diff --git a/spec/controllers/users_controller_spec.rb b/spec/controllers/users_controller_spec.rb
index 210d96f7ae..93058d5447 100644
--- a/spec/controllers/users_controller_spec.rb
+++ b/spec/controllers/users_controller_spec.rb
@@ -237,7 +237,7 @@ describe UsersController, type: :controller do
 
       it 'should send an email to the correct user in the correct language' do
         mail = ActionMailer::Base.deliveries.last
-        assert_not_nil mail
+        refute_nil mail
         assert_equal [registered_user.mail], mail.to
         mail.parts.each do |part|
           assert part.body.encoded.include?(I18n.t(:notice_account_activated,
diff --git a/spec/legacy/functional/activities_controller_spec.rb b/spec/legacy/functional/activities_controller_spec.rb
index 490cda52ce..888f21a941 100644
--- a/spec/legacy/functional/activities_controller_spec.rb
+++ b/spec/legacy/functional/activities_controller_spec.rb
@@ -65,7 +65,7 @@ describe ActivitiesController, type: :controller do
     get :index, id: 1, with_subprojects: 0
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:events_by_day)
+    refute_nil assigns(:events_by_day)
 
     assert_tag tag: 'h3',
                content: /#{1.day.ago.to_date.day}/,
@@ -93,7 +93,7 @@ describe ActivitiesController, type: :controller do
     get :index, id: 1, from: 3.days.ago.to_date
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:events_by_day)
+    refute_nil assigns(:events_by_day)
 
     assert_tag tag: 'h3',
                content: /#{3.day.ago.to_date.day}/,
@@ -122,7 +122,7 @@ describe ActivitiesController, type: :controller do
     get :index, user_id: 2
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:events_by_day)
+    refute_nil assigns(:events_by_day)
 
     assert_tag tag: 'h3',
                content: /#{3.day.ago.to_date.day}/,
diff --git a/spec/legacy/functional/admin_controller_spec.rb b/spec/legacy/functional/admin_controller_spec.rb
index 79ee6b63ea..9c2e631644 100644
--- a/spec/legacy/functional/admin_controller_spec.rb
+++ b/spec/legacy/functional/admin_controller_spec.rb
@@ -49,7 +49,7 @@ describe AdminController, type: :controller do
     get :projects
     assert_response :success
     assert_template 'projects'
-    assert_not_nil assigns(:projects)
+    refute_nil assigns(:projects)
     # active projects only
     assert_nil assigns(:projects).detect { |u| !u.active? }
   end
@@ -59,7 +59,7 @@ describe AdminController, type: :controller do
     assert_response :success
     assert_template 'projects'
     projects = assigns(:projects)
-    assert_not_nil projects
+    refute_nil projects
     assert_equal 1, projects.size
     assert_equal 'OnlineStore', projects.first.name
   end
diff --git a/spec/legacy/functional/boards_controller_spec.rb b/spec/legacy/functional/boards_controller_spec.rb
index 4d11a80d3e..0958d25d8b 100644
--- a/spec/legacy/functional/boards_controller_spec.rb
+++ b/spec/legacy/functional/boards_controller_spec.rb
@@ -40,8 +40,8 @@ describe BoardsController, type: :controller do
     get :index, project_id: 1
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:boards)
-    assert_not_nil assigns(:project)
+    refute_nil assigns(:boards)
+    refute_nil assigns(:project)
   end
 
   it 'should index not found' do
@@ -55,7 +55,7 @@ describe BoardsController, type: :controller do
     get :index, project_id: 1
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:topics)
+    refute_nil assigns(:topics)
   end
 
   it 'should create' do
@@ -70,18 +70,18 @@ describe BoardsController, type: :controller do
     get :show, project_id: 1, id: 1
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:board)
-    assert_not_nil assigns(:project)
-    assert_not_nil assigns(:topics)
+    refute_nil assigns(:board)
+    refute_nil assigns(:project)
+    refute_nil assigns(:topics)
   end
 
   it 'should show atom' do
     get :show, project_id: 1, id: 1, format: 'atom'
     assert_response :success
     assert_template 'common/feed'
-    assert_not_nil assigns(:board)
-    assert_not_nil assigns(:project)
-    assert_not_nil assigns(:messages)
+    refute_nil assigns(:board)
+    refute_nil assigns(:project)
+    refute_nil assigns(:messages)
   end
 
   it 'should update' do
diff --git a/spec/legacy/functional/custom_fields_controller_spec.rb b/spec/legacy/functional/custom_fields_controller_spec.rb
index 6e72cf3d83..13677a2e58 100644
--- a/spec/legacy/functional/custom_fields_controller_spec.rb
+++ b/spec/legacy/functional/custom_fields_controller_spec.rb
@@ -82,7 +82,7 @@ describe CustomFieldsController, type: :controller do
     end
     assert_redirected_to '/custom_fields?tab=WorkPackageCustomField'
     field = WorkPackageCustomField.find_by(name: 'test_post_new_list')
-    assert_not_nil field
+    refute_nil field
     assert_equal ['0.1', '0.2'], field.possible_values
     assert_equal 1, field.types.size
   end
diff --git a/spec/legacy/functional/enumerations_controller_spec.rb b/spec/legacy/functional/enumerations_controller_spec.rb
index a99e62c244..f81862ed2b 100644
--- a/spec/legacy/functional/enumerations_controller_spec.rb
+++ b/spec/legacy/functional/enumerations_controller_spec.rb
@@ -52,7 +52,7 @@ describe EnumerationsController, type: :controller do
     post :destroy, id: 4
     assert_response :success
     assert_template 'destroy'
-    assert_not_nil Enumeration.find_by(id: 4)
+    refute_nil Enumeration.find_by(id: 4)
   end
 
   it 'should destroy enumeration in use with reassignment' do
diff --git a/spec/legacy/functional/groups_controller_spec.rb b/spec/legacy/functional/groups_controller_spec.rb
index fdd0fe76d2..d406c0dd50 100644
--- a/spec/legacy/functional/groups_controller_spec.rb
+++ b/spec/legacy/functional/groups_controller_spec.rb
@@ -114,7 +114,7 @@ describe GroupsController, type: :controller do
     get :autocomplete_for_user, id: 10, q: 'mis'
     assert_response :success
     users = assigns(:users)
-    assert_not_nil users
+    refute_nil users
     assert users.any?
     assert !users.include?(Group.find(10).users.first)
   end
diff --git a/spec/legacy/functional/journals_controller_spec.rb b/spec/legacy/functional/journals_controller_spec.rb
index d75d481de8..2b1e974fd1 100644
--- a/spec/legacy/functional/journals_controller_spec.rb
+++ b/spec/legacy/functional/journals_controller_spec.rb
@@ -87,7 +87,7 @@ describe JournalsController, type: :controller do
   it 'should index' do
     get :index, project_id: 1, format: :atom
     assert_response :success
-    assert_not_nil assigns(:journals)
+    refute_nil assigns(:journals)
     assert_equal 'application/atom+xml', response.content_type
   end
 end
diff --git a/spec/legacy/functional/messages_controller_spec.rb b/spec/legacy/functional/messages_controller_spec.rb
index d2a19e2ca7..267daf60a7 100644
--- a/spec/legacy/functional/messages_controller_spec.rb
+++ b/spec/legacy/functional/messages_controller_spec.rb
@@ -42,9 +42,9 @@ describe MessagesController, type: :controller do
     get :show, board_id: 1, id: 1
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:board)
-    assert_not_nil assigns(:project)
-    assert_not_nil assigns(:topic)
+    refute_nil assigns(:board)
+    refute_nil assigns(:project)
+    refute_nil assigns(:topic)
   end
 
