add some validations

app/models/bike.rb

@@ -1,2 +1,9 @@
 class Bike < ActiveRecord::Base
+  validates :log_number, presence: true
+  validates :brand, presence: true
+  validates :model, presence: true
+  validates :bike_type, presence: true
+  validates :color, presence: true
+  validates :frame_size, presence: true
+  validates :serial_number, presence: true
 end