How to let a snippet modify other parts of the code as well? about ultisnips HOT 4 CLOSED

global !p
def find_and_add_test(snip):
     for idx, line in enumerate(snip.buffer):
            if line.contains("register_tests"):
                break
     snip.buf[idx+1:idx+1] = ["A new line!"]
endglobal

post_expand "find_and_add_test(snip)"
snippet a "desc"
blub
endsnippet

post_expand "snip += snip.mkline(line='bla')"
snippet tt "test_action" b
endsnippet

AttributeError: 'SnippetUtilForAction' object has no attribute 'mkline'

global !p
def find_and_add_test(snip):
    vim.command("call RegisterTest(\"foo\")")
endglobal

post_expand "find_and_add_test(snip)"
snippet test "Test Function" b
void test_${1:name}(void)
{
    $0
}
endsnippet

vim.error: Vim(normal):E565: Not allowed to change text or change window)

Note: While completion [is](https://vimhelp.org/motion.txt.html#is) active [Insert](https://vimhelp.org/insert.txt.html#Insert) mode can't be used recursively and
buffer text cannot be changed.  Mappings that somehow invoke "[:normal](https://vimhelp.org/various.txt.html#%3Anormal) i.."
will generate an [E565](https://vimhelp.org/insert.txt.html#E565) error.

global !p
def find_and_add_test(name):
    vim.command(':au cursorhold <buffer> ++once call registertest('+name+')')
endglobal

post_expand "find_and_add_test(t[1])"
snippet test "test function" b
void test_${1:name}(void)
{
    $0
}
endsnippet

  File "/home/gergap/.vim/plugged/ultisnips/pythonx/UltiSnips/snippet/definition/base.py", line 195, in _eval_code
    exec(compiled_code or code, glob)
  File "<action-code>", line 1, in <module>
NameError: name 't' is not defined

global !p
def find_and_add_test(name):
    vim.command(':au cursorhold <buffer> ++once call RegisterTest("'+name+'")')
endglobal

post_jump "if snip.tabstop == 0: find_and_add_test(snip.tabstops[1].current_text)"
snippet test "test function" b
void test_${1:name}(void)
{
    $0
}
endsnippet

" name: Function name to add
function! RegisterTest(name)
    let save_pos = getpos(".")
    call search("register_tests")
    normal! j%
    exe ":normal! OUREGISTER_TEST(test_".a:name.");"
    call setpos(".", save_pos)
endfunction