   it 'should show with pagination' do
@@ -60,7 +60,7 @@ describe MessagesController, type: :controller do
     assert_response :success
     assert_template 'show'
     replies = assigns(:replies)
-    assert_not_nil replies
+    refute_nil replies
     assert !replies.include?(message.children.order('id').first)
     assert replies.include?(message.children.order('id').last)
   end
@@ -95,7 +95,7 @@ describe MessagesController, type: :controller do
                   message: { subject: 'Test created message',
                              content: 'Message body' }
     message = Message.find_by(subject: 'Test created message')
-    assert_not_nil message
+    refute_nil message
     assert_redirected_to topic_path(message)
     assert_equal 'Message body', message.content
     assert_equal 2, message.author_id
diff --git a/spec/legacy/functional/my_controller_spec.rb b/spec/legacy/functional/my_controller_spec.rb
index e1624e4a6f..42109d6770 100644
--- a/spec/legacy/functional/my_controller_spec.rb
+++ b/spec/legacy/functional/my_controller_spec.rb
@@ -112,7 +112,7 @@ describe MyController, type: :controller do
       end
 
       it 'should destroy the existing token' do
-        assert_not_equal @previous_token_value, User.find(2).rss_key
+        refute_equal @previous_token_value, User.find(2).rss_key
       end
 
       it 'should create a new token' do
@@ -146,7 +146,7 @@ describe MyController, type: :controller do
       end
 
       it 'should destroy the existing token' do
-        assert_not_equal @previous_token_value, User.find(2).api_key
+        refute_equal @previous_token_value, User.find(2).api_key
       end
 
       it 'should create a new token' do
diff --git a/spec/legacy/functional/project_enumerations_controller_spec.rb b/spec/legacy/functional/project_enumerations_controller_spec.rb
index 22fbdc3859..101e43dbf6 100644
--- a/spec/legacy/functional/project_enumerations_controller_spec.rb
+++ b/spec/legacy/functional/project_enumerations_controller_spec.rb
@@ -59,7 +59,7 @@ describe ProjectEnumerationsController, type: :controller do
     assert design, 'Project activity not found'
 
     assert_equal 9, design.parent_id # Relate to the system activity
-    assert_not_equal design.parent.id, design.id # Different records
+    refute_equal design.parent.id, design.id # Different records
     assert_equal design.parent.name, design.name # Same name
     assert !design.active?
 
@@ -68,7 +68,7 @@ describe ProjectEnumerationsController, type: :controller do
     assert development, 'Project activity not found'
 
     assert_equal 10, development.parent_id # Relate to the system activity
-    assert_not_equal development.parent.id, development.id # Different records
+    refute_equal development.parent.id, development.id # Different records
     assert_equal development.parent.name, development.name # Same name
     assert development.active?
     assert_equal '0', development.custom_value_for(billable_field).value
@@ -78,7 +78,7 @@ describe ProjectEnumerationsController, type: :controller do
     assert previously_inactive, 'Project activity not found'
 
     assert_equal 14, previously_inactive.parent_id # Relate to the system activity
-    assert_not_equal previously_inactive.parent.id, previously_inactive.id # Different records
+    refute_equal previously_inactive.parent.id, previously_inactive.id # Different records
     assert_equal previously_inactive.parent.name, previously_inactive.name # Same name
     assert previously_inactive.active?
     assert_equal '1', previously_inactive.custom_value_for(billable_field).value
diff --git a/spec/legacy/functional/projects_controller_spec.rb b/spec/legacy/functional/projects_controller_spec.rb
index 102abebbe4..694c3171aa 100644
--- a/spec/legacy/functional/projects_controller_spec.rb
+++ b/spec/legacy/functional/projects_controller_spec.rb
@@ -45,7 +45,7 @@ describe ProjectsController, type: :controller do
     get :index
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:projects)
+    refute_nil assigns(:projects)
 
     assert_tag :ul, child: { tag: 'li',
                              descendant: { tag: 'a', content: 'eCookbook' },
@@ -302,14 +302,14 @@ describe ProjectsController, type: :controller do
     get :show, id: 1
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:project)
+    refute_nil assigns(:project)
   end
 
   it 'should show by identifier' do
     get :show, id: 'ecookbook'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:project)
+    refute_nil assigns(:project)
     assert_equal Project.find_by(identifier: 'ecookbook'), assigns(:project)
 
     assert_tag 'li', content: /Development status/
@@ -320,7 +320,7 @@ describe ProjectsController, type: :controller do
     get :show, id: 'ecookbook'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:project)
+    refute_nil assigns(:project)
 
     assert_no_tag 'li', content: /Development status/
   end
@@ -331,7 +331,7 @@ describe ProjectsController, type: :controller do
     get :show, id: 'ecookbook'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:project)
+    refute_nil assigns(:project)
     assert_equal Project.find_by(identifier: 'ecookbook'), assigns(:project)
   end
 
@@ -390,7 +390,7 @@ describe ProjectsController, type: :controller do
     get :destroy_info, id: 1
     assert_response :success
     assert_template 'destroy_info'
-    assert_not_nil Project.find_by(id: 1)
+    refute_nil Project.find_by(id: 1)
   end
 
   it 'should post destroy' do
diff --git a/spec/legacy/functional/repositories_controller_spec.rb b/spec/legacy/functional/repositories_controller_spec.rb
index cfda31a316..1d9b11d58f 100644
--- a/spec/legacy/functional/repositories_controller_spec.rb
+++ b/spec/legacy/functional/repositories_controller_spec.rb
@@ -60,13 +60,13 @@ describe RepositoriesController, type: :controller do
     get :revisions, project_id: 1
     assert_response :success
     assert_template 'revisions'
-    assert_not_nil assigns(:changesets)
+    refute_nil assigns(:changesets)
   end
 
   it 'should revision' do
     get :revision, project_id: 1, rev: 1
     assert_response :success
-    assert_not_nil assigns(:changeset)
+    refute_nil assigns(:changeset)
     assert_equal '1', assigns(:changeset).revision
   end
 
diff --git a/spec/legacy/functional/repositories_git_controller_spec.rb b/spec/legacy/functional/repositories_git_controller_spec.rb
index 689862f7e7..d64276c8e3 100644
--- a/spec/legacy/functional/repositories_git_controller_spec.rb
+++ b/spec/legacy/functional/repositories_git_controller_spec.rb
@@ -67,7 +67,7 @@ describe RepositoriesController, 'Git', type: :controller do
     get :show, project_id: 3
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal 10, assigns(:entries).size
     assert assigns(:entries).detect { |e| e.name == 'images' && e.kind == 'dir' }
     assert assigns(:entries).detect { |e| e.name == 'this_is_a_really_long_and_verbose_directory_name' && e.kind == 'dir' }
@@ -78,7 +78,7 @@ describe RepositoriesController, 'Git', type: :controller do
     assert assigns(:entries).detect { |e| e.name == 'renamed_test.txt' && e.kind == 'file' }
     assert assigns(:entries).detect { |e| e.name == 'filemane with spaces.txt' && e.kind == 'file' }
     assert assigns(:entries).detect { |e| e.name == ' filename with a leading space.txt ' && e.kind == 'file' }
-    assert_not_nil assigns(:changesets)
+    refute_nil assigns(:changesets)
     assigns(:changesets).size > 0
   end
 
