*dev_test.txt*          Nvim


                            NVIM REFERENCE MANUAL


Writing tests for Nvim                                              *dev-test*

                                  Type |gO| to see the table of contents.

==============================================================================
Writing tests for Nvim

Nvim has a powerful yet simple test framework. It's approximately 7x better
than whatever you use at work.

Each test starts a new Nvim process (10-30ms) which is discarded after the
test finishes. You assert stuff using `t.eq()` and `screen:expect()` (which
automatically waits as needed). That's pretty much it.

TODO: Expose the test framework as a public interface, for use in 3P plugins:
https://github.com/neovim/neovim/issues/34592

==============================================================================
Test framework

Tests are broadly divided into unit tests (`test/unit/`), functional tests
(`test/functional/`) and old tests (`test/old/testdir/`).

- Unit testing is achieved by compiling the tests as a shared library which is
  loaded and called by [LuaJit FFI](https://luajit.org/ext_ffi.html).
- Functional tests are driven by RPC, so they do not require LuaJit (as
  opposed to Lua). They are essentially "integration" tests, they test the
  full system. But they are fast.

You can learn [Lua concepts 15 minutes](https://learnxinyminutes.com/docs/lua/),
see also |lua-guide|. Use any existing test as a template to start writing new
tests, or see |dev-quickstart|.

Tests are run by the `/cmake/RunTests.cmake` script using the repo-local Lua
test harness in `/test/harness.lua`.
For some failures, `./build/nvim.log` (or `$NVIM_LOG_FILE`) may provide insight.

Depending on the presence of binaries (e.g., `xclip`) some tests will be
skipped.

Harness isolation                                  *dev-test-harness-isolation*

The Lua harness runs all selected spec files in one low-level `nvim -ll`
process, then restores a baseline before each file. For each suite iteration,
the file boundary baseline is captured after `--helper` is loaded, so
helper-provided modules and defaults persist across files.
Helper files are preload-only: they may require modules, set defaults, and
register suite-end cleanup, but they do not define tests or hooks.

The harness restores `_G`, `package.loaded`, `package.preload`, `arg`, and the
process environment with the same shallow file boundary model that busted uses.

==============================================================================
Test Layout

- `/test/benchmark` : benchmarks
- `/test/functional` : functional tests
- `/test/unit` : unit tests
- `/test/old/testdir` : old tests (from Vim)
- `/test/config` : contains `*.in` files which are transformed into `*.lua`
  files using `configure_file` CMake command: this is for accessing CMake
  variables in Lua tests.
- `/test/includes` : include-files for use by luajit `ffi.cdef` C definitions
  parser: normally used to make macros not accessible via this mechanism
  accessible the other way.
- `/test/*/preload.lua` : modules and defaults preloaded by the harness
  `--helper` option
- `/test/**/testutil.lua` : common utility functions in the context of the test
  runner
- `/test/**/testnvim.lua` : common utility functions in the context of the
  test session (RPC channel to the Nvim child process created by clear() for each test)
- `/test/*/**/*_spec.lua` : actual tests. Files that do not end with
  `_spec.lua` are libraries like `/test/**/testutil.lua`, except that they have
  some common topic.


==============================================================================
Running tests                                                   *dev-run-test*

EXECUTING TESTS

To run all tests (except "old" tests): >
    make test

To run only _unit_ tests: >
    make unittest

To run only _functional_ tests: >
    make functionaltest

To run functional tests in parallel (used in CI): >
    cmake --build build --target functionaltest-parallel -j2
    cmake --build build --target functionaltest-summary


LEGACY TESTS

To run all legacy Vim tests: >
    make oldtest

To run a _single_ legacy test file you can use either: >
    # Specify only the test file name, not the full path.
    make oldtest TEST_FILE=test_syntax.vim
or: >
    make test/old/testdir/test_syntax.vim


DEBUGGING TESTS

- Each test gets a test id which looks like "T123". This also appears in the
  log file. Child processes spawned from a test appear in the logs with the
  _parent_ name followed by "/c". Example: >

