diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a13be3851..cea3e33d5 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -52,7 +52,9 @@ jobs:
           bundler-cache: true
  
       - name: Install system dependencies
-        run: sudo apt-get install -y libvips42 libvips-dev imagemagick
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libvips42 libvips-dev imagemagick
 
       - uses: actions/setup-node@v1
         with:
diff --git a/app/controllers/account/calculators_controller.rb b/app/controllers/account/calculators_controller.rb
index dec87775d..4a1cd4b6a 100644
--- a/app/controllers/account/calculators_controller.rb
+++ b/app/controllers/account/calculators_controller.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 class Account::CalculatorsController < Account::BaseController
-  before_action :resource, only: [:edit, :update, :destroy]
   load_and_authorize_resource
 
   def index
@@ -23,6 +22,8 @@ def new
   end
 
   def edit
+    @calculator = resource
+
     collect_fields_for_form
   end
 
@@ -37,6 +38,8 @@ def create
   end
 
   def update
+    @calculator = resource
+
     if updater
       redirect_to edit_account_calculator_path(slug: @calculator), notice: t("notifications.calculator_updated")
     else
@@ -47,6 +50,8 @@ def update
   end
 
   def destroy
+    @calculator = resource
+
     @calculator.destroy
 
     redirect_to account_calculators_path, notice: t("notifications.calculator_deleted"), status: :see_other
@@ -59,7 +64,7 @@ def collection
   end
 
   def resource
-    Calculator.find(params[:slug])
+    collection.friendly.find(params[:slug])
   end
 
   def collect_fields_for_form
diff --git a/app/controllers/api/v2/calculators_controller.rb b/app/controllers/api/v2/calculators_controller.rb
deleted file mode 100644
index d1a48a6e7..000000000
--- a/app/controllers/api/v2/calculators_controller.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-# frozen_string_literal: true
-
-class Api::V2::CalculatorsController < ApplicationController
-  def compute
-    @fields = Calculator.find_by(slug: params["id"]).fields.result
-
-    render json: @fields, root: "result", adapter: :json
-  end
-end
diff --git a/app/lib/calculation_resolver.rb b/app/lib/calculation_resolver.rb
deleted file mode 100644
index ba74bcb65..000000000
--- a/app/lib/calculation_resolver.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-# frozen_string_literal: true
-
-require "functions/items_per_month"
-require "functions/since"
-
-class CalculationResolver
-  attr_reader :calculator
-
-  def initialize
-    @calculator = Dentaku::Calculator.new
-    @calculator.add_function(:since, :numeric, Since.calculate_units)
-    @calculator.add_function(:items_per_month, :numeric, ItemsPerMonth.deferred)
-  end
-
-  def result(parameters, value)
-    calculator.evaluate(
-      value,
-      calculator.dependencies(value).index_by do |key|
-        key.to_sym
-      end.merge(parameters)
-    )
-  end
-end
diff --git a/app/lib/calculator_resolver.rb b/app/lib/calculator_resolver.rb
deleted file mode 100644
index 30777b0f1..000000000
--- a/app/lib/calculator_resolver.rb
+++ /dev/null
@@ -1,62 +0,0 @@
-# frozen_string_literal: true
-
-class CalculatorResolver
-  def self.call(calculator)
-    get_fields(calculator).each_with_object({}) do |field, hash|
-      unless field[:type] == "Calculation"
-        hash[field] = []
-
-        next
-      end
-      upcased_dependencies = upcase_dependencies(field[:value])
-      hash[field]          = all_dependent_values(upcased_dependencies)
-    end
-  end
-
-  def self.all_dependent_values(dependencies)
-    dependent_values = []
-
-    if dependent_values(dependencies).present?
-      dependent_values(dependencies).each do |value|
-        dependent_values << value
-      end
-    end
-
-    return dependent_values if dependent_calculations(dependencies).blank?
-
-    dependent_calculations(dependencies).each do |nested_calculation|
-      nested_dependencies = upcase_dependencies(nested_calculation[:value])
-      dependent_values   += all_dependent_values(nested_dependencies)
-    end
-
-    dependent_values
-  end
-
-  def self.upcase_dependencies(value)
-    selectors = CalculationResolver.new.calculator.dependencies(value)
-
-    selectors.map!(&:upcase)
-  end
-
-  def self.dependent_values(value)
-    selectors = upcase_dependencies(value)
-
-    Value.where(selector: selectors)
-  end
-
-  def self.dependent_calculations(value)
-    selectors = upcase_dependencies(value)
-
-    Calculation.where(selector: selectors)
-  end
-
-  def self.get_fields(calculator)
-    calculator.fields.result
-  end
-
-  class << self
-    private :all_dependent_values, :dependent_values,
-            :dependent_calculations, :upcase_dependencies,
-            :get_fields
-  end
-end
diff --git a/app/models/calculation.rb b/app/models/calculation.rb
deleted file mode 100644
index 3f749c47e..000000000
--- a/app/models/calculation.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-class Calculation < Field
-  validates :value, length: { minimum: 2 }
-end
diff --git a/app/models/calculator.rb b/app/models/calculator.rb
index 89a774a2a..d6e72e586 100644
--- a/app/models/calculator.rb
+++ b/app/models/calculator.rb
@@ -27,8 +27,8 @@ class Calculator < ApplicationRecord
   has_many :fields, dependent: :destroy
   has_many :formulas, dependent: :destroy
 