@@ -88,13 +88,13 @@ describe RepositoriesController, 'Git', type: :controller do
     get :show, project_id: 3, rev: 'test_branch'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal 4, assigns(:entries).size
     assert assigns(:entries).detect { |e| e.name == 'images' && e.kind == 'dir' }
     assert assigns(:entries).detect { |e| e.name == 'sources' && e.kind == 'dir' }
     assert assigns(:entries).detect { |e| e.name == 'README' && e.kind == 'file' }
     assert assigns(:entries).detect { |e| e.name == 'test.txt' && e.kind == 'file' }
-    assert_not_nil assigns(:changesets)
+    refute_nil assigns(:changesets)
     assigns(:changesets).size > 0
   end
 
@@ -108,9 +108,9 @@ describe RepositoriesController, 'Git', type: :controller do
       get :show, project_id: 3, rev: t1
       assert_response :success
       assert_template 'show'
-      assert_not_nil assigns(:entries)
+      refute_nil assigns(:entries)
       assigns(:entries).size > 0
-      assert_not_nil assigns(:changesets)
+      refute_nil assigns(:changesets)
       assigns(:changesets).size > 0
     end
   end
@@ -121,13 +121,13 @@ describe RepositoriesController, 'Git', type: :controller do
     get :show, project_id: 3, path: 'images'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal ['edit.png'], assigns(:entries).map(&:name)
     entry = assigns(:entries).detect { |e| e.name == 'edit.png' }
-    assert_not_nil entry
+    refute_nil entry
     assert_equal 'file', entry.kind
     assert_equal 'images/edit.png', entry.path
-    assert_not_nil assigns(:changesets)
+    refute_nil assigns(:changesets)
     assigns(:changesets).size > 0
   end
 
@@ -137,9 +137,9 @@ describe RepositoriesController, 'Git', type: :controller do
     get :show, project_id: 3, path: 'images', rev: '7234cb2750b63f47bff735edc50a1c0a433c2518'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal ['delete.png'], assigns(:entries).map(&:name)
-    assert_not_nil assigns(:changesets)
+    refute_nil assigns(:changesets)
     assigns(:changesets).size > 0
   end
 
@@ -172,7 +172,7 @@ describe RepositoriesController, 'Git', type: :controller do
     get :entry, project_id: 3, path: 'sources'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entry)
+    refute_nil assigns(:entry)
     assert_equal 'sources', assigns(:entry).name
   end
 
@@ -203,7 +203,7 @@ describe RepositoriesController, 'Git', type: :controller do
     assert_template 'diff'
 
     diff = assigns(:diff)
-    assert_not_nil diff
+    refute_nil diff
     assert_tag tag: 'h2', content: /2f9c0091:61b685fb/
   end
 
diff --git a/spec/legacy/functional/repositories_subversion_controller_spec.rb b/spec/legacy/functional/repositories_subversion_controller_spec.rb
index 4223654aa2..e6f92721ea 100644
--- a/spec/legacy/functional/repositories_subversion_controller_spec.rb
+++ b/spec/legacy/functional/repositories_subversion_controller_spec.rb
@@ -64,8 +64,8 @@ describe RepositoriesController, 'Subversion', type: :controller do
     get :show, project_id: PRJ_ID
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entries)
-    assert_not_nil assigns(:changesets)
+    refute_nil assigns(:entries)
+    refute_nil assigns(:changesets)
   end
 
   it 'should browse root' do
@@ -74,7 +74,7 @@ describe RepositoriesController, 'Subversion', type: :controller do
     get :show, project_id: PRJ_ID
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     entry = assigns(:entries).detect { |e| e.name == 'subversion_test' }
     assert_equal 'dir', entry.kind
   end
@@ -85,7 +85,7 @@ describe RepositoriesController, 'Subversion', type: :controller do
     get :show, project_id: PRJ_ID, path: 'subversion_test'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal ['[folder_with_brackets]', 'folder', '.project', 'helloworld.c', 'textfile.txt'], assigns(:entries).map(&:name)
     entry = assigns(:entries).detect { |e| e.name == 'helloworld.c' }
     assert_equal 'file', entry.kind
@@ -99,7 +99,7 @@ describe RepositoriesController, 'Subversion', type: :controller do
     get :show, project_id: PRJ_ID, path: 'subversion_test', rev: 4
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal ['folder', '.project', 'helloworld.c', 'helloworld.rb', 'textfile.txt'], assigns(:entries).map(&:name)
   end
 
@@ -111,12 +111,12 @@ describe RepositoriesController, 'Subversion', type: :controller do
     assert_template 'changes'
 
     changesets = assigns(:changesets)
-    assert_not_nil changesets
+    refute_nil changesets
     assert_equal %w(6 3 2), changesets.map(&:revision)
 
     # svn properties displayed with svn >= 1.5 only
     if @repository.scm.client_version_above?([1, 5, 0])
-      assert_not_nil assigns(:properties)
+      refute_nil assigns(:properties)
       assert_equal 'native', assigns(:properties)['svn:eol-style']
       assert_tag :ul,
                  child: { tag: 'li',
@@ -133,7 +133,7 @@ describe RepositoriesController, 'Subversion', type: :controller do
     assert_template 'changes'
 
     changesets = assigns(:changesets)
-    assert_not_nil changesets
+    refute_nil changesets
     assert_equal %w(10 9 7 6 5 2), changesets.map(&:revision)
   end
 
@@ -191,7 +191,7 @@ describe RepositoriesController, 'Subversion', type: :controller do
     get :entry, project_id: PRJ_ID, path: 'subversion_test/folder'
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:entry)
+    refute_nil assigns(:entry)
     assert_equal 'folder', assigns(:entry).name
   end
 
@@ -281,7 +281,7 @@ describe RepositoriesController, 'Subversion', type: :controller do
     assert_template 'diff'
 
     diff = assigns(:diff)
-    assert_not_nil diff
+    refute_nil diff
     # 2 files modified
     assert_equal 2, Redmine::UnifiedDiff.new(diff).size
 
diff --git a/spec/legacy/functional/roles_controller_spec.rb b/spec/legacy/functional/roles_controller_spec.rb
index 13cc3a9235..4bb5f6082a 100644
--- a/spec/legacy/functional/roles_controller_spec.rb
+++ b/spec/legacy/functional/roles_controller_spec.rb
@@ -44,7 +44,7 @@ describe RolesController, type: :controller do
     assert_response :success
     assert_template 'index'
 
-    assert_not_nil assigns(:roles)
+    refute_nil assigns(:roles)
     assert_equal Role.order('builtin, position').to_a, assigns(:roles)
 
     assert_tag tag: 'a', attributes: { href: edit_role_path(1) },
@@ -74,7 +74,7 @@ describe RolesController, type: :controller do
 
     assert_redirected_to roles_path
     role = Role.find_by(name: 'RoleWithoutWorkflowCopy')
-    assert_not_nil role
+    refute_nil role
     assert_equal [:add_work_packages, :edit_work_packages, :log_time], role.permissions
     assert !role.assignable?
   end
@@ -87,7 +87,7 @@ describe RolesController, type: :controller do
 
     assert_redirected_to roles_path
     role = Role.find_by(name: 'RoleWithWorkflowCopy')
-    assert_not_nil role
+    refute_nil role
     assert_equal Role.find(1).workflows.size, role.workflows.size
   end
 
@@ -122,7 +122,7 @@ describe RolesController, type: :controller do
     delete :destroy, id: 1
     assert_redirected_to roles_path
     assert flash[:error] == 'This role is in use and cannot be deleted.'
-    assert_not_nil Role.find_by(id: 1)
+    refute_nil Role.find_by(id: 1)
   end
 
   it 'should get report' do
@@ -130,7 +130,7 @@ describe RolesController, type: :controller do
     assert_response :success
     assert_template 'report'
 