    DBG 2022-06-15T18:37:45.226 T57.58016.0   UI: flush
    DBG 2022-06-15T18:37:45.226 T57.58016.0   inbuf_poll:442: blocking... events_enabled=0 events_pending=0
    DBG 2022-06-15T18:37:45.227 T57.58016.0/c UI: stop
    INF 2022-06-15T18:37:45.227 T57.58016.0/c os_exit:595: Nvim exit: 0
    DBG 2022-06-15T18:37:45.229 T57.58016.0   read_cb:118: closing Stream (0x7fd5d700ea18): EOF (end of file)
    INF 2022-06-15T18:37:45.229 T57.58016.0   on_proc_exit:400: exited: pid=58017 status=0 stoptime=0

- You can set `$GDB` to [run functional tests under gdbserver](https://github.com/neovim/neovim/pull/1527): >sh
    GDB=1 TEST_FILE=test/functional/api/buffer_spec.lua TEST_FILTER='nvim_buf_set_text works$' make functionaltest
<
  Read more about |dev-filter-test|.

  Then, in another terminal: >sh
    gdb -ex 'target remote localhost:7777' build/bin/nvim
<
  If `$VALGRIND` is also set it will pass `--vgdb=yes` to valgrind instead of
  starting gdbserver directly.

  See `nvim_argv` in `test/functional/testnvim.lua`.

- Hanging tests can happen due to unexpected modal prompts (waiting for user
  input). The default screen width is 50 columns.
  - Commands that try to print lines longer than 50 columns in the cmdline,
    e.g. `:edit very...long...path`, will trigger the hit-enter prompt. Try
    using a shorter path, or `:silent edit`.
- If you can't figure out what is going on, try to visualize the screen. Put
  this at the beginning of your test: >
    local Screen = require('test.functional.ui.screen')
    local screen = Screen.new()
    screen:attach()
<  Then put `screen:snapshot_util()` anywhere in your test. See the comments in
  `test/functional/ui/screen.lua` for more info.

DEBUGGING LUA TEST CODE

Debugging Lua test code is a bit involved. Get your shopping list ready, you'll
need to install and configure:

1. [nvim-dap](https://github.com/mfussenegger/nvim-dap)
2. [local-lua-debugger-vscode](https://github.com/mfussenegger/nvim-dap/wiki/Debug-Adapter-installation#local-lua-debugger-vscode)
3. [nlua](https://github.com/mfussenegger/nlua)
4. [one-small-step-for-vimkind](https://github.com/jbyuki/one-small-step-for-vimkind) (called `osv`)
5. An `nlua` command in `$PATH`.


The setup roughly looks like this: >

    ┌─────────────────────────┐
    │ nvim used for debugging │◄────┐
    └─────────────────────────┘     │
               │                    │
               ▼                    │
      ┌─────────────────┐           │
      │ local-lua-debug │           │
      └─────────────────┘           │
              │                     │
              ▼                     │
         ┌─────────┐                │
         │   nlua  │                │
         └─────────┘                │
              │                     │
              ▼                     │
         ┌───────────┐              │
         │ test-case │              │
         └───────────┘              │
              │                     │
              ▼                     │
      ┌────────────────────┐        │
      │ nvim test-instance │        │
      └────────────────────┘        │
        │   ┌─────┐                 │
        └──►│ osv │─────────────────┘
            └─────┘


With these installed you can use a configuration like this: >

    local dap = require("dap")


    local function free_port()
      local tcp = vim.loop.new_tcp()
      assert(tcp)
      tcp:bind('127.0.0.1', 0)
      local port = tcp:getsockname().port
      tcp:shutdown()
      tcp:close()
      return port
    end


    local name = "nvim-test-case" -- arbitrary name
    local config = {
      name = name,

      -- value of type must match the key used in `dap.adapters["local-lua"] = ...` from step 2)
      type = "local-lua",

      request = "launch",
      cwd = "${workspaceFolder}",
      program = {
        command = "nlua",
      },
      args = {
        "-ll",
        "test/runner.lua",
        "--helper=test/functional/preload.lua",
        "--lpath=build/?.lua",
        "--lpath=?.lua",

        -- path to file to debug, could be replaced with a hardcoded string
        function()
          return vim.api.nvim_buf_get_name(0)
        end,

        -- You can filter to specific test-case by adding:
        -- '--filter="' .. test_case_name .. '"',
      },
      env = {
        OSV_PORT = free_port
      }
    }

    -- Whenever the config is used it needs to launch a second debug session that attaches to `osv`
    -- This makes it possible to step into `exec_lua` code blocks
    setmetatable(config, {

