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I use Vader to test Vimscript.

Vader test cases

Vader result


Use your favorite plugin manager.

  • vim-plug
    1. Add Plug 'junegunn/vader.vim' to .vimrc
    2. Run :PlugInstall

Running Vader tests

  • Vader [file glob ...]
  • Vader! [file glob ...]
    • Exit Vim after running the tests with exit status of 0 or 1
      • vim '+Vader!*' && echo Success || echo Failure
        • (You need to pass --nofork option when using GVim)
    • If the description of Do or Execute block includes FIXME or TODO, the block is recognized as a pending test case and does not affect the exit status.
    • If the environment variable VADER_OUTPUT_FILE is set, the test results will be written to it as well, otherwise they are written to stderr using different methods (depending on Neovim/Vim).

Syntax of .vader file

A Vader file is a flat sequence of blocks each of which starts with the block label, such as Execute:, followed by the content of the block indented by 2 spaces.

  • Given
    • Content to fill the execution buffer
  • Do
    • Normal-mode keystrokes that can span multiple lines
  • Execute
    • Vimscript to execute
  • Then
    • Vimscript to run after Do or Execute block. Used for assertions.
  • Expect
    • Expected result of the preceding Do/Execute block
  • Before
    • Vimscript to run before each test case
  • After
    • Vimscript to run after each test case

If you want to skip 2-space indention, end the block label with a semi-colon instead of a colon.

Basic blocks


The content of a Given block is pasted into the "workbench buffer" for the subsequent Do/Execute blocks. If filetype parameter is given, &filetype of the buffer is set accordingly. It is also used to syntax-highlight the block in .vader file.

Given [filetype] [(comment)]:
  [input text]


The content of a Do block is a sequence of normal-mode keystrokes that can freely span multiple lines. A special key can be written in its name surrounded by angle brackets preceded by a backslash (e.g. \<Enter>).

Do block can be followed by an optional Expect block.

Do [(comment)]:


The content of an Execute block is plain Vimscript to be executed.

Execute block can also be followed by an optional Expect block.

Execute [(comment)]:

In Execute block, the following commands are provided.

  • Assertions
    • Assert <boolean expr>[, message]
    • AssertEqual <expected>, <got>[, message]
    • AssertNotEqual <unexpected>, <got>[, message]
    • AssertThrows <command>
      • This will set g:vader_exception (from v:exception) and g:vader_throwpoint (from v:throwpoint).
  • Other commands
    • Log "Message"
    • Save <name>[, ...]
    • Restore [<name>, ...]

The following syntax helper functions are provided:

  • SyntaxAt: return a string with the name of the syntax group at the following position:

    • SyntaxAt(): current cursor position
    • SyntaxAt(col): current cursor line, at given column
    • SyntaxAt(lnum, col): line and column
  • SyntaxOf(pattern[, nth=1]): return a string with the name of the syntax group at the first character of the nth match of the given pattern. Return '' if there was no match.

The path of the current .vader file can be accessed via g:vader_file.

In addition to plain Vimscript, you can also test Ruby/Python/Perl/Lua interface with Execute block as follows:

Execute [lang] [(comment)]:
  [<lang> code]

See Ruby and Python examples here.


A Then block containing Vimscript can follow a Do or an Execute block. Mostly used for assertions. Can be used in conjunction with an Expect block.

Then [(comment)]:


If an Expect block follows an Execute block or a Do block, the result of the preceding block is compared to the content of the Expect block. Comparison is case-sensitive. filetype parameter is used to syntax-highlight the block.

Expect [filetype] [(comment)]:
  [expected output]



The content of a Before block is executed before every following Do/Execute block.

Before [(comment)]:
  [vim script]


The content of an After block is executed after every following Do/Execute block.

After [(comment)]:
  [vim script]



You can include other vader files using Include macro.