-    assert_not_nil assigns(:roles)
+    refute_nil assigns(:roles)
     assert_equal Role.order('builtin, position'), assigns(:roles)
 
     assert_tag tag: 'input', attributes: { type: 'checkbox',
diff --git a/spec/legacy/functional/search_controller_spec.rb b/spec/legacy/functional/search_controller_spec.rb
index 91661c2d2b..350cc2ac28 100644
--- a/spec/legacy/functional/search_controller_spec.rb
+++ b/spec/legacy/functional/search_controller_spec.rb
@@ -67,7 +67,7 @@ describe SearchController, type: :controller do
     get :index, project_id: 1
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:project)
+    refute_nil assigns(:project)
 
     get :index, project_id: 1, q: 'can'
     assert_response :success
@@ -78,7 +78,7 @@ describe SearchController, type: :controller do
     get :index, project_id: 1, q: 'stringforcustomfield'
     assert_response :success
     results = assigns(:results)
-    assert_not_nil results
+    refute_nil results
     assert_equal 1, results.size
     assert results.include?(WorkPackage.find(7))
   end
@@ -87,7 +87,7 @@ describe SearchController, type: :controller do
     # 'all words' is on by default
     get :index, project_id: 1, q: 'recipe updating saving'
     results = assigns(:results)
-    assert_not_nil results
+    refute_nil results
     assert_equal 1, results.size
     assert results.include?(WorkPackage.find(3))
   end
@@ -95,7 +95,7 @@ describe SearchController, type: :controller do
   it 'should search one of the words' do
     get :index, project_id: 1, q: 'recipe updating saving', submit: 'Search'
     results = assigns(:results)
-    assert_not_nil results
+    refute_nil results
     assert_equal 3, results.size
     assert results.include?(WorkPackage.find(3))
   end
@@ -103,14 +103,14 @@ describe SearchController, type: :controller do
   it 'should search titles only without result' do
     get :index, project_id: 1, q: 'recipe updating saving', all_words: '1', titles_only: '1', submit: 'Search'
     results = assigns(:results)
-    assert_not_nil results
+    refute_nil results
     assert_equal 0, results.size
   end
 
   it 'should search titles only' do
     get :index, project_id: 1, q: 'recipe', titles_only: '1', submit: 'Search'
     results = assigns(:results)
-    assert_not_nil results
+    refute_nil results
     assert_equal 2, results.size
   end
 
diff --git a/spec/legacy/functional/time_entries/reports_controller_spec.rb b/spec/legacy/functional/time_entries/reports_controller_spec.rb
index 9ca3b9ab63..7d006725a5 100644
--- a/spec/legacy/functional/time_entries/reports_controller_spec.rb
+++ b/spec/legacy/functional/time_entries/reports_controller_spec.rb
@@ -63,7 +63,7 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, columns: 'week', from: '2007-04-01', to: '2007-04-30', criterias: ['project']
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '8.65', '%.2f' % assigns(:total_hours)
   end
 
@@ -71,7 +71,7 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, project_id: 1, criterias: ['project', 'issue']
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '162.90', '%.2f' % assigns(:total_hours)
   end
 
@@ -79,7 +79,7 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, project_id: 1, criterias: ['project', 'issue'], columns: 'day'
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '162.90', '%.2f' % assigns(:total_hours)
     assert_tag tag: 'th', content: '2007-03-12'
   end
@@ -88,7 +88,7 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, project_id: 1, columns: 'week', from: '2007-04-01', to: '2007-04-30', criterias: ['project']
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '8.65', '%.2f' % assigns(:total_hours)
   end
 
@@ -96,7 +96,7 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, project_id: 1, columns: 'month', from: '2007-01-01', to: '2007-12-31', criterias: ['member', 'activity']
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '162.90', '%.2f' % assigns(:total_hours)
   end
 
@@ -104,7 +104,7 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, project_id: 1, columns: 'day', from: '2007-03-23', to: '2007-03-23', criterias: ['member', 'activity']
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '4.25', '%.2f' % assigns(:total_hours)
   end
 
@@ -112,7 +112,7 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, project_id: 1, work_package_id: 1, columns: 'month', from: '2007-01-01', to: '2007-12-31', criterias: ['member', 'activity']
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '154.25', '%.2f' % assigns(:total_hours)
     assert_tag :form,
                attributes: { action: work_package_time_entries_report_path(1), id: 'query_form' }
@@ -122,8 +122,8 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, project_id: 1, criterias: ['project', 'cf_1', 'cf_7']
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
-    assert_not_nil assigns(:criterias)
+    refute_nil assigns(:total_hours)
+    refute_nil assigns(:criterias)
     assert_equal 3, assigns(:criterias).size
     assert_equal '162.90', '%.2f' % assigns(:total_hours)
     # Custom field column
@@ -141,7 +141,7 @@ describe TimeEntries::ReportsController, type: :controller do
     get :show, project_id: 1, columns: 'week', from: '1998-04-01', to: '1998-04-30', criterias: ['project']
     assert_response :success
     assert_template 'time_entries/reports/show'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '0.00', '%.2f' % assigns(:total_hours)
   end
 
diff --git a/spec/legacy/functional/timelog_controller_spec.rb b/spec/legacy/functional/timelog_controller_spec.rb
index 93d9ec6f61..438b525ab7 100644
--- a/spec/legacy/functional/timelog_controller_spec.rb
+++ b/spec/legacy/functional/timelog_controller_spec.rb
@@ -90,7 +90,7 @@ describe TimelogController, type: :controller do
 
     i = WorkPackage.find(1)
     t = TimeEntry.find_by(comments: 'Some work on TimelogControllerTest')
-    assert_not_nil t
+    refute_nil t
     assert_equal 11, t.activity_id
     assert_equal 7.3, t.hours
     assert_equal 3, t.user_id
@@ -112,7 +112,7 @@ describe TimelogController, type: :controller do
     assert_redirected_to action: 'index', project_id: 'ecookbook'
 
     t = TimeEntry.find_by(comments: 'Some work on TimelogControllerTest')
-    assert_not_nil t
+    refute_nil t
     assert_equal 11, t.activity_id
     assert_equal 7.3, t.hours
     assert_equal 3, t.user_id
@@ -154,7 +154,7 @@ describe TimelogController, type: :controller do
     delete :destroy, id: 1
     assert_redirected_to action: 'index', project_id: 'ecookbook'
     assert_equal I18n.t(:notice_unable_delete_time_entry), flash[:error]
-    assert_not_nil TimeEntry.find_by(id: 1)
+    refute_nil TimeEntry.find_by(id: 1)
 
