tests: Add tests for the :wv command.

test/functional/ex_cmds/wviminfo_spec.lua

@@ -0,0 +1,62 @@
+local helpers, lfs = require('test.functional.helpers'), require('lfs')
+local clear, execute, eq, neq, spawn, nvim_prog, set_session, wait =
+  helpers.clear, helpers.execute, helpers.eq, helpers.neq, helpers.spawn,
+  helpers.nvim_prog, helpers.set_session, helpers.wait
+
+-- Lua does not have a sleep function so we use the system command.  If the
+-- command does not support sub second precision we use math.floor() to get
+-- full seconds.
+local sleep = function(millisec)
+  local sec = millisec / 1000
+  local round = math.floor(sec)
+  if round == 0 then round = 1 end
+  os.execute('sleep '..sec..' || sleep '..round)
+end
+
+describe(':wviminfo', function()
+  local file = 'foo'
+  before_each(function()
+    clear()
+    os.remove(file)
+  end)
+
+  it('creates a file', function()
+    -- TODO
+    -- Set up the nvim session to be able to write viminfo files.  Is it
+    -- possible to do this outside of the it() call?
+    local nvim2 = spawn({nvim_prog, '-u', 'NONE', '--embed'})
+    --local nvim2 = spawn({nvim_prog, '-u', 'NONE', '--embed', '--cmd', 'let hans=42' })
+    set_session(nvim2)
+    --eq(43, eval('hans'))
+
+    -- Assert that the file does not exist.
+    eq(nil, lfs.attributes(file))
+    execute('wv! '..file)
+    wait()
+    -- Assert that the file does exist.
+    neq(nil, lfs.attributes(file))
+  end)
+
+  it('overwrites existing files', function()
+    -- TODO see above
+    local nvim2 = spawn({nvim_prog, '-u', 'NONE', '--embed'})
+    set_session(nvim2)
+
+    local text = 'foo test'
+
+    local fp = io.open(file, 'w')
+    fp:write(text)
+    fp:flush()
+    fp:close()
+    -- Assert that the file already exists.
+    neq(nil, lfs.attributes(file))
+    execute('wv! '..file)
+    wait()
+    -- Assert that the contents of the file changed.
+    neq(text, io.open(file):read())
+  end)
+
+  teardown(function()
+    os.remove(file)
+  end)
+end)