diff --git a/app/models/attachment.rb b/app/models/attachment.rb
index 9807af4019c..4a9785670ac 100644
--- a/app/models/attachment.rb
+++ b/app/models/attachment.rb
@@ -29,6 +29,8 @@ class Attachment < ActiveRecord::Base
   validates_length_of :filename, :maximum => 255
   validates_length_of :disk_filename, :maximum => 255
 
+  validate :filesize_below_allowed_maximum
+
   before_save :copy_file_to_destination
   after_destroy :delete_file_on_disk
 
@@ -62,7 +64,7 @@ class Attachment < ActiveRecord::Base
   cattr_accessor :storage_path
   @@storage_path = Redmine::Configuration['attachments_storage_path'] || Rails.root.join('files').to_s
 
-  def validate
+  def filesize_below_allowed_maximum
     if self.filesize > Setting.attachment_max_size.to_i.kilobytes
       errors.add(:base, :too_long, :count => Setting.attachment_max_size.to_i.kilobytes)
     end
diff --git a/app/models/custom_field.rb b/app/models/custom_field.rb
index f7c5e2a4db6..1e08ee88731 100644
--- a/app/models/custom_field.rb
+++ b/app/models/custom_field.rb
@@ -45,6 +45,9 @@ class CustomField < ActiveRecord::Base
   validates_length_of :name, :maximum => 30
   validates_inclusion_of :field_format, :in => Redmine::CustomFieldFormat.available_formats
 
+  validate :validate_presence_of_possible_values
+  validate :validate_default_value_in_translations
+
   def initialize(attributes = nil)
     super
     self.possible_values ||= []
@@ -58,13 +61,15 @@ class CustomField < ActiveRecord::Base
     true
   end
 
-  def validate
+  def validate_presence_of_possible_values
     if self.field_format == "list"
-      errors.add(:possible_values, :blank) if self.possible_values.nil? || self.possible_values.empty?
+      errors.add(:possible_values, :blank) if self.possible_values.blank?
       errors.add(:possible_values, :invalid) unless self.possible_values.is_a? Array
     end
+  end
 
-    # validate default value in every translation available
+  # validate default value in every translation available
+  def validate_default_value_in_translations
     required_field = self.is_required
     self.is_required = false
     self.translated_locales.each do |locale|
diff --git a/app/models/custom_value.rb b/app/models/custom_value.rb
index f9dabaee910..402efeb6d14 100644
--- a/app/models/custom_value.rb
+++ b/app/models/custom_value.rb
@@ -16,6 +16,11 @@ class CustomValue < ActiveRecord::Base
   belongs_to :custom_field
   belongs_to :customized, :polymorphic => true
 
+  validate :validate_presence_of_required_value
+  validate :validate_format_of_value
+  validate :validate_type_of_value
+  validate :validate_length_of_value
+
   after_initialize :set_default_value
 
   def set_default_value
@@ -46,14 +51,19 @@ class CustomValue < ActiveRecord::Base
   end
 
 protected
-  def validate
-    if value.blank?
-      errors.add(:value, :blank) if custom_field.is_required? and value.blank?
-    else
-      errors.add(:value, :invalid) unless custom_field.regexp.blank? or value =~ Regexp.new(custom_field.regexp)
-      errors.add(:value, :too_short, :count => custom_field.min_length) if custom_field.min_length > 0 and value.length < custom_field.min_length
-      errors.add(:value, :too_long, :count => custom_field.max_length) if custom_field.max_length > 0 and value.length > custom_field.max_length
 