     # remove the simulation
     TimeEntry._destroy_callbacks.reject! { |callback| callback.filter == :stop_callback_chain }
@@ -164,7 +164,7 @@ describe TimelogController, type: :controller do
     get :index
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '162.90', '%.2f' % assigns(:total_hours)
     assert_tag :form,
                attributes: { action: '/time_entries', id: 'query_form' }
@@ -174,11 +174,11 @@ describe TimelogController, type: :controller do
     get :index, project_id: 'ecookbook'
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal 4, assigns(:entries).size
     # project and subproject
     assert_equal [1, 3], assigns(:entries).map(&:project_id).uniq.sort
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '162.90', '%.2f' % assigns(:total_hours)
     # display all time by default
     assert_equal '2007-03-12'.to_date, assigns(:from)
@@ -191,9 +191,9 @@ describe TimelogController, type: :controller do
     get :index, project_id: 'ecookbook', from: '2007-03-20', to: '2007-04-30'
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal 3, assigns(:entries).size
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '12.90', '%.2f' % assigns(:total_hours)
     assert_equal '2007-03-20'.to_date, assigns(:from)
     assert_equal '2007-04-30'.to_date, assigns(:to)
@@ -205,8 +205,8 @@ describe TimelogController, type: :controller do
     get :index, project_id: 'ecookbook', period: '7_days'
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:entries)
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:entries)
+    refute_nil assigns(:total_hours)
     assert_equal Date.today - 7, assigns(:from)
     assert_equal Date.today, assigns(:to)
     assert_tag :form,
@@ -217,7 +217,7 @@ describe TimelogController, type: :controller do
     get :index, project_id: 'ecookbook', from: '2007-03-23', to: '2007-03-23'
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal '4.25', '%.2f' % assigns(:total_hours)
     assert_tag :form,
                attributes: { action: '/projects/ecookbook/time_entries', id: 'query_form' }
@@ -227,9 +227,9 @@ describe TimelogController, type: :controller do
     get :index, work_package_id: 1
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:entries)
+    refute_nil assigns(:entries)
     assert_equal 2, assigns(:entries).size
-    assert_not_nil assigns(:total_hours)
+    refute_nil assigns(:total_hours)
     assert_equal 154.25, assigns(:total_hours)
     # display all time based on what's been logged
     assert_equal '2007-03-12'.to_date, assigns(:from)
@@ -244,7 +244,7 @@ describe TimelogController, type: :controller do
     get :index, project_id: 1, format: 'atom'
     assert_response :success
     assert_equal 'application/atom+xml', response.content_type
-    assert_not_nil assigns(:items)
+    refute_nil assigns(:items)
     assert assigns(:items).first.is_a?(TimeEntry)
   end
 end
diff --git a/spec/legacy/functional/types_controller_spec.rb b/spec/legacy/functional/types_controller_spec.rb
index 0585a1f2ed..d6716233df 100644
--- a/spec/legacy/functional/types_controller_spec.rb
+++ b/spec/legacy/functional/types_controller_spec.rb
@@ -122,6 +122,6 @@ describe TypesController, type: :controller do
       post :destroy, id: 1
     end
     assert_redirected_to action: 'index'
-    assert_not_nil flash[:error]
+    refute_nil flash[:error]
   end
 end
diff --git a/spec/legacy/functional/user_mailer_spec.rb b/spec/legacy/functional/user_mailer_spec.rb
index da90c82b15..7e011b81a7 100644
--- a/spec/legacy/functional/user_mailer_spec.rb
+++ b/spec/legacy/functional/user_mailer_spec.rb
@@ -203,7 +203,7 @@ describe UserMailer, type: :mailer do
     issue = FactoryGirl.create(:work_package)
     mail = UserMailer.work_package_added(user, issue.journals.first, user)
     assert mail.deliver
-    assert_not_nil mail
+    refute_nil mail
     assert_equal 'bulk', mail.header['Precedence'].to_s
     assert_equal 'auto-generated', mail.header['Auto-Submitted'].to_s
   end
@@ -236,7 +236,7 @@ describe UserMailer, type: :mailer do
       UserMailer.test_mail(user).deliver
     end
     mail = ActionMailer::Base.deliveries.last
-    assert_not_nil mail
+    refute_nil mail
     assert_equal 'Redmine app <redmine@example.net>', mail.header['From'].to_s
   end
 
@@ -266,7 +266,7 @@ describe UserMailer, type: :mailer do
     issue = FactoryGirl.create(:work_package)
     mail = UserMailer.work_package_added(user, issue.journals.first, user)
     mail.deliver
-    assert_not_nil mail
+    refute_nil mail
     assert_equal UserMailer.generate_message_id(issue, user), mail.message_id
     assert_nil mail.references
   end
@@ -277,7 +277,7 @@ describe UserMailer, type: :mailer do
     journal = issue.journals.first
     UserMailer.work_package_updated(user, journal).deliver
     mail = ActionMailer::Base.deliveries.last
-    assert_not_nil mail
+    refute_nil mail
     assert_equal UserMailer.generate_message_id(journal, user), mail.message_id
     assert_match mail.references, UserMailer.generate_message_id(journal.journable, user)
   end
@@ -287,7 +287,7 @@ describe UserMailer, type: :mailer do
     message = FactoryGirl.create(:message)
     UserMailer.message_posted(user, message, user).deliver
     mail = ActionMailer::Base.deliveries.last
-    assert_not_nil mail
+    refute_nil mail
     assert_equal UserMailer.generate_message_id(message, user), mail.message_id
     assert_nil mail.references
     assert_select_email do
@@ -302,7 +302,7 @@ describe UserMailer, type: :mailer do
     message = FactoryGirl.create(:message, parent: parent)
     UserMailer.message_posted(user, message, user).deliver
     mail = ActionMailer::Base.deliveries.last
-    assert_not_nil mail
+    refute_nil mail
     assert_equal UserMailer.generate_message_id(message, user), mail.message_id
     assert_match mail.references, UserMailer.generate_message_id(parent, user)
     assert_select_email do
@@ -465,7 +465,7 @@ describe UserMailer, type: :mailer do
 
   def last_email
     mail = ActionMailer::Base.deliveries.last
-    assert_not_nil mail
+    refute_nil mail
     mail
   end
 
diff --git a/spec/legacy/functional/users_controller_spec.rb b/spec/legacy/functional/users_controller_spec.rb
index 5ac0aca13a..178d9a0bce 100644
--- a/spec/legacy/functional/users_controller_spec.rb
+++ b/spec/legacy/functional/users_controller_spec.rb
@@ -50,7 +50,7 @@ describe UsersController, type: :controller do
     get :index
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:users)
+    refute_nil assigns(:users)
     # active users only
     assert_nil assigns(:users).detect { |u| !u.active? }
   end
@@ -60,7 +60,7 @@ describe UsersController, type: :controller do
     assert_response :success
     assert_template 'index'
     users = assigns(:users)
-    assert_not_nil users
+    refute_nil users
     assert_equal 1, users.size
     assert_equal 'John', users.first.firstname
   end
@@ -80,7 +80,7 @@ describe UsersController, type: :controller do
     get :show, id: 2
     assert_response :success
     assert_template 'show'
-    assert_not_nil assigns(:user)
+    refute_nil assigns(:user)
 
     assert_no_tag 'li', content: /Phone number/
   end
@@ -112,7 +112,7 @@ describe UsersController, type: :controller do
     session[:user_id] = 1
     get :show, id: 5
     assert_response 200
-    assert_not_nil assigns(:user)
+    refute_nil assigns(:user)
   end
 
   it 'should show displays memberships based on project visibility' do
@@ -120,7 +120,7 @@ describe UsersController, type: :controller do
     get :show, id: 2
     assert_response :success
     memberships = assigns(:memberships)
-    assert_not_nil memberships
+    refute_nil memberships
     project_ids = memberships.map(&:project_id)
     assert project_ids.include?(2) # private project admin can see
   end
@@ -177,7 +177,7 @@ describe UsersController, type: :controller do
     assert user.check_password?('adminADMIN!')
 
     mail = ActionMailer::Base.deliveries.last
-    assert_not_nil mail
+    refute_nil mail
     assert_equal [user.mail], mail.to
     assert mail.body.encoded.include?('adminADMIN!')
   end
@@ -227,7 +227,7 @@ describe UsersController, type: :controller do
     assert u.check_password?('newpassPASS!')
 
