diff --git a/Gemfile b/Gemfile
index 7652b503..71acfe10 100644
--- a/Gemfile
+++ b/Gemfile
@@ -22,7 +22,6 @@ gem "pundit", "~> 1.1.0"
 gem "recaptcha", require: "recaptcha/rails"
 gem "loofah", "<= 2.20.0"
 gem "whenever", require: false # for cron jobs
-gem "squeel" # , '~> 1.1.1' # until version 1.1.2 released
 gem "tilt"
 gem "simple-navigation", "3.11.0"
 gem "simple_form", "3.2.1"
diff --git a/Gemfile.lock b/Gemfile.lock
index a013d206..0d739b05 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -223,8 +223,6 @@ GEM
     pdfkit (0.8.2)
     pg (0.21.0)
     pkg-config (1.5.1)
-    polyamorous (1.1.0)
-      activerecord (>= 3.0)
     prawn (2.2.2)
       pdf-core (~> 0.7.0)
       ttfunk (~> 1.5)
@@ -363,10 +361,6 @@ GEM
       actionpack (>= 3.0)
       activesupport (>= 3.0)
       sprockets (>= 2.8, < 4.0)
-    squeel (1.2.3)
-      activerecord (>= 3.0)
-      activesupport (>= 3.0)
-      polyamorous (~> 1.1.0)
     ssrf_filter (1.0.8)
     standard (1.0.5)
       rubocop (= 1.12.1)
@@ -468,7 +462,6 @@ DEPENDENCIES
   simplecov
   sinatra
   spring
-  squeel
   standard
   strong_presenter (~> 0.2.2)
   superfish-rails (~> 1.6.0)
diff --git a/app/controllers/contests_controller.rb b/app/controllers/contests_controller.rb
index 864b0bd0..172e35cf 100644
--- a/app/controllers/contests_controller.rb
+++ b/app/controllers/contests_controller.rb
@@ -24,13 +24,24 @@ def browse
     case params[:filter].to_s
     when "active"
       raise Pundit::NotAuthorizedError unless user_signed_in?
-      @contests = Contest.joins(:contest_relations).where { (contest_relations.user_id == my { current_user.id }) & (contest_relations.finish_at > Time.now) }.order("end_time ASC")
+      @contests = Contest
+        .joins(:contest_relations)
+        .where(contest_relations: { user_id: current_user.id })
+        .where("contest_relations.finish_at > ?", Time.now)
+        .order("end_time ASC")
     when "current"
-      @contests = visible_contests.where { (start_time < Time.now + 30.minutes) & (end_time > Time.now) }.order("end_time ASC")
+      @contests = visible_contests
+        .where("start_time < ?", Time.now + 30.minutes)
+        .where("end_time > ?", Time.now)
+        .order("end_time ASC")
     when "upcoming"
-      @contests = visible_contests.where { (start_time > Time.now + 30.minutes) }.order("start_time ASC")
+      @contests = visible_contests
+        .where("start_time > ?", Time.now + 30.minutes)
+        .order("start_time ASC")
     when "past"
-      @contests = visible_contests.where { (end_time < Time.now) }.order("end_time DESC")
+      @contests = visible_contests
+        .where("end_time < ?", Time.now)
+        .order("end_time DESC")
     else
       raise Pundit::NotAuthorizedError
     end
diff --git a/app/controllers/groups/members_controller.rb b/app/controllers/groups/members_controller.rb
index 7e42bba6..a421ddeb 100644
--- a/app/controllers/groups/members_controller.rb
+++ b/app/controllers/groups/members_controller.rb
@@ -97,8 +97,8 @@ def invites
         redirect_to(invites_members_group_path(@group), notice: "#{@user.username} has been invited to join this group")
       end
     else # get request
-      @pending_requests = @group.invitations.pending.order(:created_at).reverse_order
-      @requests = @group.invitations.closed.order(:created_at).reverse_order
+      @pending_requests = @group.invitations.merge(Request.pending).order(created_at: :desc)
+      @requests = @group.invitations.merge(Request.closed).order(created_at: :desc)
     end
   end
 