+  def validate_presence_of_required_value
+    errors.add(:value, :blank) if custom_field.is_required? && value.blank?
+  end
+
+  def validate_format_of_value
+    if value.present?
+      errors.add(:value, :invalid) unless custom_field.regexp.blank? or value =~ Regexp.new(custom_field.regexp)
+    end
+  end
+
+  def validate_type_of_value
+    if value.present?
       # Format specific validations
       case custom_field.field_format
       when 'int'
@@ -67,4 +77,11 @@ protected
       end
     end
   end
+
+  def validate_length_of_value
+    if value.present?
+      errors.add(:value, :too_short, :count => custom_field.min_length) if custom_field.min_length > 0 and value.length < custom_field.min_length
+      errors.add(:value, :too_long, :count => custom_field.max_length) if custom_field.max_length > 0 and value.length > custom_field.max_length
+    end
+  end
 end
diff --git a/app/models/issue.rb b/app/models/issue.rb
index b780b2a276e..0c763de75cd 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -69,6 +69,14 @@ class Issue < ActiveRecord::Base
   validates_inclusion_of :done_ratio, :in => 0..100
   validates_numericality_of :estimated_hours, :allow_nil => true
 
+  validate :validate_format_of_due_date
+  validate :validate_start_date_before_due_date
+  validate :validate_start_date_before_soonest_start_date
+  validate :validate_fixed_version_is_assignable
+  validate :validate_fixed_version_is_still_open
+  validate :validate_enabled_tracker
+  validate :validate_correct_parent
+
   scope :visible, lambda {|*args| { :include => :project,
                                     :conditions => Issue.visible_condition(args.first || User.current) } }
 
@@ -315,34 +323,44 @@ class Issue < ActiveRecord::Base
     Setting.issue_done_ratio == 'issue_field'
   end
 
-  def validate
+  def validate_format_of_due_date
     if self.due_date.nil? && @attributes['due_date'] && !@attributes['due_date'].empty?
       errors.add :due_date, :not_a_date
     end
+  end
 
+  def validate_start_date_before_due_date
     if self.due_date and self.start_date and self.due_date < self.start_date
       errors.add :due_date, :greater_than_start_date
     end
+  end
 
+  def validate_start_date_before_soonest_start_date
     if start_date && soonest_start && start_date < soonest_start
       errors.add :start_date, :invalid
     end
+  end
 
+  def validate_fixed_version_is_assignable
     if fixed_version
-      if !assignable_versions.include?(fixed_version)
-        errors.add :fixed_version_id, :inclusion
-      elsif reopened? && fixed_version.closed?
-        errors.add_to_base I18n.t(:error_can_not_reopen_issue_on_closed_version)
-      end
+      errors.add :fixed_version_id, :inclusion unless assignable_versions.include?(fixed_version)
     end
+  end
 
+  def validate_fixed_version_is_still_open
+    if fixed_version && assignable_versions.include?(fixed_version)
+      errors.add_to_base I18n.t(:error_can_not_reopen_issue_on_closed_version) if reopened? && fixed_version.closed?
+    end
+  end
+
+  def validate_enabled_tracker
     # Checks that the issue can not be added/moved to a disabled tracker
     if project && (tracker_id_changed? || project_id_changed?)
-      unless project.trackers.include?(tracker)
-        errors.add :tracker_id, :inclusion
-      end
+      errors.add :tracker_id, :inclusion unless project.trackers.include?(tracker)
     end
+  end
 
+  def validate_correct_parent
     # Checks parent issue assignment
     if @parent_issue
       if !Setting.cross_project_issue_relations? && @parent_issue.project_id != self.project_id
diff --git a/app/models/issue_relation.rb b/app/models/issue_relation.rb
index 68686f95a82..07711c5a567 100644
--- a/app/models/issue_relation.rb
+++ b/app/models/issue_relation.rb
@@ -40,11 +40,13 @@ class IssueRelation < ActiveRecord::Base
   validates_numericality_of :delay, :allow_nil => true
   validates_uniqueness_of :issue_to_id, :scope => :issue_from_id
 
+  validate :validate_sanity_of_relation
+
   before_save :update_schedule
 
   attr_protected :issue_from_id, :issue_to_id
 
-  def validate
+  def validate_sanity_of_relation
     if issue_from && issue_to
       errors.add :issue_to_id, :invalid if issue_from_id == issue_to_id
       errors.add :issue_to_id, :not_same_project unless issue_from.project_id == issue_to.project_id || Setting.cross_project_issue_relations?
diff --git a/app/models/member.rb b/app/models/member.rb
index fef7e2e0385..7f423f861db 100644
--- a/app/models/member.rb
+++ b/app/models/member.rb
@@ -24,6 +24,8 @@ class Member < ActiveRecord::Base
   validates_presence_of :principal, :project
   validates_uniqueness_of :user_id, :scope => :project_id
 