      __call = function(c)
        ---@param session dap.Session
        dap.listeners.after.event_initialized["nvim_debug"] = function(session)
          if session.config.name ~= name then
            return
          end
          dap.listeners.after.event_initialized["nvim_debug"] = nil
          vim.defer_fn(function()
            dap.run({
              name = "attach-osv",
              type = "nlua", -- value must match the `dap.adapters` definition key for osv
              request = "attach",
              port = session.config.env.OSV_PORT,
            })
          end, 500)
        end

        return c
      end,
    })


You can either add this configuration to your `dap.configurations.lua` list as
described in `:help dap-configuration` or create it dynamically in a
user-command or function and call it directly via `dap.run(config)`. The latter
is useful if you use treesitter to find the test case around a cursor location
with a query like the following and set the `--filter` property to it. >query

    (function_call
      name: (identifier) @name (#any-of? @name "describe" "it")
      arguments: (arguments
        (string) @str
      )
    )

Limitations:

- You need to add the following boilerplate to each spec file where you want to
  be able to stop at breakpoints within the test-case code: >
    if os.getenv("LOCAL_LUA_DEBUGGER_VSCODE") == "1" then
      require("lldebugger").start()
    end
<  This is a local-lua-debugger limitation.
- You cannot step into code of files which get baked into the nvim binary
  (such as `_core/*.lua` and `inspect.lua`).


------------------------------------------------------------------------------
Filtering tests                                              *dev-filter-test*

FILTER BY NAME

Tests can be filtered by setting a pattern of test name to `TEST_FILTER` or `TEST_FILTER_OUT`. >

    it('foo api',function()
      ...
    end)
    it('bar api',function()
      ...
    end)

To run only test with filter name: >
    TEST_FILTER='foo.*api' make functionaltest

To run all tests except ones matching a filter: >
    TEST_FILTER_OUT='foo.*api' make functionaltest

FILTER BY FILE

To run a _specific_ unit test: >
    TEST_FILE=test/unit/foo.lua make unittest

or >
    cmake -E env "TEST_FILE=test/unit/foo.lua" cmake --build build --target unittest

To run a _specific_ functional test: >
    TEST_FILE=test/functional/foo.lua make functionaltest

or >
    cmake -E env "TEST_FILE=test/functional/foo.lua" cmake --build build --target functionaltest

To _repeat_ a test: >
    TEST_ARGS="--repeat=100 --no-keep-going" TEST_FILE=test/functional/foo_spec.lua make functionaltest

or >
    cmake -E env "TEST_FILE=test/functional/foo_spec.lua" cmake -E env TEST_ARGS="--repeat=100 --no-keep-going" cmake --build build --target functionaltest

FILTER BY TAG

Tests can be "tagged" by adding `#` before a token in the test description. >

    it('#foo bar baz', function()
      ...
    end)
    it('#foo another test', function()
      ...
    end)

To run only the tagged tests: >
    TEST_TAG=foo make functionaltest

NOTE:

- `TEST_FILE` is not a pattern string like `TEST_TAG` or `TEST_FILTER`. The
  given value to `TEST_FILE` must be a path to an existing file.
- Both `TEST_TAG` and `TEST_FILTER` filter tests by the string descriptions
  found in `it()` and `describe()`.


==============================================================================
Writing tests                                                 *dev-write-test*