diff --git a/app/controllers/home_controller.rb b/app/controllers/home_controller.rb
index b7942003..763c32b7 100644
--- a/app/controllers/home_controller.rb
+++ b/app/controllers/home_controller.rb
@@ -2,6 +2,6 @@ class HomeController < ApplicationController
   def home
     @mygroups = current_user.try(:groups)
     @problem_set_associations = Group.find(0).problem_set_associations
-    @contests = policy_scope(Contest).where { (end_time > Time.now) }.order("end_time ASC")
+    @contests = policy_scope(Contest).not_ended.order("end_time ASC")
   end
 end
diff --git a/app/controllers/problems_controller.rb b/app/controllers/problems_controller.rb
index 3db6593f..a830a994 100644
--- a/app/controllers/problems_controller.rb
+++ b/app/controllers/problems_controller.rb
@@ -91,7 +91,13 @@ def submissions
     if current_user.openbook?
       @submissions = @problem.submission_history(current_user)
     else
-      start_time = current_user.contest_relations.joins(contest: {problem_set: :problems}).where { (started_at <= DateTime.now) & (finish_at > DateTime.now) & (contest.problem_set.problems.id == my { params[:id] }) }.minimum(:started_at)
+      start_time = current_user
+        .contest_relations
+        .joins(contest: {problem_set: :problems})
+        .where("started_at <= :now AND finish_at > :now", now: DateTime.now)
+        .where(problems: {id: params[:id]})
+        .minimum(:started_at)
+
       @submissions = @problem.submission_history(current_user, start_time)
     end
 
diff --git a/app/controllers/user_controller.rb b/app/controllers/user_controller.rb
index a5d58d44..e6dd4588 100644
--- a/app/controllers/user_controller.rb
+++ b/app/controllers/user_controller.rb
@@ -9,7 +9,12 @@ def permitted_params
   def show
     @user = User.find(params[:id])
     authorize @user, :show?
-    @solved_problems = @user.user_problem_relations.where(ranked_score: 100).joins(:problem).select([:problem_id, :ranked_submission_id, {problem: :name}]).order("problems.name")
+    @solved_problems = @user
+      .user_problem_relations
+      .where(ranked_score: 100)
+      .joins(:problem)
+      .select("problems.name", "problem_id", "ranked_submission_id")
+      .order("problems.name")
   end
 
   def edit
diff --git a/app/models/contest.rb b/app/models/contest.rb
index fce12562..61fba1be 100644
--- a/app/models/contest.rb
+++ b/app/models/contest.rb
@@ -24,6 +24,9 @@ class Contest < ActiveRecord::Base
   # public = everyone, protected = in group, private = competitors
   OBSERVATION = Enumeration.new 0 => :public, 1 => :protected, 2 => :private
 
+  scope :not_ended, -> { where("end_time > ?", Time.current) }
+  scope :publicly_observable, -> { where(observation: OBSERVATION[:public]) }
+
   before_save do # update the end time that was cached
     if duration_changed? || end_time_changed?
       contest_relations.find_each do |relation|
diff --git a/app/models/contest_relation.rb b/app/models/contest_relation.rb
index 842ce85a..5ad74803 100644
--- a/app/models/contest_relation.rb
+++ b/app/models/contest_relation.rb
@@ -7,7 +7,7 @@ class ContestRelation < ActiveRecord::Base
   belongs_to :school
   belongs_to :supervisor, class_name: :User
 
