How do I verify PostgreSQL enum constraints from Rails model test? - ruby-on-rails

Question

I am using an enum in Rails and PostgreSQL. In my model tests I usually verify that my Rails validations are backed by database constraints where appropriate (e.g. presence: true in Model and null: false in DB). I do this by deliberately making the model invalid, attempting to save it without validations and making sure it raises a ActiveRecord::StatementInvalid error.
How do I test a PostgreSQL enum from MiniTest? My usual approach isn't working as everything I try to do to set my ActiveRecord model to an invalid enum value raises an ArgumentError, even using write_attribute() directly.
Is there a way to deliberately bypass the enum restrictions in Rails? Do I need to drop down out of ActiveRecord and send an AREL or SQL query direct to the database? Is there some other approach?
# Model
class SisRecord < ApplicationRecord
enum record_type: {
student: "student",
staff: "staff",
contact: "contact"
}
validates :record_type, presence: true
end
# Migration
class CreateSisRecords < ActiveRecord::Migration[7.0]
def change
create_enum :sis_record_type, %w(student staff contact)
create_table :sis_records do |t|
t.enum :record_type, enum_type: :sis_record_type, null: false
t.timestamps
end
end
end
# Test
require "test_helper"
class SisRecordTest < ActiveSupport::TestCase
test "a record_type is required" do
record = sis_records(:valid_sis_record)
record.record_type = nil
assert_not record.save, "Saved the SIS Record without a record type"
end
test "a record_type is required by the database too" do
record = sis_records(:valid_sis_record)
record.record_type = nil
assert_raises(ActiveRecord::StatementInvalid) {
record.save(validate: false)
}
end
test "record_type is restricted to accepted values" do
accepted_values = %w(student staff contact)
record = sis_records(:valid_sis_record)
assert_nothing_raised {
record.record_type = accepted_values.sample
}
assert_raises(ArgumentError) {
record.record_type = "something else"
}
end
test "record_type is restricted to accepted values by the database too" do
accepted_values = %w(student staff contact)
record = sis_records(:valid_sis_record)
record.record_type = accepted_values.sample
assert record.save, "Record didn't save despite accepted type value '#{record.record_type}'"
record.write_attribute(:record_type, "nonsense") ### <-- ArgumentError
assert_raises(ActiveRecord::StatementInvalid) {
record.save(validate: false)
}
end
end

Answer 1

I have an answer to my own question, but I'm still open to better answers.
I found a comment on a gist that showed how to fairly simply insert a record with Arel so for now I am using this approach:
# Just the test in question
test "record_type is restricted to accepted values by the database too" do
accepted_values = %w(student staff contact)
table = Arel::Table.new(:sis_records)
manager = Arel::InsertManager.new
manager.insert [
[table[:record_type], accepted_values.sample],
[table[:created_at], Time.now],
[table[:updated_at], Time.now],
]
assert_nothing_raised {
SisRecord.connection.insert(manager.to_sql)
}
manager.insert [
[table[:record_type], "other type"],
[table[:created_at], Time.now],
[table[:updated_at], Time.now],
]
assert_raises(ActiveRecord::StatementInvalid) {
SisRecord.connection.insert(manager.to_sql)
}
end
created_at and updated_at are required fields so we have to add a value for those.
In my real case (not the simplified version I posted above), SisRecord belongs to Person so I had to provide a valid person ID (UUID) too. I did this by grabbing an ID from my people fixtures:
manager.insert [
[table[:record_type], "other type"],
[table[:person_id], people(:valid_person).id], # <--------
[table[:created_at], Time.now],
[table[:updated_at], Time.now],
]