diff --git a/test/hierarchies.test.vim b/test/hierarchies.test.vim
new file mode 100644
index 0000000000..2592d32aa0
--- /dev/null
+++ b/test/hierarchies.test.vim
@@ -0,0 +1,172 @@
+function! Test_Call_Hierarchy()
+  call youcompleteme#test#setup#OpenFile( '/test/testdata/cpp/hierarchies.cc', {} )
+  call cursor( [ 1, 5 ] )
+
+  " Check that f's callers are present
+  function! Check1( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 4 )
+    call assert_match( '^+Function: f.*:1', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  +Function: g.*:4', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  +Function: g.*:4', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call assert_match( '^  +Function: h.*:9', getbufline( hierarchy_buf_nr, 4 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Down>\<Tab>", funcref( 'Check2' ) )
+  endfunction
+
+  " Check that g's callers are present
+  function! Check2( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 5 )
+    call assert_match( '^+Function: f.*:1', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  -Function: g.*:4', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  -Function: g.*:4', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call assert_match( '^    +Function: h.*:8', getbufline( hierarchy_buf_nr, 4 )[ 0 ] )
+    call assert_match( '^  +Function: h.*:9', getbufline( hierarchy_buf_nr, 5 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Down>\<Down>\<Tab>", funcref( 'Check3' ) )
+  endfunction
+
+  " Check that 1st h's callers are present
+  function! Check3( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 5 )
+    call assert_match( '^+Function: f.*:1', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  -Function: g.*:4', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  -Function: g.*:4', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call assert_match( '^    -Function: h.*:8', getbufline( hierarchy_buf_nr, 4 )[ 0 ] )
+    call assert_match( '^  +Function: h.*:9', getbufline( hierarchy_buf_nr, 5 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Down>\<Tab>", funcref( 'Check4' ) )
+  endfunction
+
+  " Check that 2nd h's callers are present
+  function! Check4( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 5 )
+    call assert_match( '^+Function: f.*:1', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  -Function: g.*:4', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  -Function: g.*:4', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call assert_match( '^    -Function: h.*:8', getbufline( hierarchy_buf_nr, 4 )[ 0 ] )
+    call assert_match( '^  -Function: h.*:9', getbufline( hierarchy_buf_nr, 5 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Up>\<Up>\<Up>\<Up>\<S-Tab>", funcref( 'Check5' ) )
+  endfunction
+
+  " Try to access callees of f
+  function! Check5( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 5 )
+    call assert_match( '^-Function: f.*:1', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  -Function: g.*:4', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  -Function: g.*:4', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call assert_match( '^    -Function: h.*:8', getbufline( hierarchy_buf_nr, 4 )[ 0 ] )
+    call assert_match( '^  -Function: h.*:9', getbufline( hierarchy_buf_nr, 5 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Down>\<Down>\<Down>\<Down>\<S-Tab>", funcref( 'Check6' ) )
+  endfunction
+
+  " Re-root at h
+  function! Check6( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 1 )
+    call assert_match( '^+Function: h', getbufline( hierarchy_buf_nr, 1 ) )
+    call FeedAndCheckAgain( "\<S-Tab>\<Tab>", funcref( 'Check7' ) )
+  endfunction
+
+  " Expansion after re-rooting works.
+  " NOTE: Clangd does not support outgoing calls, hence, we are stuck at just h.
