(Published via time machine. Just kidding, my blog publication tooling was broken and it took me a long time to get around to fixing it.)
When Ecto.Changeset.validate_required/3 fails, the error it adds includes not only a message but also the information [validation: :required].
This means that in tests, you can assert which validation failed and not the words in the validation message.
assert {_msg, [validation: :required]} =
changeset.errors[:name]
If you write a custom Ecto validation, your add_error/4 call can do the same.
add_error(
changeset,
:ketchup,
"insufficiently fancy",
validation: :not_fancy
)...and in the test:
assert {_msg, [validation: :not_fancy]} =
changeset.errors[:ketchup]If you do this, you can modify the human-readable message without breaking tests which simply assert whether it passed.