There was something I didn't understand about form.〇〇 of form.with, so I will summarize it as a memorandum.
<%= form.text_field :title %>
An input field with a width of 20 characters is set.
<%= form.text_area :content %>
40x20 input field is set
<%= form.email.field :email %>
If @ is not included in the posted content, it will not be considered as an email address and an error will occur. Be careful when testing!
There are various other things, but this time I got an error during the test in the input field of the email, so I summarized it as a memorandum.