     mail = ActionMailer::Base.deliveries.last
-    assert_not_nil mail
+    refute_nil mail
     assert_equal [u.mail], mail.to
     assert mail.body.encoded.include?('newpassPASS!')
   end
diff --git a/spec/legacy/functional/welcome_controller_spec.rb b/spec/legacy/functional/welcome_controller_spec.rb
index b1f832673e..7fefd6884d 100644
--- a/spec/legacy/functional/welcome_controller_spec.rb
+++ b/spec/legacy/functional/welcome_controller_spec.rb
@@ -43,8 +43,8 @@ describe WelcomeController, type: :controller do
     get :index
     assert_response :success
     assert_template 'index'
-    assert_not_nil assigns(:news)
-    assert_not_nil assigns(:projects)
+    refute_nil assigns(:news)
+    refute_nil assigns(:projects)
     assert !assigns(:projects).include?(Project.where(is_public: false).first)
   end
 
diff --git a/spec/legacy/functional/wiki_controller_spec.rb b/spec/legacy/functional/wiki_controller_spec.rb
index d70aa567db..90e087c477 100644
--- a/spec/legacy/functional/wiki_controller_spec.rb
+++ b/spec/legacy/functional/wiki_controller_spec.rb
@@ -102,7 +102,7 @@ describe WikiController, type: :controller do
     assert_redirected_to action: 'show', project_id: 'ecookbook', id: 'New_page'
     page = wiki.find_page('New page')
     assert !page.new_record?
-    assert_not_nil page.content
+    refute_nil page.content
     assert_equal 'Created the page', page.content.last_journal.notes
   end
 
@@ -233,7 +233,7 @@ describe WikiController, type: :controller do
     get :history, project_id: 1, id: 'CookBook_documentation'
     assert_response :success
     assert_template 'history'
-    assert_not_nil assigns(:versions)
+    refute_nil assigns(:versions)
     assert_equal 3, assigns(:versions).size
     assert_select 'input[type=submit][name=commit]'
   end
@@ -246,7 +246,7 @@ describe WikiController, type: :controller do
     get :history, project_id: 1, id: 'Another_page'
     assert_response :success
     assert_template 'history'
-    assert_not_nil assigns(:versions)
+    refute_nil assigns(:versions)
     assert_equal 1, assigns(:versions).size
     assert_select 'input[type=submit][name=commit]', false
   end
@@ -312,7 +312,7 @@ describe WikiController, type: :controller do
                            redirect_existing_links: 1 }
     assert_redirected_to action: 'show', project_id: 'ecookbook', id: 'Another_renamed_page'
     # Check redirects
-    assert_not_nil wiki.find_page('Another page')
+    refute_nil wiki.find_page('Another page')
     assert_nil wiki.find_page('Another page', with_redirect: false)
   end
 
@@ -375,7 +375,7 @@ describe WikiController, type: :controller do
     assert_response :success
     assert_template 'index'
     pages = assigns(:pages)
-    assert_not_nil pages
+    refute_nil pages
     assert_equal wiki.pages.size, pages.size
     assert_equal pages.first.content.updated_on, pages.first.updated_on
 
diff --git a/spec/legacy/functional/wikis_controller_spec.rb b/spec/legacy/functional/wikis_controller_spec.rb
index e3de5df3b0..502c997c17 100644
--- a/spec/legacy/functional/wikis_controller_spec.rb
+++ b/spec/legacy/functional/wikis_controller_spec.rb
@@ -42,7 +42,7 @@ describe WikisController, type: :controller do
     post :edit, id: 3, wiki: { start_page: 'Start page' }
     assert_response :success
     wiki = Project.find(3).wiki
-    assert_not_nil wiki
+    refute_nil wiki
     assert_equal 'Start page', wiki.start_page
   end
 
diff --git a/spec/legacy/functional/workflows_controller_spec.rb b/spec/legacy/functional/workflows_controller_spec.rb
index 1c662d3241..43484aa8b7 100644
--- a/spec/legacy/functional/workflows_controller_spec.rb
+++ b/spec/legacy/functional/workflows_controller_spec.rb
@@ -53,8 +53,8 @@ describe WorkflowsController, type: :controller do
     get :edit
     assert_response :success
     assert_template 'edit'
-    assert_not_nil assigns(:roles)
-    assert_not_nil assigns(:types)
+    refute_nil assigns(:roles)
+    refute_nil assigns(:types)
   end
 
   it 'should get edit with role and type' do
@@ -67,7 +67,7 @@ describe WorkflowsController, type: :controller do
     assert_template 'edit'
 
     # used status only
-    assert_not_nil assigns(:statuses)
+    refute_nil assigns(:statuses)
     assert_equal [2, 3, 5], assigns(:statuses).map(&:id)
 
     # allowed transitions
@@ -92,7 +92,7 @@ describe WorkflowsController, type: :controller do
     assert_response :success
     assert_template 'edit'
 
-    assert_not_nil assigns(:statuses)
+    refute_nil assigns(:statuses)
     assert_equal Status.count, assigns(:statuses).size
 
     assert_tag tag: 'input', attributes: { type: 'checkbox',
@@ -110,7 +110,7 @@ describe WorkflowsController, type: :controller do
     assert_redirected_to '/workflows/edit?role_id=2&type_id=1'
 
     assert_equal 3, Workflow.where(type_id: 1, role_id: 2).count
-    assert_not_nil Workflow.where(role_id: 2, type_id: 1, old_status_id: 3, new_status_id: 2).first
+    refute_nil Workflow.where(role_id: 2, type_id: 1, old_status_id: 3, new_status_id: 2).first
     assert_nil Workflow.where(role_id: 2, type_id: 1, old_status_id: 5, new_status_id: 4).first
   end
 
diff --git a/spec/legacy/unit/activity_spec.rb b/spec/legacy/unit/activity_spec.rb
index a03ecfe87d..74404663fc 100644
--- a/spec/legacy/unit/activity_spec.rb
+++ b/spec/legacy/unit/activity_spec.rb
@@ -49,7 +49,7 @@ describe Activity, type: :model do
 
   it 'should activity without subprojects' do
     events = find_events(User.anonymous, project: @project)
-    assert_not_nil events
+    refute_nil events
 
     assert events.include?(WorkPackage.find(1))
     assert !events.include?(WorkPackage.find(4))
@@ -59,7 +59,7 @@ describe Activity, type: :model do
 
   it 'should activity with subprojects' do
     events = find_events(User.anonymous, project: @project, with_subprojects: 1)
-    assert_not_nil events
+    refute_nil events
 
     assert events.include?(WorkPackage.find(1))
     # subproject issue
@@ -68,7 +68,7 @@ describe Activity, type: :model do
 
   it 'should global activity anonymous' do
     events = find_events(User.anonymous)
-    assert_not_nil events
+    refute_nil events
 
     assert events.include?(WorkPackage.find(1))
     assert events.include?(Message.find(5))
@@ -78,7 +78,7 @@ describe Activity, type: :model do
 
   it 'should global activity logged user' do
     events = find_events(User.find(2)) # manager
-    assert_not_nil events
+    refute_nil events
 
     assert events.include?(WorkPackage.find(1))
     # Issue of a private project the user belongs to
diff --git a/spec/legacy/unit/journal_spec.rb b/spec/legacy/unit/journal_spec.rb
index 260696ff8a..bff34ded1d 100644
--- a/spec/legacy/unit/journal_spec.rb
+++ b/spec/legacy/unit/journal_spec.rb
@@ -95,7 +95,7 @@ describe Journal, type: :model do
       @issue.save
     end
 
