functests: Add some more NULL tests

test/functional/eval/null_spec.lua

@@ -40,6 +40,11 @@ describe('NULL', function()
     end)
   end
   describe('list', function()
+    -- Incorrect behaviour
+    -- FIXME Should error out with different message
+    null_test('makes :unlet act as if it is not a list', ':unlet L[0]',
+              'Vim(unlet):E689: Can only index a List or Dictionary')
+
     -- Subjectable behaviour
 
     -- FIXME Should return 1
@@ -48,6 +53,9 @@ describe('NULL', function()
     null_expr_test('is equal to empty list (reverse order)', '[] == L', 0, 0)
 
     -- Correct behaviour
+    null_expr_test('can be indexed with error message for empty list', 'L[0]',
+                   'E684: list index out of range: 0\nE15: Invalid expression: L[0]', nil)
+    null_expr_test('can be splice-indexed', 'L[:]', 0, {})
     null_expr_test('is not locked', 'islocked("v:_null_list")', 0, 0)
     null_test('is accepted by :for', 'for x in L|throw x|endfor', 0)
     null_expr_test('does not crash append()', 'append(1, L)', 0, 0, function()