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Testing
Table of Contents
As the smartparens project evolved we've tried several testing strategies from the initial "freestyle" tests through some formalization back to freestyle back to formalization (sigh). I will describe the current practices and then add a few remarks about the "old style" suits which are still found (and run) in the repository (on the CI), but are discouraged to be added to.
We use ert-runner to run all test suites (old and new).
To run all tests, run
$ cask exec ert-runner
This ensures all dependencies are installed and tests are run in proper environment.
If you have all the dependencies already installed (for example by calling cask install or from previous test runs), you can invoke ert-runner directly by calling
$ cask exec ert-runner
You can use the -p switch to only run specific subset of the tests (matched as regular expression), so
$ cask exec ert-runner -p python
will only run tests related to python.
Tests are organized in the test directory. Tests are added to an "appropriate" thematic test file. When picking the right file, use these simple heuristics:
- each broader feature has its own file: parser, insertion, wrapping, commands...
- tests for specific language features go into their own file (
smartparens-<language>-test.el)
Each test file must end with the suffix -test.el. They are regular elisp files. Tests are defined using ert-deftest. All ert tests start with prefix sp-test. All language-specific tests add the language name afterwards, for example sp-test-python. It is useful to follow this convention so that we can run only language specific tests when we change language specific feature.
We try to write tests with as little magic as possible, only abstracting the most annoying repetitions. So instead of adding endless layers of helpers, try to write the tests as plainly as possible to make it easy to throw them away and update or replace them as the conditions change.
There are two philosophical classes of tests: tests testing specific behaviour and data-driven tests. The former is usually employed to test features for specific language support, the latter for the internals, such as the parser, navigation commands and so on.
Behavioral tests should test one specific behaviour, for examples see smartparens-python-test.el. The name of the test should reflect what is being tested.
Data-driven tests usually look very similar: you feed an input to a function and compare its output with an expected value. Repeat for many input/output data sets to verify broad range of possible executions (boundary cases/regular cases/failure modes etc.). This is more advantageous for testing pure functions (no side effects) where you can't test "behaviour" directly as there is seemingly none.
Internals tests are usually data-driven. These include tests for the various parsers, for pair insertion and wrapping helpers and similar.
Most commands are tested using the sp-test-command macro in smartparens-commands-test.el file. This macro wraps the common pattern of:
- insert string,
- execute a command,
- compare with result string.
These tests are data-driven---we test each command by trying lots of input-output scenarios to make sure it works as expected.
Language setup and overriding of prefix arguments is also supported. It is best to read the existing examples to see how it works.
Finer support for specific languages usually gets one test per feature. If we change how ' pair behaves in python, we add a test for each added/changed behaviour. Each test has a representative name (within reason) to help us located the error.
To simulate typing by the user you can use execute-kbd-macro which takes a keyboard-event spec. In short, if the argument is a string it is inserted as-is, so
(execute-kbd-macro "Hello world")will insert Hello world to the buffer.
If you need to insert special characters such as RET, SPC or chords like C-c q and similar, use kbd and pass these as a string, so
(execute-kbd-macro (kbd "hello C-b C-d"))will first insert hello, then go back a character and deletes a character, leaving the buffer with hell.
Beware as there are comple of gotchas. First, you must specify the entire "event" in one call to execute-kbd-macro if you are testing smartparens post-handlers or other features which trigger on keyboard events. If you spread it to multiple calls things might not get picked up during the simulation as they would otherwise.
Also, if you opt for using kbd be aware that all the literal spaces will be removed during the translation. If you want to print a space you must insert the long form description SPC (that is, a literal space character, the text SPC and a literal space character), so
(execute-kbd-macro (kbd "Hello SPC world"))will insert hello world to the buffer.
See this issue for more context.
All tests are usually best written using the sp-test-with-temp-buffer helper method. It takes two required arguments, initial which is a string to be inserted in a new temporary buffer, and initform which is a form executed before the text is inserted. Then follow arbitrary forms.
There is special syntax available for initial string:
- the point is set to the first occurrence of
|, this character is then removed - the mark is set to the first occurrence of
M, this character is then removed
Tests are always run with case-fold-search set to nil. Before initform is executed, input method is turned off. After initform is executed, smartparens-mode is turned on, the initial text is inserted and point and mark are set. Then the rest of the code is executed.
Inside the body you can execute any code you wish with at least one assertion (see should from ert).
A special version sp-test-with-temp-elisp-buffer is provided which automatically sets up emacs-lisp-mode.
You can add some simple wrappers for data-driven tests where it loops through the input/output pairs and calls some function, or just call the function manually from the ert-deftest as many times as you need. If the helpers aren't absolutely needed, we recommend to avoid them.
Here is an example ert test template (designed for clojure-mode):
(ert-deftest sp-test-somethingsomething-clojure ()
(sp-test-with-temp-buffer "initial buffer content, | is the initial point"
(clojure-mode) ;; initform, could be a `progn'
(your-code-in-a-new-temp-clojure-buffer)
(optionally (insert "|") so you can test the resulting point)
(should (equal (buffer-string) "output | buffer"))))There are some remnants of the old system which can be characterized by lots of magic and abstractions. With time it became clear that such an approach is not ideal for tests: it restricts too much and helps too little. If you find any test which you don't understand right away, chances are you are looking at the "old-style" suites.
Before you start writing your test read the previous section on "new-style" tests. If things still aren't clear, ask someone before you start implementing your tests to save both your and our time. We love questions, so don't worry! This project has a lot of cruft in it and you can't blame yourself for "not getting it" :P
We used ecukes for testing way back when smartparens was simpler, but writing the support code turned out to be more problems than the framework solved. As the tests became unmaintainable we dropped them completely.
We do not accept new ecukes test features anymore.