Include: setup.vader

# ...

Include: cleanup.vader


Any line that starts with #, ", =, -, ~, ^, or * without indentation is considered to be a comment and simply ignored.

# Typical comment #

Given (fixture):

Do (modification):
* change inner word
* to

Expect (result):


# Test case
Execute (test assertion):
  Assert 1 == line('$')

  setf python
  AssertEqual 'python', &filetype

Given ruby (some ruby code):
  def a
    a = 1

Do (indent the block):

Expect ruby (indented block):
  def a
    a = 1

Do (indent and shift):

Expect ruby (indented and shifted):
    def a
      a = 1

Given c (C file):
  int i = 0;

Execute (syntax is good):
  AssertEqual SyntaxAt(2), 'cType'
  AssertEqual SyntaxOf('0'), 'cNumber'

Setting up isolated testing environment

When you test a plugin, it's generally a good idea to setup a testing environment that is isolated from the other plugins and settings irrelevant to the test. The simplest way to achieve this is to start Vim with a mini .vimrc as follows:

vim -Nu <(cat << EOF
filetype off
set rtp+=~/.vim/bundle/vader.vim
set rtp+=~/.vim/bundle/vim-markdown
set rtp+=~/.vim/bundle/vim-markdown/after
filetype plugin indent on
syntax enable
EOF) +Vader*

Travis CI integration

To make your project tested on Travis CI, you need to add .travis.yml to your project root. For most plugins the following example should suffice.

language: vim

before_script: |
  git clone

script: |
  vim -Nu <(cat << VIMRC
  filetype off
  set rtp+=vader.vim
  set rtp+=.
  set rtp+=after
  filetype plugin indent on
  syntax enable
  VIMRC) -c 'Vader! test/*' > /dev/null

(Note that vim is not a valid language for Travis CI. It just sets up Ruby execution environment instead as the default.)


Projects using Vader

See the wiki page.

Known issues

feedkeys() cannot be tested

The keystrokes given to the feedkeys() function are consumed only after Vader finishes executing the content of the Do/Execute block. Take the following case as an example:

Do (Test feedkeys() function):
  \<C-O>:call feedkeys('456')\<CR>

Expect (Wrong!):

You may have expected 123456789, but the result is 123789456. Unfortunately I have yet to find a workaround for this problem. Please let me know if you find one.

Some events may not be triggered

It is reported that CursorMoved event is not triggered inside a Do block. If you need to test a feature that involves autocommands on CursorMoved event, you have to manually invoke it in the middle of the block using :doautocmd.

Do (Using doautocmd):
  :doautocmd CursorMoved\<CR>

Search history may not be correctly updated

This is likely a bug of Vim itself. For some reason, search history is not correctly updated when searches are performed inside a Do block. The following test scenario fails due to this problem.

Execute (Clear search history):
  for _ in range(&history)
    call histdel('/', -1)

Given (Search and destroy):
  I'm a street walking cheetah with a heart full of napalm
  I'm a runaway son of the nuclear A-bomb
  I'm a world's forgotten boy
  The one who searches and destroys

Do (Searches):

Execute (Assertions):
  Log string(map(range(1, &history), 'histget("/", - v:val)'))
  AssertEqual 'runaway', histget('/', -2)
  AssertEqual 'search', histget('/', -1)

The result is given as follows:

Starting Vader: 1 suite(s), 3 case(s)
  Starting Vader: /Users/jg/.vim/plugged/vader.vim/search-and-destroy.vader
    (1/3) [EXECUTE] Clear search history
    (2/3) [  GIVEN] Search and destroy
    (2/3) [     DO] Searches
    (3/3) [  GIVEN] Search and destroy
    (3/3) [EXECUTE] Assertions
      > ['search', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '', '']
    (3/3) [EXECUTE] (X) Assertion failure: 'runaway' != ''
  Success/Total: 2/3
Success/Total: 2/3 (assertions: 0/1)
Elapsed time: 0.36 sec.