-  scope :active, -> { where { (started_at <= DateTime.now) & (finish_at > DateTime.now) } }
+  scope :active, -> { where("started_at <= :now AND finish_at > :now", now: DateTime.now) }
   scope :absent, -> { where(checked_in: false) }
   scope :user, ->(u_id) { where(user_id: u_id) }
 
diff --git a/app/models/contest_supervisor.rb b/app/models/contest_supervisor.rb
index 771e02df..97849c35 100644
--- a/app/models/contest_supervisor.rb
+++ b/app/models/contest_supervisor.rb
@@ -36,7 +36,10 @@ def contest_relations
 
   def potential_contestants
     if site_type == "School"
-      User.where { |user| (user.school_id == site_id) & ((user.school_graduation >= contest.end_time) | ((user.school_graduation.nil?) & (user.created_at >= DateTime.now.advance(years: -1)))) & (user.id << contest.registrants) }
+      User
+        .where(school_id: site_id)
+        .where("(users.school_graduation >= :contest_end_time) OR ((users.school_graduation IS NULL) AND (users.created_at >= :year_ago))", contest_end_time: contest.end_time, year_ago: DateTime.now.advance(years: -1))
+        .where.not(id: contest.registrants)
     else
       [] # not implemented
     end
diff --git a/app/models/problem_set.rb b/app/models/problem_set.rb
index 1baea68f..20f20b75 100644
--- a/app/models/problem_set.rb
+++ b/app/models/problem_set.rb
@@ -17,11 +17,19 @@ class ProblemSet < ActiveRecord::Base
   validates :name, presence: true
 
   def problems_with_scores_by_user(user_id)
-    problems.joins("LEFT OUTER JOIN user_problem_relations ON user_problem_relations.problem_id = problems.id AND user_problem_relations.user_id = #{user_id} LEFT OUTER JOIN submissions ON submissions.id = user_problem_relations.submission_id").select([:id, :name, :test_error_count, :test_warning_count, :test_status, {submissions: [:points, :maximum_points], problem_set_problems: :weighting}])
+    problems
+      .joins("LEFT OUTER JOIN user_problem_relations ON user_problem_relations.problem_id = problems.id AND user_problem_relations.user_id = #{user_id} LEFT OUTER JOIN submissions ON submissions.id = user_problem_relations.submission_id")
+      .select(
+        "id", "name", "test_error_count", "test_warning_count", "test_status", "submissions.points", "submissions.maximum_points", "problem_set_problems.weighting"
+      )
   end
 
-  def for_contestant? u_id
-    contests.joins(:contest_relations).where(contest_relations: {user_id: u_id}).where { {contest_relations => sift(:active)} }.any?
+  def for_contestant?(u_id)
+    contests
+      .joins(:contest_relations)
+      .where(contest_relations: {user_id: u_id})
+      .merge(ContestRelation.active)
+      .any?
   end
 
   def for_owner? u_id
diff --git a/app/models/request.rb b/app/models/request.rb
index 2126c1b2..63fde6e8 100644
--- a/app/models/request.rb
+++ b/app/models/request.rb
@@ -16,9 +16,23 @@ class Request < ActiveRecord::Base
       status == key
     end
   end
-  scope :pending, -> { where { (status == STATUS[:pending]) & (expired_at > DateTime.now) } }
-  scope :expired, -> { where { (status == STATUS[:pending]) & (expired_at <= DateTime.now) } }
-  scope :closed, -> { where { (status != STATUS[:pending]) | (expired_at <= DateTime.now) } }
+
+  # I would prefer to just use expired and not_expired, but these
+  # names are in used below for a slightly different use.
+  scope :past_expiry, -> { where("expired_at <= ?", DateTime.now) }
+  scope :not_past_expiry, -> { where("expired_at > ?", DateTime.now) }
+
+  # IMO a better name for this would be "pending", but see below
+  scope :status_pending, -> { where(status: STATUS[:pending]) }
+
+  # These scopes have weird names.
+  # * Pending is redefined a scope defined above.
+  # * Expired you wouldn't usually expect to check status
+  scope :pending, -> { status_pending.merge(not_past_expiry) }
+  scope :expired, -> { status_pending.merge(past_expiry) }
+
+  # TODO(Rails5): Convert to where.not(pending).or(past_expiry)
+  scope :closed, -> { where("status != ? OR expired_at <= ?", STATUS[:pending], DateTime.now) }
 