+  validate :validate_presence_of_role
+
   before_destroy :remove_from_category_assignments
   after_destroy :unwatch_from_permission_change
 
@@ -81,7 +83,7 @@ class Member < ActiveRecord::Base
 
   protected
 
-  def validate
+  def validate_presence_of_role
     errors.add_on_empty :role if member_roles.empty? && roles.empty? || !member_roles.empty? && member_roles.all?(&:marked_for_destruction?)
   end
 
diff --git a/app/models/member_role.rb b/app/models/member_role.rb
index f9d4f9b276e..4811e4c1389 100644
--- a/app/models/member_role.rb
+++ b/app/models/member_role.rb
@@ -22,8 +22,9 @@ class MemberRole < ActiveRecord::Base
   attr_protected :member_id, :role_id
 
   validates_presence_of :role
+  validate :validate_project_member_role
 
-  def validate
+  def validate_project_member_role
     errors.add :role_id, :invalid if role && !role.member?
   end
 
diff --git a/app/models/query.rb b/app/models/query.rb
index 7995f0ff0b6..ca8ac903b2c 100644
--- a/app/models/query.rb
+++ b/app/models/query.rb
@@ -25,6 +25,8 @@ class Query < ActiveRecord::Base
   validates_presence_of :name, :on => :save
   validates_length_of :name, :maximum => 255
 
+  validate :validate_filters
+
   after_initialize :remember_project_scope
 
   @@operators = { "="   => :label_equals,
@@ -91,14 +93,16 @@ class Query < ActiveRecord::Base
     @is_for_all = project.nil?
   end
 
-  def validate
+  def validate_filters
+    return unless filters
+
     filters.each_key do |field|
       errors.add label_for(field), :blank unless
           # filter requires one or more values
-          (values_for(field) and !values_for(field).first.blank?) or
+          (values_for(field) and values_for(field).first.present?) or
           # filter doesn't require any value
           ["o", "c", "!*", "*", "t", "w"].include? operator_for(field)
-    end if filters
+    end
   end
 
   def editable_by?(user)
diff --git a/app/models/time_entry.rb b/app/models/time_entry.rb
index ba96f356e90..417dfbfecef 100644
--- a/app/models/time_entry.rb
+++ b/app/models/time_entry.rb
@@ -33,6 +33,10 @@ class TimeEntry < ActiveRecord::Base
   validates_numericality_of :hours, :allow_nil => true, :message => :invalid
   validates_length_of :comments, :maximum => 255, :allow_nil => true
 
+  validate :validate_hours_are_in_range
+  validate :validate_project_is_set
+  validate :validate_consistency_of_issue_id
+
   scope :visible, lambda {|*args| {
     :include => :project,
     :conditions => Project.allowed_to_condition(args.first || User.current, :view_time_entries)
@@ -56,12 +60,6 @@ class TimeEntry < ActiveRecord::Base
     self.project ||= issue.project if issue
   end
 
-  def validate
-    errors.add :hours, :invalid if hours && (hours < 0 || hours >= 1000)
-    errors.add :project_id, :invalid if project.nil?
-    errors.add :issue_id, :invalid if (issue_id && !issue) || (issue && project!=issue.project)
-  end
-
   def hours=(h)
     write_attribute :hours, (h.is_a?(String) ? (h.to_hours || h) : h)
   end
@@ -106,4 +104,18 @@ class TimeEntry < ActiveRecord::Base
     end
     TimeEntry.maximum(:spent_on, :include => :project, :conditions => finder_conditions.conditions)
   end
+
+private
+
+  def validate_hours_are_in_range
+    errors.add :hours, :invalid if hours && (hours < 0 || hours >= 1000)
+  end
+
+  def validate_project_is_set
+    errors.add :project_id, :invalid if project.nil?
+  end
+
+  def validate_consistency_of_issue_id
+    errors.add :issue_id, :invalid if (issue_id && !issue) || (issue && project!=issue.project)
+  end
 end
diff --git a/app/models/user.rb b/app/models/user.rb
index c10b33f9e2b..87707fe4031 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -85,6 +85,8 @@ class User < Principal
   validates_confirmation_of :password, :allow_nil => true
   validates_inclusion_of :mail_notification, :in => MAIL_NOTIFICATION_OPTIONS.collect(&:first), :allow_blank => true
 
