tests: harden/fix completions with regard to longest/nvim mostly

test/completions.vim

@@ -13,6 +13,20 @@ describe 'completions'
         bd!
     end
 
+    it 'longest in completeopt'
+        " This gets set up with Vim only on VimEnter.
+        if has('nvim')
+            Expect stridx(&completeopt, 'longest') > -1
+        else
+            Expect stridx(&completeopt, 'longest') == -1
+            doautocmd VimEnter
+            Expect stridx(&completeopt, 'longest') > -1
+        endif
+
+        " Do not use it for following tests.
+        set completeopt-=longest
+    end
+
     it 'smart import'
         exec "normal ifrom os "
         Expect getline('.') == 'from os import '
@@ -35,20 +49,35 @@ describe 'completions'
     it 'exception'
         normal oIndentationErrX
         Expect getline('.') == 'IndentationError'
-        normal a().filenaX
+
+        " Do not remap keys (".") here, otherwise this triggers completion in
+        " Neovim already.
+        normal! a().filena
+
+        normal aX
         Expect getline('.') == 'IndentationError().filename'
     end
 
     it 'multi complete'
+        " NOTE: nvim results in "importErr()" here with completeopt+=longest,
+        " but Vim is fine.
+        " This is due to `pumvisible()` in jedi#complete_opened being true
+        " with nvim still, but it is 0 with Vim, i.e. Vim appears to close
+        " the pum already (with the tests).
+        "
+        " This might be a misunderstanding though, since the test might not
+        " expect the "import" keyword to be offered for completion?!
         normal oImpXErrX()
         Expect getline('.') == 'ImportError()'
     end
 
     it 'cycling through entries popup_select_first=0'
+        set completeopt+=longest
         let g:jedi#popup_select_first = 0
         execute "normal oraise impX\<C-n>"
-        " It looks like this is currently not working properly.
-        "Expect getline('.') == 'raise ImportError'
+
+        Expect getline('.') == 'raise ImportError'
+        set completeopt-=longest
     end
 
     it 'cycling through entries popup_select_first=1'
@@ -56,12 +85,27 @@ describe 'completions'
         Expect getline('.') == 'raise ImportWarning'
     end
 
-    it 'longest'
-        " -longest completes the first one
-        set completeopt -=longest
-        execute "normal oraise baseX"
-        Expect getline('.') == 'raise BaseException'
-        set completeopt +=longest
+    it 'cycling through entries popup_select_first=1 and longest'
+        set completeopt+=longest
+        execute "normal oraise impX"
+        Expect getline('.') == 'raise Import'
+
+        " With Neovim pumvisible() is 1 in jedi#complete_opened, which then
+        " triggers the <Down>.  This is not the case with Vim.
+        if has('nvim')
+            execute "normal oraise impX\<C-n>"
+            Expect getline('.') == 'raise ImportWarning'
+
+            execute "normal oraise impX\<C-n>\<C-n>"
+            Expect getline('.') == 'raise imp'
+        else
+            execute "normal oraise impX\<C-n>"
+            Expect getline('.') == 'raise ImportError'
+
+            execute "normal oraise impX\<C-n>\<C-n>"
+            Expect getline('.') == 'raise ImportWarning'
+        endif
+        set completeopt-=longest
     end
 end