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README.md

@@ -1,23 +1,70 @@
-# xVimscript
+# Exercism Vim script Track
 
-![build status](https://travis-ci.org/exercism/xvimscript.svg?branch=master)
+[![Join the chat at https://gitter.im/exercism/vimscript](https://badges.gitter.im/exercism/vimscript.svg)](https://gitter.im/exercism/vimscript?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
-Exercism exercises in Vim script.
-
-## Contributing
+![build status](https://travis-ci.org/exercism/vimscript.svg?branch=master)
+[![Join the chat at https://gitter.im/exercism/xvimscript](https://badges.gitter.im/exercism/xvimscript.svg)](https://gitter.im/exercism/xvimscript?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 We welcome any kind of contribution!
 
 If you have a suggestion or question, create a new
-[issue](https://github.com/exercism/xvimscript/issues).
+[issue](https://github.com/exercism/vimscript/issues).
 
 For code or fixing typos and similar things, open a
-[pull request](https://github.com/exercism/xvimscript/pulls).
+[pull request](https://github.com/exercism/vimscript/pulls).
 
-Look at recent [commits](https://github.com/exercism/xvimscript/commits/master)
+Look at recent [commits](https://github.com/exercism/vimscript/commits/master)
 to get a feeling on how to format your own ones.
 
 Even if there are any uncertainties, go for it nevertheless. We can straighten
 out everything in the process.
 
 Thank you for contributing! :tada:
+
+## Linting Vim files
+
+If you add or change a Vim file, the CI will use vint to ensure best practices.
+Therefore it's recommended idea to run it locally first, before creating a pull
+request.
+
+1. Install [vint](https://github.com/Kuniwak/vint#quick-start).
+1. Recursively lint all Vim files:
+    ```
+    $ vint .
+    ```
+
+## Writing test files
+
+#### Generating test files
+
+Use the [generator](lib/generate.vim) to create Vader files from their canonical
+test data:
+
+```vim
+" in Vim
+:source lib/generate.vim
+:Generate word-count
+```
+
+This would fetch the [canonical test data](https://raw.githubusercontent.com/exercism/x-common/master/exercises/word-count/canonical-data.json),
+decode the JSON to Vim data types, iterate over the result, and put the tests in
+a new unnamed buffer.
+
+_This script requires Vim 7.4.1304+ for `json_decode()`. It also relies on the
+netrw plugin (`:h netrw`), but that one is shipped and sourced by default._
+
+#### Type mismatch exceptions
+
+Older Vims don't like changing types for the same variable. If your tests use
+global variables, `unlet!` them in a `Before` block at the top of the Vader file.
+
+When each test uses `let expected = ...`, then put this at the top:
+
+```vim
+Before:
+  unlet! expected
+```
+
+This is patched as of
+[Vim 7.4.1546](https://github.com/vim/vim/commit/f6f32c38bf3319144a84a01a154c8c91939e7acf),
+but we shouldn't assume versions in favor of compatibility.