   def pending?
     status == STATUS[:pending] && (expired_at == Float::INFINITY || expired_at > DateTime.now)
diff --git a/app/policies/contest_policy.rb b/app/policies/contest_policy.rb
index 1c0b5f22..5c0f85bc 100644
--- a/app/policies/contest_policy.rb
+++ b/app/policies/contest_policy.rb
@@ -5,25 +5,30 @@ def resolve
         return scope.all
       end
 
-      # following uses advanced squeel
-      scope.where do |contests|
-        public_observation = contests.observation == Contest::OBSERVATION[:public]
-        grouped = contests.id.in(GroupContest.where do |gc|
-          group_contests = (gc.group_id == 0)
-          group_contests |= (gc.group_id >> user.groups.select(:id)) if user
-          group_contests
-        end.select(:contest_id))
-        visible_contests = public_observation | grouped
-
-        if user
-          registered = contests.id.in(user.contest_relations.select(:contest_id))
-          owned = contests.owner_id == user.id
-          supervising = contests.id.in(user.contest_supervising.select(:contest_id))
-          visible_contests |= registered | owned | supervising
-        end
-
-        visible_contests
-      end
+      sql = <<~SQL
+        contests.observation = :public
+        OR contests.id IN (
+          SELECT
+            contest_id
+          FROM
+            group_contests
+          WHERE
+            group_id = 0
+            OR group_id IN (:user_groups)
+        )
+        OR contests.id IN (:allowed_contest_ids)
+        OR contests.owner_id = :user_id
+      SQL
+
+      allowed_contest_ids = []
+      allowed_contest_ids = user.contest_relations.pluck(:contest_id) + user.contest_supervising.pluck(:contest_id) if user
+
+      scope.where(sql, {
+        public: Contest::OBSERVATION[:public],
+        user_groups: user&.groups&.pluck(:id),
+        allowed_contest_ids: allowed_contest_ids,
+        user_id: user&.id,
+      })
     end
   end
 
@@ -34,12 +39,22 @@ def registered?
 
   def current_contestant?
     return false unless user # signed in
-    record.contest_relations.where { |relation| (relation.user_id == user.id) & (relation.started_at <= DateTime.now) & (relation.finish_at > DateTime.now) }.exists?
+
+    record
+      .contest_relations
+      .where(user_id: user.id)
+      .where("started_at <= :now AND finish_at > :now", DateTime.now)
+      .exists?
   end
 
   def current_or_past_contestant?
     return false unless user # signed in
-    record.contest_relations.where { |relation| (relation.user_id == user.id) & (relation.started_at <= DateTime.now) }.exists?
+
+    record
+      .contest_relations
+      .where(user_id: user.id)
+      .where("started_at <= ?", DateTime.now)
+      .exists?
   end
 
   def index?
@@ -87,7 +102,7 @@ def unfinalize?
 
   def startable?
     return false unless user # signed in
-    user.is_staff? or registered? or record.groups.where(id: 0).exists? or record.groups.joins(:memberships).where(memberships: {member_id: user.id}).exists?
+    user.is_staff? || registered? || record.groups.where(id: 0).exists? || record.groups.joins(:memberships).where(group_memberships: { member_id: user.id }).exists?
   end
 
   def start?
diff --git a/app/policies/group_policy.rb b/app/policies/group_policy.rb
index 234d161d..d34a1aa2 100644
--- a/app/policies/group_policy.rb
+++ b/app/policies/group_policy.rb
@@ -4,7 +4,11 @@ def resolve(source = nil)
       if user.is_staff?
         scope.all
       else
-        scope.where { |groups| (groups.id == 0) | (groups.visibility == Group::VISIBILITY[:public]) | (groups.owner_id == user.id) }
+        scope.where(
+          "id = 0 OR visibility = :public OR owner_id = :user_id",
+          public: Group::VISIBILITY[:public],
+          user_id: user.id
+        )
       end
     end
   end
diff --git a/app/policies/problem_policy.rb b/app/policies/problem_policy.rb
index 08267d77..c51ca2bf 100644
--- a/app/policies/problem_policy.rb
+++ b/app/policies/problem_policy.rb
@@ -32,12 +32,21 @@ def show?
     return true if user && user.is_staff?
 