-    assert_not_equal start, @issue.reload.updated_at
+    refute_equal start, @issue.reload.updated_at
   end
 
   specify 'accessing #journaled on a Journal should not error (parent class)' do
diff --git a/spec/legacy/unit/lib/redmine/i18n_spec.rb b/spec/legacy/unit/lib/redmine/i18n_spec.rb
index caf7333961..1dc2091534 100644
--- a/spec/legacy/unit/lib/redmine/i18n_spec.rb
+++ b/spec/legacy/unit/lib/redmine/i18n_spec.rb
@@ -58,8 +58,8 @@ describe Redmine::I18n do
         format_date(Date.today)
         format_time(Time.now)
         format_time(Time.now, false)
-        assert_not_equal 'default', ::I18n.l(Date.today, format: :default), "date.formats.default missing in #{lang}"
-        assert_not_equal 'time',    ::I18n.l(Time.now, format: :time),      "time.formats.time missing in #{lang}"
+        refute_equal 'default', ::I18n.l(Date.today, format: :default), "date.formats.default missing in #{lang}"
+        refute_equal 'time',    ::I18n.l(Time.now, format: :time),      "time.formats.time missing in #{lang}"
       end
       assert l('date.day_names').is_a?(Array)
       assert_equal 7, l('date.day_names').size
diff --git a/spec/legacy/unit/lib/redmine/menu_manager/mapper_spec.rb b/spec/legacy/unit/lib/redmine/menu_manager/mapper_spec.rb
index c664fb3d7b..7bb9a8c1d1 100644
--- a/spec/legacy/unit/lib/redmine/menu_manager/mapper_spec.rb
+++ b/spec/legacy/unit/lib/redmine/menu_manager/mapper_spec.rb
@@ -72,7 +72,7 @@ describe Redmine::MenuManager::Mapper do
     root = menu_mapper.find(:root)
     assert_equal 5, root.children.size
     { 0 => :test_first, 1 => :test_second, 2 => :test_third, 3 => :test_fourth, 4 => :test_fifth }.each do |position, name|
-      assert_not_nil root.children[position]
+      refute_nil root.children[position]
       assert_equal name, root.children[position].name
     end
   end
@@ -88,7 +88,7 @@ describe Redmine::MenuManager::Mapper do
     root = menu_mapper.find(:root)
     assert_equal 5, root.children.size
     { 0 => :test_first, 1 => :test_second, 2 => :test_third, 3 => :test_fourth, 4 => :test_fifth }.each do |position, name|
-      assert_not_nil root.children[position]
+      refute_nil root.children[position]
       assert_equal name, root.children[position].name
     end
   end
@@ -104,7 +104,7 @@ describe Redmine::MenuManager::Mapper do
     root = menu_mapper.find(:root)
     assert_equal 5, root.children.size
     { 0 => :test_first, 1 => :test_second, 2 => :test_third, 3 => :test_fourth, 4 => :test_fifth }.each do |position, name|
-      assert_not_nil root.children[position]
+      refute_nil root.children[position]
       assert_equal name, root.children[position].name
     end
   end
@@ -120,7 +120,7 @@ describe Redmine::MenuManager::Mapper do
     root = menu_mapper.find(:root)
     assert_equal 5, root.children.size
     { 0 => :test_first, 1 => :test_second, 2 => :test_third, 3 => :test_fourth, 4 => :test_fifth }.each do |position, name|
-      assert_not_nil root.children[position]
+      refute_nil root.children[position]
       assert_equal name, root.children[position].name
     end
   end
@@ -160,7 +160,7 @@ describe Redmine::MenuManager::Mapper do
   it 'should delete' do
     menu_mapper = Redmine::MenuManager::Mapper.new(:test_menu, {})
     menu_mapper.push :test_overview, { controller: 'projects', action: 'show' }, {}
-    assert_not_nil menu_mapper.delete(:test_overview)
+    refute_nil menu_mapper.delete(:test_overview)
 
     assert_nil menu_mapper.find(:test_overview)
   end
diff --git a/spec/legacy/unit/mail_handler_spec.rb b/spec/legacy/unit/mail_handler_spec.rb
index 92b0d4b79e..f95108ded4 100644
--- a/spec/legacy/unit/mail_handler_spec.rb
+++ b/spec/legacy/unit/mail_handler_spec.rb
@@ -65,7 +65,7 @@ describe MailHandler, type: :model do
     assert !issue.description.match(/^Start Date:/i)
     # Email notification should be sent
     mail = ActionMailer::Base.deliveries.last
-    assert_not_nil mail
+    refute_nil mail
     assert mail.subject.include?('New ticket on a given project')
   end
 
diff --git a/spec/legacy/unit/project_spec.rb b/spec/legacy/unit/project_spec.rb
index f4ac99999b..db75e4e638 100644
--- a/spec/legacy/unit/project_spec.rb
+++ b/spec/legacy/unit/project_spec.rb
@@ -736,12 +736,12 @@ describe Project, type: :model do
   it 'should close completed versions' do
     Version.update_all("status = 'open'")
     project = Project.find(1)
-    assert_not_nil project.versions.detect { |v| v.completed? && v.status == 'open' }
-    assert_not_nil project.versions.detect { |v| !v.completed? && v.status == 'open' }
+    refute_nil project.versions.detect { |v| v.completed? && v.status == 'open' }
+    refute_nil project.versions.detect { |v| !v.completed? && v.status == 'open' }
     project.close_completed_versions
     project.reload
     assert_nil project.versions.detect { |v| v.completed? && v.status != 'closed' }
-    assert_not_nil project.versions.detect { |v| !v.completed? && v.status == 'open' }
+    refute_nil project.versions.detect { |v| !v.completed? && v.status == 'open' }
   end
 
   it 'should export work packages is allowed' do
@@ -800,7 +800,7 @@ describe Project, type: :model do
       assert copied_issue
       assert copied_issue.fixed_version
       assert_equal 'Assigned Issues', copied_issue.fixed_version.name # Same name
-      assert_not_equal assigned_version.id, copied_issue.fixed_version.id # Different record
+      refute_equal assigned_version.id, copied_issue.fixed_version.id # Different record
     end
 
     it 'should change the new issues to use the copied closed version' do
@@ -822,7 +822,7 @@ describe Project, type: :model do
       assert copied_issue
       assert copied_issue.fixed_version
       assert_equal 'Assigned Issues', copied_issue.fixed_version.name # Same name
-      assert_not_equal assigned_version.id, copied_issue.fixed_version.id # Different record
+      refute_equal assigned_version.id, copied_issue.fixed_version.id # Different record
     end
 
     it 'should copy issue relations' do
@@ -850,14 +850,14 @@ describe Project, type: :model do
       copied_relation = copied_issue.relations.first
       assert_equal 'relates', copied_relation.relation_type
       assert_equal copied_second_issue.id, copied_relation.to_id
-      assert_not_equal source_relation.id, copied_relation.id
+      refute_equal source_relation.id, copied_relation.id
 
       # Second issue with a cross project relation
       assert_equal 2, copied_second_issue.relations.size, 'Relation not copied'
       copied_relation = copied_second_issue.relations.find { |r| r.relation_type == 'duplicates' }
       assert_equal 'duplicates', copied_relation.relation_type
       assert_equal 1, copied_relation.from_id, 'Cross project relation not kept'
-      assert_not_equal source_relation_cross_project.id, copied_relation.id
+      refute_equal source_relation_cross_project.id, copied_relation.id
     end
 
     it 'should copy memberships' do
@@ -891,7 +891,7 @@ describe Project, type: :model do
 
       assert @project.copy(@source_project)
       member = Member.find_by(user_id: user.id, project_id: @project.id)
-      assert_not_nil member
+      refute_nil member
       assert_equal [1, 2], member.role_ids.sort
     end
 
