tests: add test for Scroll autocmd

test/functional/autocmd/scroll_spec.lua

@@ -0,0 +1,24 @@
+local helpers = require('test.functional.helpers')(after_each)
+
+local clear = helpers.clear
+local eq = helpers.eq
+local eval = helpers.eval
+local funcs = helpers.funcs
+local source = helpers.source
+
+describe('Scroll', function()
+  before_each(clear)
+
+  it('is triggered by scrolling the window', function()
+    source([[
+    let g:scroll = 0
+    let g:buf = bufnr('%')
+
+    autocmd scroll * let g:scroll += 1
+
+    call nvim_buf_set_lines(g:buf, 0, -1, v:true, ['1', '2', '3', '4', '5'])
+    call feedkeys("\<C-e>", "n")
+    ]])
+    eq(1, eval('g:scroll'))
+  end)
+end)