diff --git a/test/concatenate.vim b/test/concatenate.vim
new file mode 100644
index 0000000..f719940
--- /dev/null
+++ b/test/concatenate.vim
@@ -0,0 +1,82 @@
+let s:suite = themis#suite('concatenate')
+let s:assert = themis#helper('assert')
+
+function! s:suite.before_each()
+  let g:lightline = { 'subseparator': { 'left': '>', 'right': '<' } }
+  call lightline#init()
+endfunction
+
+function! s:suite.nil()
+  call s:assert.equals(lightline#concatenate([], 0), '')
+  call s:assert.equals(lightline#concatenate([], 1), '')
+endfunction
+
+function! s:suite.one()
+  call s:assert.equals(lightline#concatenate(['foo'], 0), 'foo')
+  call s:assert.equals(lightline#concatenate(['foo'], 1), 'foo')
+endfunction
+
+function! s:suite.two()
+  call s:assert.equals(lightline#concatenate(['foo', 'bar'], 0), 'foo > bar')
+  call s:assert.equals(lightline#concatenate(['foo', 'bar'], 1), 'foo < bar')
+endfunction
+
+function! s:suite.three()
+  call s:assert.equals(lightline#concatenate(['foo', 'bar', 'baz'], 0), 'foo > bar > baz')
+  call s:assert.equals(lightline#concatenate(['foo', 'bar', 'baz'], 1), 'foo < bar < baz')
+endfunction
+
+function! s:suite.one_empty()
+  call s:assert.equals(lightline#concatenate([''], 0), '')
+  call s:assert.equals(lightline#concatenate([''], 1), '')
+endfunction
+
+function! s:suite.two_empty_left()
+  call s:assert.equals(lightline#concatenate(['', 'bar'], 0), 'bar')
+  call s:assert.equals(lightline#concatenate(['', 'bar'], 1), 'bar')
+endfunction
+
+function! s:suite.two_empty_right()
+  call s:assert.equals(lightline#concatenate(['foo', ''], 0), 'foo')
+  call s:assert.equals(lightline#concatenate(['foo', ''], 1), 'foo')
+endfunction
+
+function! s:suite.two_empty_both()
+  call s:assert.equals(lightline#concatenate(['', ''], 0), '')
+  call s:assert.equals(lightline#concatenate(['', ''], 1), '')
+endfunction
+
+function! s:suite.three_empty_left()
+  call s:assert.equals(lightline#concatenate(['', 'bar', 'baz'], 0), 'bar > baz')
+  call s:assert.equals(lightline#concatenate(['', 'bar', 'baz'], 1), 'bar < baz')
+endfunction
+
+function! s:suite.three_empty_middle()
+  call s:assert.equals(lightline#concatenate(['foo', '', 'baz'], 0), 'foo > baz')
+  call s:assert.equals(lightline#concatenate(['foo', '', 'baz'], 1), 'foo < baz')
+endfunction
+
+function! s:suite.three_empty_right()
+  call s:assert.equals(lightline#concatenate(['foo', 'bar', ''], 0), 'foo > bar')
+  call s:assert.equals(lightline#concatenate(['foo', 'bar', ''], 1), 'foo < bar')
+endfunction
+
+function! s:suite.three_empty_middle_right()
+  call s:assert.equals(lightline#concatenate(['foo', '', ''], 0), 'foo')
+  call s:assert.equals(lightline#concatenate(['foo', '', ''], 1), 'foo')
+endfunction
+
+function! s:suite.three_empty_left_right()
+  call s:assert.equals(lightline#concatenate(['', 'bar', ''], 0), 'bar')
+  call s:assert.equals(lightline#concatenate(['', 'bar', ''], 1), 'bar')
+endfunction
+
+function! s:suite.three_empty_left_middle()
+  call s:assert.equals(lightline#concatenate(['', '', 'baz'], 0), 'baz')
+  call s:assert.equals(lightline#concatenate(['', '', 'baz'], 1), 'baz')
+endfunction
+
+function! s:suite.three_empty_all()
+  call s:assert.equals(lightline#concatenate(['', '', ''], 0), '')
+  call s:assert.equals(lightline#concatenate(['', '', ''], 1), '')
+endfunction