test: Use lua to perform sanity API checks

Sanity API checks made by the python-client in the api-python travis target were
converted to lua and will now live in this repository. This will simplify
performing breaking changes to the API as it won't be necessary to send parallel
PRs the python-client.

test/functional/api/buffer_spec.lua

@@ -0,0 +1,118 @@
+-- Sanity checks for buffer_* API calls via msgpack-rpc
+local helpers = require('test.functional.helpers')
+local clear, nvim, buffer, curbuf, curwin, eq, ok =
+  helpers.clear, helpers.nvim, helpers.buffer, helpers.curbuf, helpers.curwin,
+  helpers.eq, helpers.ok
+
+describe('buffer_* functions', function()
+  before_each(clear)
+
+  describe('line_count, insert and del_line', function()
+    it('works', function()
+      eq(1, curbuf('line_count'))
+      curbuf('insert', -1, {'line'})
+      eq(2, curbuf('line_count'))
+      curbuf('insert', -1, {'line'})
+      eq(3, curbuf('line_count'))
+      curbuf('del_line', -1)
+      eq(2, curbuf('line_count'))
+      curbuf('del_line', -1)
+      curbuf('del_line', -1)
+      -- There's always at least one line
+      eq(1, curbuf('line_count'))
+    end)
+  end)
+
+
+  describe('{get,set,del}_line', function()
+    it('works', function()
+      eq('', curbuf('get_line', 0))
+      curbuf('set_line', 0, 'line1')
+      eq('line1', curbuf('get_line', 0))
+      curbuf('set_line', 0, 'line2')
+      eq('line2', curbuf('get_line', 0))
+      curbuf('del_line', 0)
+      eq('', curbuf('get_line', 0))
+    end)
+  end)
+
+
+  describe('{get,set}_line_slice', function()
+    it('works', function()
+      eq({''}, curbuf('get_line_slice', 0, -1, true, true))
+      -- Replace buffer
+      curbuf('set_line_slice', 0, -1, true, true, {'a', 'b', 'c'})
+      eq({'a', 'b', 'c'}, curbuf('get_line_slice', 0, -1, true, true))
+      eq({'b', 'c'}, curbuf('get_line_slice', 1, -1, true, true))
+      eq({'b'}, curbuf('get_line_slice', 1, 2, true, false))
+      eq({}, curbuf('get_line_slice', 1, 1, true, false))
+      eq({'a', 'b'}, curbuf('get_line_slice', 0, -1, true, false))
+      eq({'b'}, curbuf('get_line_slice', 1, -1, true, false))
+      eq({'b', 'c'}, curbuf('get_line_slice', -2, -1, true, true))
+      curbuf('set_line_slice', 1, 2, true, false, {'a', 'b', 'c'})
+      eq({'a', 'a', 'b', 'c', 'c'}, curbuf('get_line_slice', 0, -1, true, true))
+      curbuf('set_line_slice', -1, -1, true, true, {'a', 'b', 'c'})
+      eq({'a', 'a', 'b', 'c', 'a', 'b', 'c'},
+        curbuf('get_line_slice', 0, -1, true, true))
+      curbuf('set_line_slice', 0, -3, true, false, {})
+      eq({'a', 'b', 'c'}, curbuf('get_line_slice', 0, -1, true, true))
+      curbuf('set_line_slice', 0, -1, true, true, {})
+      eq({''}, curbuf('get_line_slice', 0, -1, true, true))
+    end)
+  end)
+
+  describe('{get,set}_var', function()
+    it('works', function()
+      curbuf('set_var', 'lua', {1, 2, {['3'] = 1}})
+      eq({1, 2, {['3'] = 1}}, curbuf('get_var', 'lua'))
+      eq({1, 2, {['3'] = 1}}, nvim('eval', 'b:lua'))
+    end)
+  end)
+
+  describe('{get,set}_option', function()
+    it('works', function()
+      eq(8, curbuf('get_option', 'shiftwidth'))
+      curbuf('set_option', 'shiftwidth', 4)
+      eq(4, curbuf('get_option', 'shiftwidth'))
+      -- global-local option
+      curbuf('set_option', 'define', 'test')
+      eq('test', curbuf('get_option', 'define'))
+      -- Doesn't change the global value
+      eq([[^\s*#\s*define]], nvim('get_option', 'define'))
+    end)
+  end)
+
+  describe('{get,set}_name', function()
+    it('works', function()
+      nvim('command', 'new')
+      eq('', curbuf('get_name'))
+      local new_name = nvim('eval', 'resolve(tempname())')
+      curbuf('set_name', new_name)
+      eq(new_name, curbuf('get_name'))
+      nvim('command', 'w!')
+      local f = io.open(new_name)
+      ok(f ~= nil)
+      f:close()
+      os.remove(new_name)
+    end)
+  end)
+
+  describe('is_valid', function()
+    it('works', function()
+      nvim('command', 'new')
+      local b = nvim('get_current_buffer')
+      ok(buffer('is_valid', b))
+      nvim('command', 'bw!')
+      ok(not buffer('is_valid', b))
+    end)
+  end)
+
+  describe('get_mark', function()
+    it('works', function()
+      curbuf('insert', -1, {'a', 'bit of', 'text'})
+      curwin('set_cursor', {3, 4})
+      nvim('command', 'mark V')
+      eq({3, 0}, curbuf('get_mark', 'V'))
+    end)
+  end)
+end)