     if user && user.competing?
-      return record.contest_relations.where { |relation| (relation.user_id == user.id) & (relation.started_at <= DateTime.now) & (relation.finish_at > DateTime.now) }.exists?
+      return record
+        .contest_relations
+        .where(contest_relations: { user_id: user.id })
+        .where("started_at <= :now AND finish_at > :now", now: DateTime.now)
+        .exists?
     end
 
     return true if record.groups.where(id: 0).exists?
     return false unless user # signed in
-    user.owns(record) or record.group_memberships.where { |membership| (membership.member_id == user.id) }.exists?
+    return true if user.owns(record)
+
+    record
+      .group_memberships
+      .where(group_memberships: { member_id: user.id })
+      .exists?
   end
 
   def access?
diff --git a/app/policies/problem_set_policy.rb b/app/policies/problem_set_policy.rb
index ab39a2c8..5a9d4893 100644
--- a/app/policies/problem_set_policy.rb
+++ b/app/policies/problem_set_policy.rb
@@ -24,16 +24,20 @@ def manage?
   def show?
     return true if user && user.is_staff?
     if user && user.competing?
-      return user.contest_relations.where { |relation| (relation.started_at <= DateTime.now) & (relation.finish_at > DateTime.now) & (relation.contest_id >> record.contest_ids) }.exists?
+      return user
+        .contest_relations
+        .where("started_at <= :now AND finish_at > :now", now: DateTime.now)
+        .where("contest_relations.contest_id IN (:contest_ids)", contest_ids: record.contest_ids)
+        .exists?
     end
 
     return true if record.groups.where(id: 0).exists?
     return false unless user # signed in
-    user.owns(record) or record.group_memberships.where { |membership| (membership.member_id == user.id) }.exists?
+    user.owns(record) || record.group_memberships.where(member_id: user.id).exists?
   end
 
   def create?
     return false unless user # signed in
-    super or user.is_staff? or user.is_any?([:organiser, :author])
+    super || user.is_staff? || user.is_any?([:organiser, :author])
   end
 end
diff --git a/app/policies/request_policy.rb b/app/policies/request_policy.rb
index 641e86cb..8c073fe9 100644
--- a/app/policies/request_policy.rb
+++ b/app/policies/request_policy.rb
@@ -4,7 +4,7 @@ def resolve
       if user.is_admin?
         scope.all
       else
-        scope.where { (requester_id == user.id) | (requestee_id == user.id) }
+        scope.where("requester_id = :user_id OR requestee_id = :user_id", user_id: user.id)
       end
     end
   end
diff --git a/app/policies/submission_policy.rb b/app/policies/submission_policy.rb
index ce12dd79..e7d51e74 100644
--- a/app/policies/submission_policy.rb
+++ b/app/policies/submission_policy.rb
@@ -4,20 +4,31 @@ def resolve
       if user.is_staff?
         scope.all
       elsif user.competing?
-        problem_set_ids = ContestRelation.where { |contest_relations| (contest_relations.user_id == user.id) & (contest_relations.started_at <= DateTime.now) & (contest_relations.finish_at > DateTime.now) }.joins(:contest).select(contest: :problem_set_id)
-        scope.joins(problem: :problem_sets).where(problem: {problem_sets: {id: problem_set_ids}}, user_id: user.id)
+        problem_set_ids = ContestRelation
+          .where(user_id: user.id)
+          .where("contest_relations.started_at <= ?", DateTime.now)
+          .where("contest_relations.finish_at > ?", DateTime.now)
+          .joins(:contest)
+          .select("contests.problem_set_id")
+
+        scope
+          .joins(problem: :problem_sets)
+          .where(user_id: user.id)
+          .where(problem_sets: {id: problem_set_ids})
       else
-        scope.joins(:problem).where { |submission| (submission.user_id == user.id) | (submission.problem.owner_id == user.id) }
+        scope
+          .joins(:problem)
+          .where("submissions.user_id = :user_id OR problems.owner_id = :user_id", user_id: user.id)
       end
     end
   end
 