@@ -927,7 +927,7 @@ describe Project, type: :model do
       end
 
       assert @project.wiki
-      assert_not_equal @source_project.wiki, @project.wiki
+      refute_equal @source_project.wiki, @project.wiki
       assert_equal 'Start page', @project.wiki.start_page
     end
 
@@ -978,7 +978,7 @@ describe Project, type: :model do
       @project.work_packages.each do |issue|
         assert issue.category
         assert_equal 'Stock management', issue.category.name # Same name
-        assert_not_equal Category.find(3), issue.category # Different record
+        refute_equal Category.find(3), issue.category # Different record
       end
     end
 
diff --git a/spec/legacy/unit/query_spec.rb b/spec/legacy/unit/query_spec.rb
index a9ed6e0de8..8999dc7a4a 100644
--- a/spec/legacy/unit/query_spec.rb
+++ b/spec/legacy/unit/query_spec.rb
@@ -48,7 +48,7 @@ describe Query, type: :model do
     # User.current should be anonymous here
     query = Query.new(project: nil, name: '_')
     project_filter = query.available_work_package_filters['project_id']
-    assert_not_nil project_filter
+    refute_nil project_filter
     project_ids = project_filter[:values].map { |p| p[1] }
     assert project_ids.include?('1')  # public project
     assert !project_ids.include?('2') # private project anonymous user cannot see
@@ -235,7 +235,7 @@ describe Query, type: :model do
     User.current = User.find(1)
     query = Query.new(name: '_', filters: [Queries::WorkPackages::Filter.new(:watcher_id, operator: '=', values: ['me'])])
     result = find_issues_with_query(query)
-    assert_not_nil result
+    refute_nil result
     assert !result.empty?
     assert_equal WorkPackage.visible.watched_by(User.current).sort_by(&:id), result.sort_by(&:id)
     User.current = nil
@@ -245,7 +245,7 @@ describe Query, type: :model do
     User.current = User.find(1)
     query = Query.new(name: '_', filters: [Queries::WorkPackages::Filter.new(:watcher_id, operator: '!', values: ['me'])])
     result = find_issues_with_query(query)
-    assert_not_nil result
+    refute_nil result
     assert !result.empty?
     assert_equal((WorkPackage.visible - WorkPackage.watched_by(User.current)).sort_by(&:id).size, result.sort_by(&:id).size)
     User.current = nil
@@ -272,9 +272,9 @@ describe Query, type: :model do
   it 'should grouped with valid column' do
     q = Query.new(group_by: 'status', name: '_')
     assert q.grouped?
-    assert_not_nil q.group_by_column
+    refute_nil q.group_by_column
     assert_equal :status, q.group_by_column.name
-    assert_not_nil q.group_by_statement
+    refute_nil q.group_by_statement
     assert_equal 'status', q.group_by_statement
   end
 
@@ -427,13 +427,13 @@ describe Query, type: :model do
 
     it 'should include users of visible projects in cross-project view' do
       users = @query.available_work_package_filters['assigned_to_id']
-      assert_not_nil users
+      refute_nil users
       assert users[:values].map { |u| u[1] }.include?('3')
     end
 
     it 'should include visible projects in cross-project view' do
       projects = @query.available_work_package_filters['project_id']
-      assert_not_nil projects
+      refute_nil projects
       assert projects[:values].map { |u| u[1] }.include?('1')
     end
 
diff --git a/spec/legacy/unit/repository_spec.rb b/spec/legacy/unit/repository_spec.rb
index da979020d8..d3134664b8 100644
--- a/spec/legacy/unit/repository_spec.rb
+++ b/spec/legacy/unit/repository_spec.rb
@@ -130,7 +130,7 @@ describe Repository, type: :model do
       comments: comment, commit_date: Time.now, revision: 0, scmid: 'f39b7922fb3c',
       committer: 'foo <foo@example.com>', committed_on: Time.now, repository: repository)
     assert(changeset.save)
-    assert_not_equal(comment, changeset.comments)
+    refute_equal(comment, changeset.comments)
     assert_equal('This is a looooooooooooooong comment', changeset.comments)
   end
 
diff --git a/spec/legacy/unit/repository_subversion_spec.rb b/spec/legacy/unit/repository_subversion_spec.rb
index 300b9ef617..fb6b5f84d3 100644
--- a/spec/legacy/unit/repository_subversion_spec.rb
+++ b/spec/legacy/unit/repository_subversion_spec.rb
@@ -83,7 +83,7 @@ describe Repository::Subversion, type: :model do
     @repository.reload
 
     entries = @repository.entries('subversion_test/[folder_with_brackets]')
-    assert_not_nil entries, 'Expect to find entries in folder_with_brackets'
+    refute_nil entries, 'Expect to find entries in folder_with_brackets'
     assert_equal 1, entries.size, 'Expect one entry in folder_with_brackets'
     assert_equal 'README.txt', entries.first.name
   end
@@ -102,7 +102,7 @@ describe Repository::Subversion, type: :model do
     assert_equal 2, @repository.file_changes.count, 'Expected to see 2 changes, dir add and file add'
 
     entries = @repository.entries('')
-    assert_not_nil entries, 'Expect to find entries'
+    refute_nil entries, 'Expect to find entries'
     assert_equal 1, entries.size, 'Expect a single entry'
     assert_equal 'README.txt', entries.first.name
   end
diff --git a/spec/legacy/unit/token_spec.rb b/spec/legacy/unit/token_spec.rb
index 0af172b96a..ec224f2bf9 100644
--- a/spec/legacy/unit/token_spec.rb
+++ b/spec/legacy/unit/token_spec.rb
@@ -42,7 +42,7 @@ describe Token do
     user = User.find(1)
     t1 = Token.create(user: user, action: 'autologin')
     t2 = Token.create(user: user, action: 'autologin')
-    assert_not_equal t1.value, t2.value
+    refute_equal t1.value, t2.value
     assert !Token.exists?(t1.id)
     assert Token.exists?(t2.id)
   end
diff --git a/spec/legacy/unit/user_spec.rb b/spec/legacy/unit/user_spec.rb
index 181565a50d..fecbe8e53e 100644
--- a/spec/legacy/unit/user_spec.rb
+++ b/spec/legacy/unit/user_spec.rb
@@ -400,7 +400,7 @@ describe User, type: :model do
 
   it 'should find by mail should be case insensitive' do
     u = User.find_by_mail('JSmith@somenet.foo')
-    assert_not_nil u
+    refute_nil u
     assert_equal 'jsmith@somenet.foo', u.mail
   end
 
diff --git a/spec/legacy/unit/wiki_page_spec.rb b/spec/legacy/unit/wiki_page_spec.rb
index a57e11b7ed..9badbce904 100644
--- a/spec/legacy/unit/wiki_page_spec.rb
+++ b/spec/legacy/unit/wiki_page_spec.rb
@@ -140,7 +140,7 @@ describe WikiPage, type: :model do
   it 'should updated on eager load' do
     page = WikiPage.with_updated_on.first
     assert page.is_a?(WikiPage)
-    assert_not_nil page.read_attribute(:updated_on)
+    refute_nil page.read_attribute(:updated_on)
     assert_equal page.content.updated_on, page.updated_on
   end
 end