-  accepts_nested_attributes_for :fields, reject_if: :all_blank, allow_destroy: true
-  accepts_nested_attributes_for :formulas, reject_if: :all_blank, allow_destroy: true
+  accepts_nested_attributes_for :fields, allow_destroy: true
+  accepts_nested_attributes_for :formulas, allow_destroy: true
 
   scope :ordered_by_name, -> { order(:en_name) }
 
diff --git a/app/models/category.rb b/app/models/category.rb
index d0257c014..4aab34f78 100644
--- a/app/models/category.rb
+++ b/app/models/category.rb
@@ -24,16 +24,20 @@
 #
 class Category < ApplicationRecord
   include Translatable
+  translates :name
 
-  belongs_to :field
+  PRIORITY_RANGE = 0..10
 
-  translates :name
+  belongs_to :field, optional: true
+  has_many :diapers_periods, dependent: :destroy
+  has_many :category_categoryables, dependent: :restrict_with_exception
+
+  enum :preferable, { not_preferable: false, preferable: true }
 
   validates :uk_name, :en_name, presence: true
   validates :uk_name, :en_name,
             length: { minimum: 3, maximum: 30 },
             format: { with: /\A[\p{L}0-9\s'-]+\z/i },
-            uniqueness: { case_sensitive: false },
             allow_blank: true
   validates :priority, numericality: { greater_than_or_equal_to: 0 }
 
diff --git a/app/models/named_value.rb b/app/models/named_value.rb
deleted file mode 100644
index a31931db9..000000000
--- a/app/models/named_value.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-class NamedValue < Field
-  validates :name, length: { minimum: 2 }
-  validates :from, :to, numericality: { only_integer: true }
-end
diff --git a/app/models/range_field.rb b/app/models/range_field.rb
deleted file mode 100644
index d4bf59cf3..000000000
--- a/app/models/range_field.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-class RangeField < Field
-  validates :value, length: { minimum: 1 }
-  validates :from, :to, numericality: { only_integer: true }
-end
diff --git a/app/models/select.rb b/app/models/select.rb
deleted file mode 100644
index 9d311d04c..000000000
--- a/app/models/select.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-class Select < Field
-  validates :label, length: { minimum: 2 }
-end
diff --git a/app/models/value.rb b/app/models/value.rb
deleted file mode 100644
index 62b211561..000000000
--- a/app/models/value.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-class Value < Field
-  validates :value, format: { with: /[a-zA-Z0-9]/ }
-  validates :value, length: { minimum: 1 }
-end
diff --git a/app/serializers/field_serializer.rb b/app/serializers/field_serializer.rb
deleted file mode 100644
index 637c75cb6..000000000
--- a/app/serializers/field_serializer.rb
+++ /dev/null
@@ -1,53 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-class FieldSerializer < ActiveModel::Serializer
-  attributes :name, :result
-
-  def name
-    object.name.parameterize.underscore
-  end
-
-  # rubocop:disable Metrics/AbcSize
-  def result
-    cal_res = CalculatorResolver.call(object.calculator)
-    res     = cal_res.each_with_object({}) do |(key, value), result|
-      result[key[:value]] = value.each_with_object({}) do |v, sel|
-        sel[v[:selector].downcase] = v[:value]
-      end
-    end
-    result  = res.each_with_object({}) do |(formula, parameters), new_hash|
-      new_hash[formula] = CalculationResolver.new.result(parameters, formula)
-    end
-    answer  = result.each_with_object([]) do |(_, calculated_formula), new_array|
-      new_array << calculated_formula
-    end
-    number  = ""
-    (0..answer.count).each do |el|
-      number = answer[el] if object.selector == "R#{el + 1}"
-    end
-    number
-  end
-  # rubocop:enable Metrics/AbcSize
-end
diff --git a/db/migrate/20241119192344_change_field_in_category.rb b/db/migrate/20241119192344_change_field_in_category.rb
new file mode 100644
index 000000000..c5b85556c
--- /dev/null
+++ b/db/migrate/20241119192344_change_field_in_category.rb
@@ -0,0 +1,5 @@
+class ChangeFieldInCategory < ActiveRecord::Migration[7.2]
+  def change
+    change_column_null :categories, :field_id, true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index d530131b1..e9e42b813 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2024_11_07_140542) do
+ActiveRecord::Schema[7.2].define(version: 2024_11_19_192344) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -59,7 +59,7 @@
     t.integer "priority", default: 0, null: false
     t.string "en_name"
     t.decimal "price", precision: 10, scale: 2, default: "0.0", null: false
-    t.bigint "field_id", null: false
+    t.bigint "field_id"
     t.boolean "preferable", default: false, null: false
     t.index ["field_id"], name: "index_categories_on_field_id"
   end
diff --git a/spec/factories/calculators.rb b/spec/factories/calculators.rb
index 76607bb4b..35ede4765 100644
--- a/spec/factories/calculators.rb
+++ b/spec/factories/calculators.rb
@@ -19,6 +19,5 @@
   factory :calculator do
     en_name { "English Calculator" }
     uk_name { "Український калькуялтор" }
-    slug { "calculator" }
   end
 end
diff --git a/spec/factories/fields.rb b/spec/factories/fields.rb
index 78e5c2ec7..41e2abf45 100644
--- a/spec/factories/fields.rb
+++ b/spec/factories/fields.rb
@@ -24,7 +24,7 @@
 #
 FactoryBot.define do
   factory :field do
-    kind { 0 }
+    kind { "number" }
     en_label { "Label" }
     uk_label { "Label" }
     var_name { "var" }
diff --git a/spec/features/account/calculators_spec.rb b/spec/features/account/calculators_spec.rb
index 615a23bfb..7b57c5da3 100644
--- a/spec/features/account/calculators_spec.rb
+++ b/spec/features/account/calculators_spec.rb
@@ -3,8 +3,8 @@
 require "rails_helper"
 
 describe "visit admin page", js: true do
-  let!(:diapers_calculator) { create(:calculator, en_name: "Diapers Calculator", slug: "diapers") }
-  let!(:napkin_calculator) { create(:calculator, en_name: "Napkin Calculator", slug: "napkin") }
+  let!(:diapers_calculator) { create(:calculator, en_name: "Diapers Calculator") }
+  let!(:napkin_calculator) { create(:calculator, en_name: "Napkin Calculator") }
 
   include_context :authorize_admin
 
diff --git a/spec/features/show_calculator_spec.rb b/spec/features/show_calculator_spec.rb
index 5fe98128a..45ff97fda 100644
--- a/spec/features/show_calculator_spec.rb
+++ b/spec/features/show_calculator_spec.rb
@@ -8,20 +8,6 @@
       allow(controller).to receive(:resource).and_return(calculator)
     end
 
-    context "when result parameter is present" do
-      it "assigns @result with the value from params" do
-        get :show, params: { slug: calculator.slug, result: "42", locale: :en }
-        expect(assigns(:result)).to eq("42")
-      end
-    end
-
-    context "when result parameter is not present" do
-      it "assigns @result as nil" do
-        get :show, params: { slug: calculator.slug, locale: :en }
-        expect(assigns(:result)).to be_nil
-      end
-    end
-
     it "assigns the correct calculator to @calculator" do
       get :show, params: { slug: calculator.slug, locale: :en }
       expect(assigns(:calculator)).to eq(calculator)
diff --git a/spec/lib/calculation_resolver_spec.rb b/spec/lib/calculation_resolver_spec.rb
deleted file mode 100644
index 448eaddbb..000000000
--- a/spec/lib/calculation_resolver_spec.rb
+++ /dev/null
@@ -1,68 +0,0 @@
-# frozen_string_literal: true
-
-require "rails_helper"
-
-RSpec.describe CalculationResolver do
-  subject { described_class }
-
-  describe "#result" do
-    let(:value) { "P1 + 2" }
-    let(:parameters) { { p1: 2 } }
-    let(:calculator) { create(:calculator) }
-    let(:calculation) do
-      create(:calculation, value: value, calculator: calculator)
-    end
-
-    subject { CalculationResolver.new.result(parameters, calculation.value) }
-
-    context "when pass valid data" do
-      it { is_expected.to eq 4 }
-    end
-
-    context "when pass empty hash" do
-      let(:parameters) { {} }
-
-      it { is_expected.to be_nil }
-    end
-
-    context "when pass upcase letter in hash " do
-      let(:parameters) { { P1: 2 } }
-
-      it { is_expected.to eq 4 }
-    end
-
-    context "when pass value with `since` formula" do
-      let(:from) { Date.new(2020, 0o1, 0o1) }
-      let(:to) { Date.new(2021, 0o1, 31) }
-      let(:value) { "SINCE(#{from}, #{to}, 'day')" }
-
-      it { is_expected.to eq 396 }
-    end
-
-    context "when pass value with `items_per_month` formula" do
-      let(:value) { "ITEMS_PER_MONTH(P1, F1, F2)" }
-      let(:parameters) { { p1: 5 } }
-
-      before do
-        create(:range_field,
-               selector: "F1",
-               from: 0,
-               to: 2,
-               value: "30",
-               label: "label",
-               kind: "form",
-               calculator: calculator)
-        create(:range_field,
-               selector: "F2",
-               from: 3,
-               to: 5,
-               value: "70",
-               label: "label",
-               kind: "form",
-               calculator: calculator)
-      end
-
-      it { is_expected.to eq(300) }
-    end
-  end
-end
diff --git a/spec/lib/calculator_resolver_spec.rb b/spec/lib/calculator_resolver_spec.rb
deleted file mode 100644
index ab3af1d5e..000000000
--- a/spec/lib/calculator_resolver_spec.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-# frozen_string_literal: true
-
-require "rails_helper"
-
-RSpec.describe CalculatorResolver do
-  subject { described_class }
-
-  let(:calculator) { build(:calculator) }
-  let!(:calculation_r1) { create(:calculation, value: "P1 * P2 / P3", type: "Calculation", selector: "R1", label: "one", kind: "result", calculator: calculator) }
-  let!(:calculation_r2) { create(:calculation, value: "10 * P4", type: "Calculation", selector: "R2", label: "one", kind: "result", calculator: calculator) }
-  let!(:calculation_p4) { create(:value, value: "P1 * P5", type: "Calculation", selector: "P4", label: "four", kind: "parameter", calculator: calculator) }
-  let!(:calculation_p5) { create(:value, value: "P2 * P6", type: "Calculation", selector: "P5", label: "four", kind: "parameter", calculator: calculator) }
-  let!(:value_r3) { create(:value, value: "Value", type: "Value", selector: "R3", label: "two", kind: "result", calculator: calculator) }
-  let!(:value_p1) { create(:value, value: "Value", type: "Value", selector: "P1", label: "three", kind: "parameter", calculator: calculator) }
-  let!(:value_p2) { create(:value, value: "Value", type: "Value", selector: "P2", label: "four", kind: "parameter", calculator: calculator) }
-  let!(:value_p3) { create(:value, value: "Value", type: "Value", selector: "P3", label: "five", kind: "parameter", calculator: calculator) }
-  let!(:value_p6) { create(:value, value: "Value", type: "Value", selector: "P6", label: "six", kind: "parameter", calculator: calculator) }
-
-  describe "#call" do
-    it { expect(CalculatorResolver.call(calculator)).to be_kind_of(Hash) }
-
-    context "when 'field' is 'Calculation'" do
-      it { expect(CalculatorResolver.call(calculator)[calculation_r1]).to match_array([value_p1, value_p2, value_p3]) }
-    end
-
-    context "when 'field' is not 'Calculation'" do
-      it { expect(CalculatorResolver.call(calculator)[value_r3]).to be_empty }
-    end
-
-    context "when 'Calculation' contains deep-level nested dependecies" do
-      it { expect(CalculatorResolver.call(calculator)[calculation_r2]).to match_array([value_p1, value_p2, value_p6]) }
-    end
-  end
-end
diff --git a/spec/models/calculation_spec.rb b/spec/models/calculation_spec.rb
deleted file mode 100644
index 0fd58311a..000000000
--- a/spec/models/calculation_spec.rb
+++ /dev/null
@@ -1,43 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-require "rails_helper"
-
-RSpec.describe Calculation, type: :model do
-  let(:local_prefix_calculation) { "activerecord.errors.models.calculation.attributes" }
-
-  subject(:calculation) { create(:calculation) }
-
-  describe "validations" do
-    it { is_expected.to be_valid }
-    it {
-      is_expected.to validate_presence_of(:value).with_message(I18n
-      .t("#{local_prefix_calculation}.value.too_short"))
-    }
-    it {
-      is_expected.to validate_length_of(:value).is_at_least(2).with_message(I18n
-      .t("#{local_prefix_calculation}.value.too_short"))
-    }
-  end
-end
diff --git a/spec/models/calculator_spec.rb b/spec/models/calculator_spec.rb
index fda8d9538..6be5b5005 100644
--- a/spec/models/calculator_spec.rb
+++ b/spec/models/calculator_spec.rb
@@ -27,7 +27,6 @@
     it { is_expected.to validate_length_of(:en_name).is_at_least(3).is_at_most(50) }
     it { is_expected.to validate_presence_of(:uk_name) }
     it { is_expected.to validate_length_of(:uk_name).is_at_least(3).is_at_most(50) }
-    it { is_expected.to validate_presence_of(:slug) }
     it { is_expected.to validate_uniqueness_of(:slug) }
   end
 
@@ -35,37 +34,4 @@
     it { is_expected.to have_many(:fields).dependent(:destroy) }
     it { is_expected.to have_many(:formulas).dependent(:destroy) }
   end
-
-  describe "scope" do
-    context "finds instances by slug and name" do
-      let!(:calc) { create(:calculator, slug: "calc") }
-      let!(:calc2) { create(:calculator, slug: "diapers", name: "Calculator") }
-
-      it "finds two instances by slug or name" do
-        expect(Calculator.by_name_or_slug("calc").to_a).to include(calc, calc2)
-      end
-
-      it "returns all instances when search params are empty" do
-        expect(Calculator.by_name_or_slug("    ").to_a).to include(calc, calc2)
-      end
-
-      it "returns all instances when search params are nil" do
-        expect(Calculator.by_name_or_slug(nil).to_a).to include(calc, calc2)
-      end
-
-      it "does not find any instances" do
-        expect(Calculator.by_name_or_slug("qwerty").to_a).to eq []
-      end
-    end
-  end
-
-  describe "versioning", versioning: true do
-    let!(:calculator) { create(:calculator, name: "Calculator 1") }
-
-    it "adds a version when the calculator is updated" do
-      calculator.update!(name: "Calculator 2")
-
-      expect(calculator.versions.count).to eq(2)
-    end
-  end
 end
diff --git a/spec/models/category_spec.rb b/spec/models/category_spec.rb
index 1a8326fc8..b1c84ca96 100644
--- a/spec/models/category_spec.rb
+++ b/spec/models/category_spec.rb
@@ -32,10 +32,8 @@
   describe "validations" do
     it { is_expected.to validate_presence_of(:en_name) }
     it { is_expected.to validate_length_of(:en_name).is_at_least(3).is_at_most(30) }
-    it { is_expected.to validate_uniqueness_of(:en_name).case_insensitive }
     it { is_expected.to validate_presence_of(:uk_name) }
     it { is_expected.to validate_length_of(:uk_name).is_at_least(3).is_at_most(30) }
-    it { is_expected.to validate_uniqueness_of(:uk_name).case_insensitive }
     it { is_expected.to validate_numericality_of(:priority).is_greater_than_or_equal_to(0) }
   end
 
diff --git a/spec/models/field_spec.rb b/spec/models/field_spec.rb
index da220cd8b..076818980 100644
--- a/spec/models/field_spec.rb
+++ b/spec/models/field_spec.rb
@@ -43,7 +43,8 @@
     }
     it {
       is_expected.to define_enum_for(:kind)
-        .with_values([:number, :category])
+        .with_values(number: "number", category: "category")
+        .backed_by_column_of_type(:string)
     }
     it {
       is_expected.to define_enum_for(:unit)
@@ -87,25 +88,4 @@
   describe "associations" do
     it { is_expected.to belong_to(:calculator) }
   end
-
-  describe "#set_selector" do
-    let(:calculator) { create(:calculator) }
-    let(:field) { build(:field, label: "new", kind: 0, calculator: calculator) }
-
-    context "when there is no form fields in a database" do
-      it "generates selector with one letter and a number" do
-        expect { field.save }.to change { field.selector }.from(nil).to("F1")
-      end
-    end
-
-    context "when there are more forms fields in a database" do
-      before do
-        create(:field, label: "new", kind: 0, calculator: calculator)
-      end
-
-      it "generates selector with one letter and an increased number" do
-        expect { field.save }.to change { field.selector }.from(nil).to("F2")
-      end
-    end
-  end
 end
diff --git a/spec/models/named_value_spec.rb b/spec/models/named_value_spec.rb
deleted file mode 100644
index a96b24ef9..000000000
--- a/spec/models/named_value_spec.rb
+++ /dev/null
@@ -1,60 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-require "rails_helper"
-
-RSpec.describe NamedValue, type: :model do
-  let(:local_prefix_named_value) { "activerecord.errors.models.named_value.attributes" }
-
-  subject(:named_value) { create(:named_value) }
-
-  describe "validations" do
-    it {
-      is_expected.to validate_presence_of(:name).with_message(I18n
-        .t("#{local_prefix_named_value}.name.too_short"))
-    }
-    it {
-      is_expected.to validate_length_of(:name).is_at_least(2).with_message(I18n
-        .t("#{local_prefix_named_value}.name.too_short"))
-    }
-    it {
-      is_expected.to validate_numericality_of(:from)
-        .only_integer
-        .with_message(I18n.t("#{local_prefix_named_value}.from.not_a_number"))
-    }
-    it {
-      is_expected.to validate_numericality_of(:to)
-        .only_integer
-        .with_message(I18n.t("#{local_prefix_named_value}.to.not_an_integer"))
-    }
-    it {
-      is_expected.to validate_presence_of(:from)
-        .with_message(I18n.t("#{local_prefix_named_value}.from.not_an_integer"))
-    }
-    it {
-      is_expected.to validate_presence_of(:to)
-        .with_message(I18n.t("#{local_prefix_named_value}.to.not_an_integer"))
-    }
-  end
-end
diff --git a/spec/models/range_field_spec.rb b/spec/models/range_field_spec.rb
deleted file mode 100644
index db4c0a05e..000000000
--- a/spec/models/range_field_spec.rb
+++ /dev/null
@@ -1,61 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-require "rails_helper"
-
-RSpec.describe RangeField, type: :model do
-  let(:local_prefix_range_field) { "activerecord.errors.models.range_field.attributes" }
-
-  subject { create(:range_field) }
-
-  describe "validations" do
-    it {
-      is_expected.to validate_numericality_of(:from)
-        .only_integer
-        .with_message(I18n.t("#{local_prefix_range_field}.from.not_a_number"))
-    }
-    it {
-      is_expected.to validate_numericality_of(:to)
-        .only_integer
-        .with_message(I18n.t("#{local_prefix_range_field}.to.not_an_integer"))
-    }
-    it {
-      is_expected.to validate_length_of(:value)
-        .is_at_least(1)
-        .with_message(I18n.t("#{local_prefix_range_field}.value.too_short"))
-    }
-    it {
-      is_expected.to validate_presence_of(:from)
-        .with_message(I18n.t("#{local_prefix_range_field}.from.not_an_integer"))
-    }
-    it {
-      is_expected.to validate_presence_of(:to)
-        .with_message(I18n.t("#{local_prefix_range_field}.to.not_an_integer"))
-    }
-    it {
-      is_expected.to validate_presence_of(:value)
-        .with_message(I18n.t("#{local_prefix_range_field}.value.too_short"))
-    }
-  end
-end
diff --git a/spec/models/select_spec.rb b/spec/models/select_spec.rb
deleted file mode 100644
index af70b771a..000000000
--- a/spec/models/select_spec.rb
+++ /dev/null
@@ -1,45 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-require "rails_helper"
-
-RSpec.describe Select, type: :model do
-  describe "validations" do
-    context "with a valid label length of 2 characters" do
-      subject { build(:select, label: "ab") }
-
-      it { is_expected.to be_valid }
-    end
-
-    context "with a label of less than 2 characters" do
-      subject(:select) { build(:select, label: "a") }
-
-      it "is not valid" do
-        select.valid?
-
-        expect(select.errors[:label]).to include("is too short (minimum is 2 characters)")
-      end
-    end
-  end
-end
diff --git a/spec/models/value_spec.rb b/spec/models/value_spec.rb
deleted file mode 100644
index e961fedd2..000000000
--- a/spec/models/value_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-# frozen_string_literal: true
-
-# == Schema Information
-#
-# Table name: fields
-#
-#  id            :bigint           not null, primary key
-#  en_label      :string           default(""), not null
-#  kind          :string           not null
-#  uk_label      :string           default(""), not null
-#  unit          :integer          default("day")
-#  var_name      :string           default(""), not null
-#  created_at    :datetime         not null
-#  updated_at    :datetime         not null
-#  calculator_id :bigint           not null
-#
-# Indexes
-#
-#  index_fields_on_calculator_id  (calculator_id)
-#
-# Foreign Keys
-#
-#  fk_rails_...  (calculator_id => calculators.id)
-#
-require "rails_helper"
-
-RSpec.describe Value, type: :model do
-  let(:local_prefix_value) { "activerecord.errors.models.value.attributes" }
-
-  subject { create(:value) }
-
-  describe "validations" do
-    it { is_expected.to be_valid }
-    it {
-      is_expected.to validate_presence_of(:value).with_message(I18n
-        .t("#{local_prefix_value}.value.too_short"))
-    }
-    it { is_expected.to allow_value("Value").for(:value) }
-    it {
-      is_expected.to validate_length_of(:value).is_at_least(1).with_message(I18n
-        .t("#{local_prefix_value}.value.too_short"))
-    }
-    it {
-      is_expected.not_to allow_value(".*+/+/").for(:value).with_message(I18n
-        .t("#{local_prefix_value}.value.invalid"))
-    }
-  end
-end
diff --git a/spec/requests/calculators_spec.rb b/spec/requests/calculators_spec.rb
index dacbea773..94c13fc1b 100644
--- a/spec/requests/calculators_spec.rb
+++ b/spec/requests/calculators_spec.rb
@@ -4,61 +4,6 @@
 
 RSpec.describe CalculatorsController, type: :request do
   let(:calculator) { create(:calculator) }
-  let!(:calculation_r1) do
-    create(:calculation, value: "P1 * P2 / P3", type: "Calculation",
-                         selector: "R1", name: "First result",
-                         label: "one", kind: "result", calculator: calculator)
-  end
-  let!(:calculation_r2) do
-    create(:calculation, value: "10 * P4", type: "Calculation", selector: "R2",
-                         name: "Second result",
-                         label: "one", kind: "result", calculator: calculator)
-  end
-  let!(:calculation_p2) do
-    create(:calculation, value: "10 * P4", type: "Calculation", selector: "P2",
-                         label: "one", kind: "parameter",
-                         calculator: calculator)
-  end
-  let!(:value_r3) do
-    create(:value, value: "Value", type: "Value", selector: "R3",
-                   name: "Third result",
-                   label: "two", kind: "result", calculator: calculator)
-  end
-  let!(:value_p1) do
-    create(:value, value: "Value", type: "Value", selector: "P1",
-                   label: "three",
-                   kind: "parameter", calculator: calculator)
-  end
-  let(:json_response) { response.parsed_body }
-
-  describe "POST api/v2/calculators/PERMALINK/compute" do
-    before do
-      post compute_api_v2_calculator_path(calculator)
-    end
-
-    it "returns JSON" do
-      expect(response).to be_successful
-      expect(response.content_type).to eq("application/json; charset=utf-8")
-
-      expect(json_response).to include("result")
-      expect(json_response["result"][0]).to include("name", "result")
-    end
-
-    it "JSON response contains 'result' in the root" do
-      expect(json_response["result"]).to be_truthy
-    end
-
-    it "JSON response contains 'name' and 'result' attributes" do
-      expect(json_response["result"][0].keys).to contain_exactly(
-        "name",
-        "result"
-      )
-    end
-
-    it "JSON response contains field 'name' in snake case format" do
-      expect(json_response["result"][0]["name"]).to eq("first_result")
-    end
-  end
 
   describe "GET #index" do
     context "when show_calculators_list feature is enabled" do
@@ -113,8 +58,8 @@
   describe "POST #create" do
     include_context :authorize_admin
 