   def inspect?
-    super or (record.is_a?(Submission) && policy(record.problem).try(:inspect?) && !user.competing?)
+    super || (record.is_a?(Submission) && policy(record.problem).try(:inspect?) && !user.competing?)
   end
 
   def update?
-    super or (record.is_a?(Submission) && policy(record.problem).try(:update?) && !user.competing?)
+    super || (record.is_a?(Submission) && policy(record.problem).try(:update?) && !user.competing?)
   end
 
   def index?
@@ -25,7 +36,7 @@ def index?
   end
 
   def show?
-    inspect? or scope.where(id: record.id).exists?
+    inspect? || scope.where(id: record.id).exists?
   end
 
   def rejudge?
diff --git a/app/workers/judge_submission_worker.rb b/app/workers/judge_submission_worker.rb
index 658881c2..a759846f 100644
--- a/app/workers/judge_submission_worker.rb
+++ b/app/workers/judge_submission_worker.rb
@@ -13,10 +13,16 @@ def self.judge(submission, queue: nil, delay: 0)
     user = submission.user
     if user.competing? && Pundit.policy(user, submission).show?
       if rejudging # re-judging, later submissions are more important
-        later = Submission.where(problem_id: submission.problem_id, user_id: submission.user_id).where { created_at > submission.created_at }.count
+        later = Submission
+          .where(problem_id: submission.problem_id, user_id: submission.user_id)
+          .where("created_at > ?", submission.created_at)
+          .count
         priority = 18 - [later * 2, 10].min
       else # first time judging, earlier submissions get better priority (so other people get a chance to have their stuff judged)
-        prev = Submission.where(problem_id: submission.problem_id, user_id: submission.user_id).where { created_at < submission.created_at }.count
+        prev = Submission
+          .where(problem_id: submission.problem_id, user_id: submission.user_id)
+          .where("created_at < ?", submission.created_at)
+          .count
 
         priority = 20 - [prev, 10].min
       end
@@ -102,7 +108,7 @@ def judge
       resource_limits = {mem: memory_limit * 1024, time: time_limit, extra_time: extra_time, wall_time: wall_time, stack: stack_limit, processes: submission.language.processes}
 
       # prerequisites
-      prereqs = problem.test_cases.where(id: problem.prerequisite_sets.joins(:test_case_relations).select(test_case_relations: :test_case_id))
+      prereqs = problem.test_cases.where(id: problem.prerequisite_sets.joins(:test_case_relations).select("test_case_relations.test_case_id"))
 
       prereqs.each do |test_case|
         result["test_cases"][test_case.id] = judge_test_case(test_case, run_command, eval_command, resource_limits) unless result["test_cases"].has_key?(test_case.id)
diff --git a/db/migrate/20131221014009_create_user_problem_relation.rb b/db/migrate/20131221014009_create_user_problem_relation.rb
index 8098d012..2a426baf 100644
--- a/db/migrate/20131221014009_create_user_problem_relation.rb
+++ b/db/migrate/20131221014009_create_user_problem_relation.rb
@@ -2,7 +2,7 @@ class CreateUserProblemRelation < ActiveRecord::Migration
   def change
     reversible do |dir|
       dir.up do
-        missing_user_ids = Submission.where { |submission| submission.user_id << User.select(:id) }.pluck(:user_id)
+        missing_user_ids = Submission.where("submissions.user_id NOT IN (SELECT id FROM users)").pluck(:user_id)
 
