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

• Unit testing is achieved by compiling the tests as a shared library which is loaded and called by LuaJit FFI.
• Functional tests are driven by RPC, so they do not require LuaJit (as opposed to Lua).

You can learn the key concepts of Lua in 15 minutes. Use any existing test as a template to start writing new tests.

Tests are run by /cmake/RunTests.cmake file, using busted (a Lua test-runner). For some failures, .nvimlog (or $NVIM_LOG_FILE) may provide insight.

Depending on the presence of binaries (e.g., xclip) some tests will be ignored. You must compile with libintl to prevent E319: The command is not available in this version errors.

• Running tests
• Writing tests
• Lint
• Configuration

• /test/benchmark : benchmarks
• /test/functional : functional tests
• /test/unit : unit tests
• /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 preloaded by busted --helper option
• /test/**/helpers.lua : common utility functions for test code
• /test/*/**/*_spec.lua : actual tests. Files that do not end with _spec.lua are libraries like /test/**/helpers.lua, except that they have some common topic.
• /src/nvim/testdir : old tests (from Vim)

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 all legacy Vim tests:

make oldtest

To run a single legacy test file you can use either:

make oldtest TEST_FILE=test_syntax.vim

or:

make src/nvim/testdir/test_syntax.vim

• Specify only the test file name, not the full path.

• 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_process_exit:400: exited: pid=58017 status=0 stoptime=0
  

• You can set $GDB to run tests under gdbserver. And if $VALGRIND is set it will pass --vgdb=yes to valgrind instead of starting gdbserver directly.
• Hanging tests can happen due to unexpected "press-enter" prompts. The default screen width is 50 columns. Commands that try to print lines longer than 50 columns in the command-line, e.g. :edit very...long...path, will trigger the 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.

Another filter method is 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

To run a specific unit test:

TEST_FILE=test/unit/foo.lua make unittest

To run a specific functional test:

TEST_FILE=test/functional/foo.lua make functionaltest

To repeat a test:

BUSTED_ARGS="--repeat=100 --no-keep-going" TEST_FILE=test/functional/foo_spec.lua make functionaltest

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().

• Luajit needs to know about type and constant declarations used in function prototypes. The helpers.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() to skip tests (example). 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. Provide empty function argument if the pending() call is outside it() (example).
• Really long source([=[...]=]) blocks may break Vim's Lua syntax highlighting. Try :syntax sync fromstart to fix it.

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 and 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.

make lint (and make lualint) runs luacheck on the test code.

If a luacheck warning must be ignored, specify the warning code. Example:

-- luacheck: ignore 621

https://luacheck.readthedocs.io/en/stable/warnings.html

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

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):

• BUSTED_ARGS (F) (U): arguments forwarded to busted.

• 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/helpers.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.

• 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_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_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 there 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.