+  validate :password_not_too_short
+
   before_save :encrypt_password
   before_create :sanitize_mail_notification_setting
   before_destroy :delete_associated_public_queries
@@ -604,10 +606,11 @@ class User < Principal
 
   protected
 
-  def validate
-    # Password length validation based on setting
-    if !password.nil? && password.size < Setting.password_min_length.to_i
-      errors.add(:password, :too_short, :count => Setting.password_min_length.to_i)
+  # Password length validation based on setting
+  def password_not_too_short
+    minimum_length = Setting.password_min_length.to_i
+    if password.present? && password.size < minimum_length
+      errors.add(:password, :too_short, :count => minimum_length)
     end
   end
 
diff --git a/app/models/watcher.rb b/app/models/watcher.rb
index 32a9ab6b67b..6370090cdd3 100644
--- a/app/models/watcher.rb
+++ b/app/models/watcher.rb
@@ -21,6 +21,8 @@ class Watcher < ActiveRecord::Base
   validates_presence_of :user
   validates_uniqueness_of :user_id, :scope => [:watchable_type, :watchable_id]
 
+  validate :validate_active_user
+
   # Unwatch things that users are no longer allowed to view
   def self.prune(options={})
     if options.has_key?(:user)
@@ -36,8 +38,8 @@ class Watcher < ActiveRecord::Base
 
   protected
 
-  def validate
-    errors.add :user_id, :invalid unless user.nil? || user.active?
+  def validate_active_user
+    errors.add :user_id, :invalid if user.present? && !user.active?
   end
 
   private
diff --git a/app/models/wiki_page.rb b/app/models/wiki_page.rb
index 12a6175b8e5..6864a72d403 100644
--- a/app/models/wiki_page.rb
+++ b/app/models/wiki_page.rb
@@ -38,6 +38,10 @@ class WikiPage < ActiveRecord::Base
   validates_uniqueness_of :title, :scope => :wiki_id, :case_sensitive => false
   validates_associated :content
 
+  validate :validate_consistency_of_parent_title
+  validate :validate_non_circular_dependency
+  validate :validate_same_project
+
   after_initialize :check_and_mark_as_protected
   before_save :update_redirects
   before_destroy :remove_redirects
@@ -168,9 +172,15 @@ class WikiPage < ActiveRecord::Base
 
   protected
 
-  def validate
-    errors.add(:parent_title, :invalid) if !@parent_title.blank? && parent.nil?
+  def validate_consistency_of_parent_title
+    errors.add(:parent_title, :invalid) if @parent_title.present? && parent.nil?
+  end
+
+  def validate_non_circular_dependency
     errors.add(:parent_title, :circular_dependency) if parent && (parent == self || parent.ancestors.include?(self))
+  end
+
+  def validate_same_project
     errors.add(:parent_title, :not_same_project) if parent && (parent.wiki_id != wiki_id)
   end
 end
diff --git a/vendor/plugins/classic_pagination/test/fixtures/company.rb b/vendor/plugins/classic_pagination/test/fixtures/company.rb
index 39b55a7b315..665b0443051 100644
--- a/vendor/plugins/classic_pagination/test/fixtures/company.rb
+++ b/vendor/plugins/classic_pagination/test/fixtures/company.rb
@@ -4,7 +4,10 @@ class Company < ActiveRecord::Base
   set_sequence_name :companies_nonstd_seq
 
   validates_presence_of :name
-  def validate
+
+  validate :rating_does_not_equal_two
+
+  def rating_does_not_equal_two
     errors.add('rating', 'rating should not be 2') if rating == 2
   end  
 end
\ No newline at end of file