This essay attempts to explain the origins, purpose, and use of def, and does not dictate any particular usage pattern, but may be a good place to get started if you’re interested in automating testing of a documentation or similar resource.
The design of dtf grows out of my experiences with managing and editing a large (multi-hundreds of thousands of words, hundreds of files) documentation resource, and is above all a tool to help facilitate and automate many of the tasks and checks that would otherwise require manual operation and checking.
Nevertheless, the testing model that dtf facilitates may be applicable for other classes of projects, or for organizing and managing larger scale functional or integration test suites.
Part of the challenge of large documentation projects is maintaining resource-wide consistency given the timescales needed to construct documentation, the usage patterns, and the lack of tools to help ensure stylistic consistency or correctness.
There are a number of different kinds of consistency that documentation projects must satisfy: consistency with vocabulary and usage style, consistency with product development, and internal factual and organization consistency. While these consistency problems all require different kinds attention and work, without any kind of automation efforts to ensure consistency would:
These strategies help, but they don’t adapt well to growth of the writing team, the size of a documentation resource, or ongoing product development (i.e. “they don’t scale.”) As a result, over time consistency loosens and it becomes more difficult to maintain the resource and information/knowledge debt accumulates, with all of the same challenges and dangers as technical debt.
For software project having reliable and easy to run test suites helps ease some of this burden. The automated testing can detect interface compatibility problems, unit testing can ensure implementation correctness, and functional/integration tests can ensure that larger systems function as expected.
Typically documentation only has minimal amount of regular testing, which is typically limited to the validation that documentation rendering tools provide. Consistency then, will help documentation projects ensure that:
Fundamentally dtf is just a test runner. The core modules implement a reasonably straightforward system for discovering and running tests written in Python. However, rather than running a large number of distinct tests, and facilitating the implementation of custom tests to validate certain behaviors or conditions, dtf turns the existing paradigm on its side:
each “consistency test” has two components a programmatic implementation that describes the conditions of the test, and a description of the specific context that you want to enforce the condition.
If the test conditions, or the “case,” is the business logic, then the context, or the “test” is the data. Running tests with dtf is a process of applying the business logic to all of the test data.
in general any project will have a small to medium sized collection of different kinds of consistency checks, and a large collection of tests, or situations that enforce that check.
while implementation of a condition may require some programming ability, enforcing an existing test in a new situation should not require any programming ability.
In practice, most case definitions for dtf tests are a couple hundred lives of Python code or less, and tests are YAML files with about half a dozen fields or more depending on the case. While there are no records of the performance of truly huge dtf test suites, the current implementation includes a number of possibilities for running tests in parallel, and all tested performance has been exceptional. These features make the following usage patterns viable:
dtf tests can run regularly as part of the development cycles to prevent regressions. If tests run efficiently, writers can run a test suite regularly to help ensure quality. In this way, the right set of dtf tests can function like acceptance test.
dtf suites are easy to extend by adding new YAML test specifications that enforce existing logic in new situations. If it’s easy to increase coverage, then test suite maintenance incurs more minimal maintenance costs.
dtf conditions and tests can wrap and customize various classes of integration tests and other third party validations. For example, dtf could run commands derived from examples in documentation to ensure that the product doesn’t drift from the documentation in smaller harder to detect ways.
Alternatively you may use dtf tests to wrap per-file or per-directory configuration of natural language analysis tools and process the results of these outputs (e.g. spelling, style and diction.)