TAP supports the notion of _test plans_, which communicate which test cases are > +expected to run, or which tests actually ran. This allows test harnesses to > +detect if the TAP output has been truncated, or if some tests were skipped due > +to errors or bugs. > + > +The test framework should handle creating plans at runtime, rather than > +requiring test developers to manually create plans, which leads to both human- > +and merge-errors. > + > +==== Skippable tests > + > +Test authors may wish to skip certain test cases based on runtime circumstances, > +so the framework should support this. > + > +==== Test scheduling / re-running > + > +The test harness scheduling should be configurable so that e.g. developers can > +choose to run slow tests first, or to run only tests that failed in a previous > +run. > + > +==== Mock support > + > +Unit test authors may wish to test code that interacts with objects that may be > +inconvenient to handle in a test (e.g. interacting with a network service). > +Mocking allows test authors to provide a fake implementation of these objects > +for more convenient tests. > + > +==== Signal & exception handling > + > +The test framework must fail gracefully when test cases are themselves buggy or > +when they are interrupted by signals during runtime. > + > +==== Coverage reports > + > +It may be convenient to generate coverage reports when running unit tests > +(although it may be possible to accomplish this regardless of test framework / > +harness support). Good to see evaluation criteria listed. [Reference] *1* https://lore.kernel.org/git/836a5665b7df065811edc678cb8e70004f7b7c49.1683581621.git.me@xxxxxxxxxxxx/
