diff --git a/test/expand.vim b/test/expand.vim
new file mode 100644
index 0000000..a6bf9d2
--- /dev/null
+++ b/test/expand.vim
@@ -0,0 +1,120 @@
+let s:suite = themis#suite('expand')
+let s:assert = themis#helper('assert')
+
+function! s:suite.expand()
+  let g:lightline = {}
+  call lightline#init()
+  call s:assert.equals(SID('expand')([]),
+        \ [[], [], [0]])
+endfunction
+
+function! s:suite.default()
+  let g:lightline = {}
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['mode', 'paste'], ['readonly', 'filename', 'modified']]),
+        \ [[['mode', 'paste'], ['readonly', 'filename', 'modified']], [[0, 0], [0, 0, 0]], [0, 1, 2]])
+endfunction
+
+function! s:suite.custom()
+  function! Custom()
+    return [ 'left', 'middle', 'right' ]
+  endfunction
+  let g:lightline = { 'component_expand': { 'custom': 'Custom' } }
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['readonly', 'filename'], ['custom'], ['modified']]),
+        \ [[['readonly', 'filename'], ['left', 'middle', 'right'], ['modified']], [[0, 0], [1, 1, 1], [0]], [0, 1, 2, 3]])
+  call s:assert.equals(SID('expand')([['readonly', 'filename', 'custom', 'modified']]),
+        \ [[['readonly', 'filename', 'left', 'middle', 'right', 'modified']], [[0, 0, 1, 1, 1, 0]], [0, 1]])
+  delfunction Custom
+endfunction
+
+function! s:suite.custom_type()
+  function! Custom()
+    return [ 'left', 'middle', 'right' ]
+  endfunction
+  let g:lightline = { 'component_expand': { 'custom': 'Custom' }, 'component_type': { 'custom': 'custom' } }
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['readonly', 'filename'], ['custom'], ['modified']]),
+        \ [[['readonly', 'filename'], ['left'], ['middle'], ['right'], ['modified']], [[0, 0], [1], [1], [1], [0]], [0, 1, 'custom', 1, 2, 3]])
+  call s:assert.equals(SID('expand')([['readonly', 'filename', 'custom', 'modified']]),
+        \ [[['readonly', 'filename', 'left'], ['middle'], ['right', 'modified']], [[0, 0, 1], [1], [1, 0]], [0, 'custom', 0, 1]])
+  delfunction Custom
+endfunction
+
+function! s:suite.custom_string()
+  function! Custom()
+    return 'custom'
+  endfunction
+  let g:lightline = { 'component_expand': { 'custom': 'Custom' } }
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['readonly', 'filename'], ['custom'], ['modified']]),
+        \ [[['readonly', 'filename'], ['custom'], ['modified']], [[0, 0], [1], [0]], [0, 1, 2, 3]])
+  call s:assert.equals(SID('expand')([['readonly', 'filename', 'custom', 'modified']]),
+        \ [[['readonly', 'filename', 'custom', 'modified']], [[0, 0, 1, 0]], [0, 1]])
+  delfunction Custom
+endfunction
+
+function! s:suite.custom_type_string()
+  function! Custom()
+    return 'custom'
+  endfunction
+  let g:lightline = { 'component_expand': { 'custom': 'Custom' }, 'component_type': { 'custom': 'custom' } }
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['readonly', 'filename'], ['custom'], ['modified']]),
+        \ [[['readonly', 'filename'], ['custom'], ['modified']], [[0, 0], [1], [0]], [0, 'custom', 2, 3]])
+  call s:assert.equals(SID('expand')([['readonly', 'filename', 'custom', 'modified']]),
+        \ [[['readonly', 'filename'], ['custom'], ['modified']], [[0, 0], [1], [0]], [0, 'custom', 0, 1]])
+  delfunction Custom
+endfunction
+
+function! s:suite.custom_number()
+  function! Custom()
+    return 24
+  endfunction
+  let g:lightline = { 'component_expand': { 'custom': 'Custom' } }
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['readonly', 'filename'], ['custom'], ['modified']]),
+        \ [[['readonly', 'filename'], ['24'], ['modified']], [[0, 0], [1], [0]], [0, 1, 2, 3]])
+  call s:assert.equals(SID('expand')([['readonly', 'filename', 'custom', 'modified']]),
+        \ [[['readonly', 'filename', '24', 'modified']], [[0, 0, 1, 0]], [0, 1]])
+  delfunction Custom
+endfunction
+
+function! s:suite.custom_type_number()
+  function! Custom()
+    return 24
+  endfunction
+  let g:lightline = { 'component_expand': { 'custom': 'Custom' }, 'component_type': { 'custom': 'custom' } }
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['readonly', 'filename'], ['custom'], ['modified']]),
+        \ [[['readonly', 'filename'], ['24'], ['modified']], [[0, 0], [1], [0]], [0, 'custom', 2, 3]])
+  call s:assert.equals(SID('expand')([['readonly', 'filename', 'custom', 'modified']]),
+        \ [[['readonly', 'filename'], ['24'], ['modified']], [[0, 0], [1], [0]], [0, 'custom', 0, 1]])
+  delfunction Custom
+endfunction
+
+function! s:suite.custom_mixed()
+  function! Custom()
+    return ['left', { 'custom': 24 }, [function('tr')]]
+  endfunction
+  let g:lightline = { 'component_expand': { 'custom': 'Custom' } }
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['readonly', 'filename'], ['custom'], ['modified']]),
+        \ [[['readonly', 'filename'], ['left', '{''custom'': 24}', 'function(''tr'')'], ['modified']], [[0, 0], [1, 1, 1], [0]], [0, 1, 2, 3]])
+  call s:assert.equals(SID('expand')([['readonly', 'filename', 'custom', 'modified']]),
+        \ [[['readonly', 'filename', 'left', '{''custom'': 24}', 'function(''tr'')', 'modified']], [[0, 0, 1, 1, 1, 0]], [0, 1]])
+  delfunction Custom
+endfunction
+
+function! s:suite.custom_type_mixed()
+  function! Custom()
+    return ['left', { 'custom': 24 }, [function('tr')]]
+  endfunction
+  let g:lightline = { 'component_expand': { 'custom': 'Custom' }, 'component_type': { 'custom': 'custom' } }
+  call lightline#init()
+  call s:assert.equals(SID('expand')([['readonly', 'filename'], ['custom'], ['modified']]),
+        \ [[['readonly', 'filename'], ['left'], ['{''custom'': 24}'], ['function(''tr'')'], ['modified']], [[0, 0], [1], [1], [1], [0]], [0, 1, 'custom', 1, 2, 3]])
+  call s:assert.equals(SID('expand')([['readonly', 'filename', 'custom', 'modified']]),
+        \ [[['readonly', 'filename', 'left'], ['{''custom'': 24}'], ['function(''tr'')', 'modified']], [[0, 0, 1], [1], [1, 0]], [0, 'custom', 0, 1]])
+  delfunction Custom
+endfunction