GUIDELINES

- CI runs tests in parallel via the `functionaltest-parallel` cmake target.
- The Nvim test instance CWD is isolated to per "test group" (see
  `WORKING_DIRECTORY` in `cmake/RunTests.cmake`), so tests can write files to
  CWD without interfering with other tests running in parallel.
- Luajit needs to know about type and constant declarations used in function
  prototypes. The
  [testutil.lua](https://github.com/neovim/neovim/blob/master/test/unit/testutil.lua)
  file automatically parses `types.h`, so types used in the tested functions
  could be moved to it to avoid having to rewrite the declarations in the test
  files.
  - `#define` constants must be rewritten `const` or `enum` so they can be
    "visible" to the tests.
- Use `pending()` or `t.skip()` to skip tests.
  - Example: https://github.com/neovim/neovim/commit/5c1dc0fbe7388528875aff9d7b5055ad718014de#diff-bf80b24c724b0004e8418102f68b0679R18
  - Note: If a test is skipped because of a non-actionable reason, we don't
    want it to appear in the "pending" list. Include "N/A" in the skip
    description, then it won't be added to the "pending" list. For example, if
    a test is skipped because it's running on a non-LuaJit system, including
    it in the "pending" list is just noise. Thus, its pending reason should
    say "N/A": >
    pending('N/A: missing LuaJIT FFI')
<
  - Do not silently skip the test with `if-else`. If a functional test depends
    on some external factor (e.g. the existence of `md5sum` on `$PATH`), _and_
    you can't mock or fake the dependency, then skip the test via `pending()`
    if the external factor is missing. This ensures that the _total_
    test-count (success + fail + error + pending) is the same in all
    environments.
    - Note: `pending()` is ignored if it is missing an argument, unless it is
      [contained in an `it()` block](https://github.com/neovim/neovim/blob/d21690a66e7eb5ebef18046c7a79ef898966d786/test/functional/ex_cmds/grep_spec.lua#L11).
      Provide empty function argument if the `pending()` call is outside `it()`
      Example: https://github.com/neovim/neovim/commit/5c1dc0fbe7388528875aff9d7b5055ad718014de#diff-bf80b24c724b0004e8418102f68b0679R18

WHERE TESTS GO

Tests in `/test/unit` and `/test/functional` are divided into groups by the
semantic component they are testing.

- Unit tests (`test/unit/`) should match 1-to-1 with the structure of
  `src/nvim/`, because they are testing functions directly. E.g. unit-tests
  for `src/nvim/undo.c` should live in `test/unit/undo_spec.lua`.
- Functional tests (`test/functional/`) are higher-level (plugins, UI, user
  input) than unit tests; they are organized by concept.
    - Try to find an existing `test/functional/*/*_spec.lua` group that makes
      sense, before creating a new one.


------------------------------------------------------------------------------
Fixing tests                                                    *dev-fix-test*

FIXING HARNESS WARNINGS

> Nvim session T123 took 2000 milliseconds to exit
> This indicates a likely problem with the test even if it passed!

This may indicate a leak, because Nvim waits on uv handles before exiting.
Example: https://github.com/neovim/neovim/pull/35768


FIXING LINT FAILURES

`make lint` (and `make lintlua`) runs [LuaLS](https://github.com/LuaLS/lua-language-server/wiki/Annotations)
on the test code.

If a LuaLS/EmmyLS warning must be ignored, specify the warning code. Example: >lua

    ---@diagnostic disable-next-line: unused-vararg

https://github.com/LuaLS/lua-language-server/wiki/Annotations#diagnostic

Ignore the smallest applicable scope (e.g. inside a function, not at the top of
the file).


==============================================================================
Configuration                                                *dev-test-config*

(TODO: clean this up, too many variables and some of them are not used anymore.)

Test behaviour is affected by environment variables. Currently supported
(Functional, Unit, Benchmarks) (when Defined; when set to _1_; when defined,
treated as Integer; when defined, treated as String; when defined, treated as
Number; !must be defined to function properly):

- `TEST_ARGS` (F) (U): arguments forwarded to the local test harness.

- `CC` (U) (S): specifies which C compiler to use to preprocess files.
  Currently only compilers with gcc-compatible arguments are supported.

- `GDB` (F) (D): makes nvim instances to be run under `gdbserver`. It will be
  accessible on `localhost:7777`: use `gdb build/bin/nvim`, type `target remote :7777` inside.

- `GDBSERVER_PORT` (F) (I): overrides port used for `GDB`.

- `LOG_DIR` (FU) (S!): specifies where to seek for valgrind and ASAN log files.

- `VALGRIND` (F) (D): makes nvim instances to be run under `valgrind`. Log
  files are named `valgrind-%p.log` in this case. Note that non-empty valgrind
  log may fail tests. Valgrind arguments may be seen in
  `/test/functional/testnvim.lua`. May be used in conjunction with `GDB`.

- `VALGRIND_LOG` (F) (S): overrides valgrind log file name used for `VALGRIND`.

- `TEST_COLORS` (F) (U) (D): enable pretty colors in test runner. Set to true by default.

- `TEST_SKIP_FRAGILE` (F) (D): makes test suite skip some fragile tests.