+  function! Check7( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 1 )
+    call assert_match( '^-Function: h', getbufline( hierarchy_buf_nr, 1 ) )
+    call FeedAndCheckAgain( "\<C-c>", funcref( 'Check8' ) )
+  endfunction
+
+  " Make sure it is closed
+  function! Check8( id )
+    call assert_equal( len( popup_list() ), 0 )
+  endfunction
+
+  call youcompleteme#hierarchy#StartRequest( 'call' )
+  call WaitForAssert( { -> assert_equal( len( popup_list() ), 1 ) } )
+  let popup_ids = popup_list()
+  let hierarchy_win_id = popup_ids[ 0 ]
+  let hierarchy_buf_nr = winbufnr( hierarchy_win_id )
+  " Check that `+Function f` is at the start of the only line in the popup
+  call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 1 )
+  call assert_match( '^+Function: f', getbufline( hierarchy_buf_nr, 1 ) )
+  call FeedAndCheckMain( "\<Tab>", funcref( 'Check1' ) )
+endfunction
+
+function! Test_Type_Hierarchy()
+  call youcompleteme#test#setup#OpenFile( '/test/testdata/cpp/hierarchies.cc', {} )
+  call cursor( [ 13, 8 ] )
+
+  " Check that B1's subtypes are present
+  function! Check1( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 2 )
+    call assert_match( '^+Struct: B1.*:13', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  +Struct: D1.*:16', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Down>\<Tab>", funcref( 'Check2' ) )
+  endfunction
+
+  " Try to access D1's subtypes
+  function! Check2( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 2 )
+    call assert_match( '^+Struct: B1.*:13', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  -Struct: D1.*:16', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Up>\<S-Tab>", funcref( 'Check3' ) )
+  endfunction
+
+  " Check that 1st h's callers are present
+  function! Check3( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 3 )
+    call assert_match( '^  +Struct: B0.*:12', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^-Struct: B1.*:13', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  -Struct: D1.*:16', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Up>\<S-Tab>", funcref( 'Check4' ) )
+  endfunction
+
+  " Check that 2nd h's callers are present
+  function! Check4( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 3 )
+    call assert_match( '^  -Struct: B0.*:12', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^-Struct: B1.*:13', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  -Struct: D1.*:16', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Tab>", funcref( 'Check5' ) )
+  endfunction
+
+  " Re-root at B0: supertypes->subtypes
+  function! Check5( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 4 )
+    call assert_match( '^+Struct: B0.*:12', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  +Struct: B1.*:13', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  +Struct: D0.*:15', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call assert_match( '^  +Struct: D1.*:16', getbufline( hierarchy_buf_nr, 4 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Down>\<Down>\<Down>\<S-Tab>", funcref( 'Check6' ) )
+  endfunction
+
+  " Re-root at D1: subtypes->supertypes
+  function! Check6( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 3 )
+    call assert_match( '^  +Struct: B0.*:12', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^  +Struct: B1.*:13', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^+Struct: D1.*:16', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call FeedAndCheckAgain( "\<Tab>\<Up>\<S-Tab>", funcref( 'Check7' ) )
+  endfunction
+
+  " Expansion after re-rooting works.
+  function! Check7( id )
+    call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 4 )
+    call assert_match( '^  +Struct: B0.*:12', getbufline( hierarchy_buf_nr, 1 )[ 0 ] )
+    call assert_match( '^    +Struct: B0.*:12', getbufline( hierarchy_buf_nr, 2 )[ 0 ] )
+    call assert_match( '^  -Struct: B1.*:13', getbufline( hierarchy_buf_nr, 3 )[ 0 ] )
+    call assert_match( '^-Struct: D1.*:16', getbufline( hierarchy_buf_nr, 4 )[ 0 ] )
+    call FeedAndCheckAgain( "\<C-c>", funcref( 'Check7' ) )
+  endfunction
+
+  " Make sure it is closed
+  function! Check8( id )
+    call assert_equal( len( popup_list() ), 0 )
+  endfunction
+
+  call youcompleteme#hierarchy#StartRequest( 'type' )
+  call WaitForAssert( { -> assert_equal( len( popup_list() ), 1 ) } )
+  let popup_ids = popup_list()
+  let hierarchy_win_id = popup_ids[ 0 ]
+  let hierarchy_buf_nr = winbufnr( hierarchy_win_id )
+  " Check that `+Function f` is at the start of the only line in the popup
+  py3 import vim
+  call assert_equal( py3eval( 'len( vim.buffers[ ' . string( hierarchy_buf_nr ) . ' ]' ), 1 )
+  call assert_match( '^+Struct: B1', getbufline( hierarchy_buf_nr, 1 ) )
+  call FeedAndCheckMain( "\<Tab>", funcref( 'Check1' ) )
+endfunction
diff --git a/test/testdata/cpp/hierarchies.cc b/test/testdata/cpp/hierarchies.cc
new file mode 100644
index 0000000000..f2af7513de
--- /dev/null
+++ b/test/testdata/cpp/hierarchies.cc
@@ -0,0 +1,16 @@
+int f();
+
+int g() {
+    return f() + f();
+}
+
+int h() {
+    int x = g();
+    return f() + x;
+}
+
+struct B0 {};
+struct B1 : B0 {};
+
+struct D0 : B0 {};
+struct D1 : B0, B1 {};