Exercism Exercises in Scala
Please see the contributing guide
Scala exercises are run by the scala-test-runner.
It ignores the dependencies listed in the sbt files of the exercises. It's important to add all dependencies necessary to run the exercise to the scala-test-runner's dependencies.
bin/test runs each exercise's tests against its example/exemplar solution:
bin/test # every exercise
bin/test two-fer # a single exercise
bin/test two-fer bob # a few of them
Every exercise is a subproject of this build (see project/Exercises.scala), so all of them are verified in a single sbt session.
Inside the sbt shell the same is available as:
sbt
> exercises/test # every exercise
> two-fer/test # a single exercise
> ~two-fer/test # ... and again on every change
The exercises themselves are never modified: a subproject compiles the exemplar/example solution instead of the stub, and a copy of the tests with the pending markers blanked out.
Both are assembled under target/.
To verify the exercises the way the website does, against the test runner's Docker image, use bin/verify-exercises-in-docker instead.
An exercise's test suite can be generated from the canonical data. A generated suite cannot silently drift away from the spec: CI regenerates it and fails if the committed file differs.
An exercise opts in by adding a Jinja2 template at .meta/template.j2.
bin/generate-tests renders the cases .meta/tests.toml records, skipping those marked include = false and those a later case reimplements.
pip install -r bin/generator/requirements.txt
bin/fetch-configlet
bin/configlet sync --tests # clones problem-specifications; see the note below
bin/generate-tests # regenerate every exercise that has a template
bin/generate-tests darts # just one
bin/generate-tests --check # what CI runs
bin/generate-tests --no-pull # skip refreshing problem-specifications
bin/fetch-configlet only downloads configlet itself.
The problem-specifications clone that bin/generate-tests reads is made by running a configlet command that needs it, such as configlet sync.
Afterwards bin/generate-tests keeps that clone current with git pull unless --no-pull is passed.
Generated suites must not be edited by hand - change the template and regenerate.
To convert an exercise, write .meta/template.j2 and run bin/generate-tests <slug>.
See exercises/practice/leap/.meta/template.j2 for a short one.
Templates get cases, each with input, expected, descriptions, expect_error and expect_error_msg, plus a scala filter that renders a canonical value as Scala source.
The exercise must be in sync with problem-specifications first: the generator refuses to run when .meta/tests.toml is missing canonical cases, because the reimplements links it needs live there.
Note that the canonical data describes behaviour, not an API. Where the track's signature differs from the spec, the template is where that mapping lives.
We welcome pull requests that provide fixes to existing test suites (missing tests, interesting edge cases, improved APIs), as well as new problems.
If you're unsure, then go ahead and open a GitHub issue, and we'll discuss the change.
Please submit changes to a single problem per pull request unless you're submitting a general change across many of the problems (e.g. formatting).
The Scala icon used on Exercism is inspired by the official Scala logo, which is copyright École Polytechnique Fédérale de Lausanne.