- `TEST_TIMEOUT` (FU) (I): specifies maximum time, in seconds, before the test
  suite run is killed

- `NVIM_TEST` (FU) (D): lets Nvim process detect that it is running in a test.

- `NVIM_LUA_NOTRACK` (F) (D): disable reference counting of Lua objects

- `NVIM_PRG` (F) (S): path to Nvim executable (default: `build/bin/nvim`).

- `NVIM_TEST_MAIN_CDEFS` (U) (1): makes `ffi.cdef` run in main process. This
  raises a possibility of bugs due to conflicts in header definitions, despite
  the counters, but greatly speeds up unit tests by not requiring `ffi.cdef` to
  do parsing of big strings with C definitions.

- `NVIM_TEST_PRINT_I` (U) (1): makes `cimport` print preprocessed, but not yet
  filtered through `formatc` headers. Used to debug `formatc`. Printing is done
  with the line numbers.

- `NVIM_TEST_PRINT_CDEF` (U) (1): makes `cimport` print final lines which will
  be then passed to `ffi.cdef`. Used to debug errors `ffi.cdef` happens to
  throw sometimes.

- `NVIM_TEST_PRINT_SYSCALLS` (U) (1): makes it print to stderr when syscall
  wrappers are called and what they returned. Used to debug code which makes
  unit tests be executed in separate processes.

- `NVIM_TEST_RUN_FAILING_TESTS` (U) (1): makes `itp` run tests which are known
  to fail (marked by setting third argument to `true`).

- `NVIM_TEST_CORE_*` (FU) (S): a set of environment variables which specify
  where to search for core files. Are supposed to be defined all at once.

- `NVIM_TEST_CORE_GLOB_DIRECTORY` (FU) (S): directory where core files are
  located. May be `.`. This directory is then recursively searched for core
  files. Note: this variable must be defined for any of the following to have
  any effect.

- `NVIM_TEST_CORE_GLOB_RE` (FU) (S): regular expression which must be matched
  by core files. E.g. `/core[^/]*$`. May be absent, in which case any file is
  considered to be matched.

- `NVIM_TEST_CORE_EXC_RE` (FU) (S): regular expression which excludes certain
  directories from searching for core files inside. E.g. use `^/%.deps$` to not
  search inside `/.deps`. If absent, nothing is excluded.

- `NVIM_TEST_CORE_DB_CMD` (FU) (S): command to get backtrace out of the
  debugger. E.g. `gdb -n -batch -ex "thread apply all bt full"
  "$_NVIM_TEST_APP" -c "$_NVIM_TEST_CORE"`. Defaults to the example command.
  This debug command may use environment variables `_NVIM_TEST_APP` (path to
  application which is being debugged: normally either nvim or luajit) and
  `_NVIM_TEST_CORE` (core file to get backtrace from).

- `NVIM_TEST_CORE_RANDOM_SKIP` (FU) (D): makes `check_cores` not check cores
  after approximately 90% of the tests. Should be used when finding cores is
  too hard for some reason. Normally (on OS X or when
  `NVIM_TEST_CORE_GLOB_DIRECTORY` is defined and this variable is not) cores
  are checked for after each test.

- `NVIM_TEST_INTEG` (F) (D): enables integration tests that makes real network
  calls. By default these tests are skipped. When set to `1`, tests requiring external
  HTTP requests (e.g `vim.net.request()`) will be run.

- `NVIM_TEST_RUN_TESTTEST` (U) (1): allows running
  `test/unit/testtest_spec.lua` used to check how testing infrastructure works.

- `NVIM_TEST_TRACE_LEVEL` (U) (N): specifies unit tests tracing level:
  - `0` disables tracing (the fastest, but you get no data if tests crash and
    no core dump was generated),
  - `1` leaves only C function calls and returns in the trace (faster than
    recording everything),
  - `2` records all function calls, returns and executed Lua source lines.

- `NVIM_TEST_TRACE_ON_ERROR` (U) (1): makes unit tests yield trace on error in
  addition to regular error message.

- `NVIM_TEST_MAXTRACE` (U) (N): specifies maximum number of trace lines to
  keep. Default is 1024.

- `OSV_PORT`: (F): launches `osv` listening on the given port within nvim test
  instances.


 vim:tw=78:ts=8:sw=4:et:ft=help:norl:
