added validation for models

app/models/beer.rb

@@ -4,6 +4,8 @@ class Beer < ApplicationRecord
   belongs_to :brewery
   has_many :ratings, dependent: :destroy
 
+  validates :name, presence: true
+
   def to_s
     "#{name}, #{(Brewery.find_by_id brewery_id).name}"
   end

app/models/brewery.rb

@@ -4,6 +4,11 @@ class Brewery < ApplicationRecord
   has_many :beers, dependent: :destroy
   has_many :ratings, through: :beers
 
+  validates :name, presence: true
+  validates :year, numericality: { greater_than_or_equal_to: 1040,
+                                   less_than_or_equal_to: 2023,
+                                   only_integer: true
+                                  }
   def print_report
     puts name
     puts "established at year #{year}"

app/models/rating.rb

@@ -2,6 +2,11 @@ class Rating < ApplicationRecord
   belongs_to :beer
   belongs_to :user
 
+  validates :score, numericality: { greater_than_or_equal_to: 1,
+                                    less_than_or_equal_to: 50,
+                                    only_integer: true
+                                  }
+
   def to_s
     "#{beer.name}: #{score}"
   end

app/models/user.rb

@@ -1,5 +1,7 @@
 class User < ApplicationRecord
   include RatingAverage
 
+  validates :username, uniqueness: true, length: { minimum: 3, maximum: 30 }
+
   has_many :ratings
 end