Before:
  set buftype=
  silent w!

After:
  set buftype=nofile
  silent call delete('[Vader-workbench]')

Given tex (Environments: foo and bar):
  \begin{foo}
    Foo
  \end{foo}

  \begin{bar}
    Bar
  \end{bar}

Do (Change env: foo -> baz):
  csebaz\<cr>

Expect tex (Verify):
  \begin{baz}
    Foo
  \end{baz}

  \begin{bar}
    Bar
  \end{bar}

Do (Change env: foo -> bar (with completion)):
  cse\<c-z>\<c-z>\<c-z>\<cr>

Expect tex (Verify):
  \begin{bar}
    Foo
  \end{bar}

  \begin{bar}
    Bar
  \end{bar}

Before:
After: