patch 8.2.0023: command line editing not sufficiently tested

Problem:    Command line editing not sufficiently tested.
Solution:   Add more tests. (Dominique Pelle, closes #5374)

src/testdir/test_ex_mode.vim

@@ -0,0 +1,54 @@
+" Test editing line in Ex mode (see :help Q and :help gQ).
+
+" Helper function to test editing line in Q Ex mode
+func Ex_Q(cmd)
+  " Is there a simpler way to test editing Ex line?
+  call feedkeys("Q"
+        \    .. "let s:test_ex =<< END\<CR>"
+        \    .. a:cmd .. "\<CR>"
+        \    .. "END\<CR>"
+        \    .. "visual\<CR>", 'tx')
+  return s:test_ex[0]
+endfunc
+
+" Helper function to test editing line in gQ Ex mode
+func Ex_gQ(cmd)
+  call feedkeys("gQ" .. a:cmd .. "\<C-b>\"\<CR>", 'tx')
+  let ret = @:[1:] " Remove leading quote.
+  call feedkeys("visual\<CR>", 'tx')
+  return ret
+endfunc
+
+" Helper function to test editing line with both Q and gQ Ex mode.
+func Ex(cmd)
+ return [Ex_Q(a:cmd), Ex_gQ(a:cmd)]
+endfunc
+
+" Test editing line in Ex mode (both Q and gQ)
+func Test_ex_mode()
+  let encoding_save = &encoding
+  set sw=2
+
+  for e in ['utf8', 'latin1']
+    exe 'set encoding=' . e
+
+    call assert_equal(['bar', 'bar'],             Ex("foo bar\<C-u>bar"), e)
+    call assert_equal(["1\<C-u>2", "1\<C-u>2"],   Ex("1\<C-v>\<C-u>2"), e)
+    call assert_equal(["1\<C-b>2\<C-e>3", '213'], Ex("1\<C-b>2\<C-e>3"), e)
+    call assert_equal(['0123', '2013'],           Ex("01\<Home>2\<End>3"), e)
+    call assert_equal(['0123', '0213'],           Ex("01\<Left>2\<Right>3"), e)
+    call assert_equal(['01234', '0342'],          Ex("012\<Left>\<Left>\<Insert>3\<Insert>4"), e)
+    call assert_equal(["foo bar\<C-w>", 'foo '],  Ex("foo bar\<C-w>"), e)
+    call assert_equal(['foo', 'foo'],             Ex("fooba\<Del>\<Del>"), e)
+    call assert_equal(["foo\tbar", 'foobar'],     Ex("foo\<Tab>bar"), e)
+    call assert_equal(["abbrev\t", 'abbreviate'], Ex("abbrev\<Tab>"), e)
+    call assert_equal(['    1', "1\<C-t>\<C-t>"], Ex("1\<C-t>\<C-t>"), e)
+    call assert_equal(['  1', "1\<C-t>\<C-t>"],   Ex("1\<C-t>\<C-t>\<C-d>"), e)
+    call assert_equal(['  foo', '    foo'],       Ex("    foo\<C-d>"), e)
+    call assert_equal(['foo', '    foo0'],        Ex("    foo0\<C-d>"), e)
+    call assert_equal(['foo', '    foo^'],        Ex("    foo^\<C-d>"), e)
+  endfor
+
+  set sw&
+  let &encoding = encoding_save
+endfunc