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Every script writer knows how tedious it is to update a published plugin. In
addition to the basic functionality, many corner cases (empty line, last line,
etc.) and failures (invalid filename, nomodifiable buffer) need to be tested,
and people use Vim on different platforms (Windows / Linux), UIs (Console /
GUI), with different sets of settings (.vimrc) and other loaded plugins.
There already exist multiple unit test plugins and assertion facilities [1],
which are good for checking invariants and verifying side effect-free
implementation functions, but it is still hard to verify the complete plugin
functionality because custom commands and mappings typically change the buffer
contents, open additional windows, or produce other side effects.

This work aims to show that Vim, together with a shell script driver built
around it, allows to write succinct, fully automated regression test suites
through a combination of these verification methods:
- Comparing buffer contents with a predefined nominal file.
- Matching actual Vim message output with a set of expected messages.
- Running unit tests or assertions inside Vim and evaluating the test results.

With this testing framework, Test-Driven Development can finally be practiced
for Vim plugins, too. If you have existing plugins, just add a couple of basic
test cases for a start. Soon, further updates and modifications can be done
much more rapidly with reduced testing effort, and you can finally tackle that
big refactoring that you've been wanting to do all the time, but were too
afraid of because of the testing effort. The author has been following both
approaches with great success.

- vimUnit (by Staale Flock), vimscript #1125
- tAssert (by Tom Link), vimscript #1730
- VimTAP (by Meikel Brandmeyer), vimscript #2213
- spec.vim (by Tom Link), vimscript #2580
- UT (by Luc Hermitte),
- vim-unittest (by h1mesuke),
- Ultimate Test Utility (by Kevin Biskar), vimscript #4724 is a pure Vimscript
  implementation providing various test grouping and assertion functions.

- robot-vim ( by Matt Margolis allows
  to TDD Vim scripts using Ruby scripts that launch Vim instances, pass text,
  execute commands and then run assertions against the buffer text in Ruby.
- vspec (vimscript #3012) by Kana Natsuno allows to write tests BDD-style with
  custom matchers, and is driven by a small Bash script.
- Vader (vimscript #4832) by Junegunn Choi implements BDD-style testing from
  within Vim via a test script in a custom syntax.

Specify an expected output, e.g. in file 'test001.ok'
    expected output
    and more
    expected output
and/or specify expected messages in file 'test001.msgok'
    /\d\+ lines changed/
use an input file ''
    ExPeCteD OuTpUt
    ExPeCteD OuTpUt
write a short test script 'test001.vim'
    normal! gg3gugu
    write test001.out
call the test runner
    $ runVimTests test001.vim
and the framework invokes the test(s) [suites], compares the actual with the
expected output, checks that the messages match, and prints any failures and a
test summary:
    1 file with 2 tests; 0 skipped, 2 run: 2 OK, 0 failures, 0 errors.

runVimTests implements a testing framework for Vim.

Similar to the tests that are part of Vim's source distribution, each test
consists of a testXXX.vim file which is executed in a a separate Vim instance.
The outcome of a test can be determined by a combination of the following

If a testXXX.ok file is provided, the testXXX.vim should save a testXXX.out
file at the end of its execution. The contents of the testXXX.out test file
must be identical to the provided testXXX.ok file for the test to succeed. The
test can either generate the test output itself, or start by editing a (or similar) file and doing modifications to it.
Use this method to test commands or mappings that modify buffer contents.

If a testXXX.msgok file is provided, the testXXX.vim file should generate Vim
messages (from built-in Vim commands, or via :echo[msg]), which are captured
during test execution in a testXXX.msgout file. The testXXX.msgok file
contains multiple message assertions (separated by empty lines), each of which
is compiled into a Vim regexp and then matched against the captured messages.
Each assertion can match exactly once, and all assertions must match in the
same order in the captured Vim messages. (But there can be additional Vim
messages before, after and in between matches, so that you can omit irrelevant
or platform-specific messages from the testXXX.msgok file.) For details, see
This method can verify that errors are reported correctly. Also use this
method to test commands or mappings that print informational messages.

If a testXXX.tap file exists at the end of a test execution, it is assumed to
represent unit test output in the Test Anything Protocol [2], which is then
parsed and incorporated into the test run. This method allows detailed
verification of custom commands, mappings as well as internal functions; the
entire determination of the test result is done in Vim script. Each TAP unit
test counts as one test, even though all those test results are produced by a
single testXXX.vim file. If a plan announced more or less tests than what was
found in the test output, the test is assumed to be erroneous.
Use this method to test the internal implementation functions, or to verify
things that can be checked easily with Vim script.

web site:,
original implementation:,
TAP protocol for Vim:

A test causes an error if none of these ok-files exist for a test, and no
testXXX.tap file was generated (so actually no verification is possible), or
if the test execution does not produce the corresponding output files.

A test run is started through the "runVimTests.(sh|cmd)" script:
    $ runVimTests [{options}] test001.vim|testsuite.txt|path/to/testdir/ [...]

The tests are specified through these three methods, which can be combined:
- Directly specify the filespec of testXXX.vim test script file(s).
- Specify a directory; all *.vim files inside this directory (except for an
  optional special _setup.vim file) will be used as test scripts.
- A test suite is a text file containing (relative or absolute) filespecs to
  test scripts, directories or other test suites, one filespec per line.
  (Commented lines start with #.)

The script returns 0 if all tests were successful, 1 if any errors or failures
occurred, 2 if it wasn't invoked correctly (i.e. bad or missing command-line
arguments) or prerequisites weren't met, 3 in case of an internal error.

After test execution, a summary is printed like this:
    20 files with 33 tests; 2 skipped, 27 run: 16 OK, 11 failures, 6 errors.
    Tests with skips: test006.vim
    Skipped tests: test007.vim
        2 SKIP (tap): Need 'autochdir' option
    Failed tests: test002.vim test012.vim test014.vim test022.vim test032.vim
    Tests with errors: test003.vim test013.vim test023.vim test033.vim