-    let(:valid_attributes) { { name: "калькулятор", slug: "test" } }
-    let(:invalid_attributes) { { name: "$калькулятор", slug: "test" } }
+    let(:valid_attributes) { { en_name: "calculator", uk_name: "калькулятор" } }
+    let(:invalid_attributes) { { en_name: "", uk_name: "" } }
 
     context "with valid attributes" do
       it "creates a calculator" do
@@ -133,7 +78,7 @@
           post account_calculators_path, params: { calculator: invalid_attributes }
         end.not_to change(Calculator, :count)
 
-        expect(response.body).to include(I18n.t("activerecord.errors.models.calculator.attributes.name.invalid"))
+        expect(response.body).to include(I18n.t("errors.messages.too_short", count: 3))
         expect(response).to render_template(:new)
       end
     end
diff --git a/spec/requests/result_calculators_spec.rb b/spec/requests/result_calculators_spec.rb
deleted file mode 100644
index 5ebc43a50..000000000
--- a/spec/requests/result_calculators_spec.rb
+++ /dev/null
@@ -1,80 +0,0 @@
-# frozen_string_literal: true
-
-require "rails_helper"
-
-RSpec.describe Api::V2::CalculatorsController, type: :request do
-  let(:calculator) { create(:calculator) }
-  let!(:value_p1) do
-    create(:value, value: "10", type: "Value", selector: "P1", label: "one",
-                   kind: "parameter",
-                   calculator: calculator)
-  end
-  let!(:value_p2) do
-    create(:value, value: "20", type: "Value", selector: "P2", label: "two",
-                   kind: "parameter",
-                   calculator: calculator)
-  end
-  let!(:value_p3) do
-    create(:value, value: "50", type: "Value", selector: "P3", label: "three",
-                   kind: "parameter",
-                   calculator: calculator)
-  end
-  let!(:value_p4) do
-    create(:value, value: "60", type: "Value", selector: "P4", label: "four",
-                   kind: "parameter",
-                   calculator: calculator)
-  end
-  let(:json_response) { response.parsed_body }
-
-  describe "POST api/v2/calculators/PERMALINK/compute" do
-    before do
-      create(:range_field, selector: "F1", from: 0, to: 3, value: "300",
-                           label: "label", kind: "form", calculator: calculator)
-      create(:range_field, selector: "F2", from: 4, to: 6, value: "240",
-                           label: "label", kind: "form", calculator: calculator)
-      create(:range_field, selector: "F3", from: 7, to: 12, value: "180",
-                           label: "label", kind: "form", calculator: calculator)
-      create(:range_field, selector: "F4", from: 13, to: 24, value: "120",
-                           label: "label", kind: "form", calculator: calculator)
-      create(:range_field, selector: "F6", from: 25, to: 30, value: "60",
-                           label: "label", kind: "form", calculator: calculator)
-      create(:value, value: "10", selector: "F7", label: "one",
-                     kind: "parameter",
-                     calculator: calculator)
-
-      create(:calculation, value: "ITEMS_PER_MONTH(P1, F1, F2, F3, F4, F5, F6)",
-                           selector: "R1", name: "Diapers amount used to date",
-                           label: "one", kind: "result", calculator: calculator)
-      create(:calculation, value: "10 + P4 ", type: "Calculation", selector: "R2",
-                           name: "Second result", label: "one", kind: "result",
-                           calculator: calculator)
-      create(:calculation, value: "10 + P2 ", type: "Calculation", selector: "R3",
-                           name: "Third result", label: "one", kind: "result",
-                           calculator: calculator)
-
-      post compute_api_v2_calculator_path(calculator)
-    end
-
-    it "http 200" do
-      expect(response.status).to eql(200)
-    end
-    it "result of calculation_r1 is 20" do
-      expect(json_response["result"][0]["result"]).to eq(2640)
-    end
-    it "result of calculation_r2 is 70" do
-      expect(json_response["result"][1]["result"]).to eq(70)
-      expect(json_response["result"][1].values).to contain_exactly(
-        "second_result", 70
-      )
-    end
-    it "result of calculation_r3 is 30" do
-      expect(json_response["result"][2]["result"]).to eq(30)
-      expect(json_response["result"][2].values).to contain_exactly(
-        "third_result", 30
-      )
-    end
-    it do
-      expect(json_response["result"][0]["result"]).to be_kind_of(Numeric)
-    end
-  end
-end