         Submission.where(user_id: missing_user_ids).delete_all
         ContestRelation.where(user_id: missing_user_ids).destroy_all
diff --git a/spec/factories/contest_supervisors.rb b/spec/factories/contest_supervisors.rb
index 5eb068db..5f6cf9df 100644
--- a/spec/factories/contest_supervisors.rb
+++ b/spec/factories/contest_supervisors.rb
@@ -1,10 +1,9 @@
 # Read about factories at https://github.com/thoughtbot/factory_bot
 
 FactoryBot.define do
-  factory :contest_supervisor, class: "ContestSupervisors" do
-    contest_id { 1 }
-    user_id { 1 }
-    site_type { "MyString" }
-    site_id { 1 }
+  factory :contest_supervisor, class: "ContestSupervisor" do
+    association :contest
+    association :user
+    association :site, factory: :school
   end
 end
diff --git a/spec/models/contest_supervisor_spec.rb b/spec/models/contest_supervisor_spec.rb
index 2a510328..512d4870 100644
--- a/spec/models/contest_supervisor_spec.rb
+++ b/spec/models/contest_supervisor_spec.rb
@@ -1,5 +1,45 @@
 require "spec_helper"
 
 describe ContestSupervisor do
-  pending "add some examples to (or delete) #{__FILE__}"
+  subject(:contest_supervisor) { FactoryBot.create(:contest_supervisor, contest: contest) }
+
+  let(:contest) { FactoryBot.create(:contest) }
+
+  describe "#potential_contestants" do
+    let!(:students) do
+      10.times.map {
+        FactoryBot.create(:user, country_code: "NZ", school: contest_supervisor.site)
+      }
+    end
+
+    context "when no-one is registered for the contest" do
+      it "includes all the students at the school" do
+        expect(contest_supervisor.potential_contestants).to match_array(students)
+      end
+    end
+
+    context "when some people are registered for the contest" do
+      before do
+        students.take(5).each do |student|
+          contest.registrants << student
+        end
+      end
+
+      it "includes the remaining students at the school" do
+        expect(contest_supervisor.potential_contestants).to match_array(students.drop(5))
+      end
+    end
+
+    context "when no-one is registered for the contest" do
+      before do
+        students.each do |student|
+          contest.registrants << student
+        end
+      end
+
+      it "return an empty list" do
+        expect(contest_supervisor.potential_contestants).to be_empty
+      end
+    end
+  end
 end
diff --git a/spec/requests/submissions_request_spec.rb b/spec/requests/submissions_request_spec.rb
new file mode 100644
index 00000000..c4f5388c
--- /dev/null
+++ b/spec/requests/submissions_request_spec.rb
@@ -0,0 +1,44 @@
+require "spec_helper"
+
+RSpec.describe SubmissionsController, type: :request do
+  let(:problem) { FactoryBot.create(:problem) }
+  let(:problem_set) { FactoryBot.create(:problem_set, problems: [problem]) }
+  let(:user) { FactoryBot.create(:user, groups: [group]) }
+  let(:group) { FactoryBot.create(:group) }
+  let!(:submission) { FactoryBot.create(:submission, problem: problem, user: user) }
+
+  before do
+    problem_set.groups << group
+
+    sign_in(user)
+  end
+
+  describe "GET /problems/:id/submissions" do
+    it "doesn't explode" do
+      get submissions_problem_path(problem)
+
+      expect(response).to have_http_status(:success)
+    end
+  end
+
+  describe "GET /submissions/my" do
+    context "when not in an active contest" do
+      it "doesn't explode" do
+        get my_submissions_path
+
+        expect(response).to have_http_status(:success)
+      end
+    end
+
+    context "when in an active contest" do
+      let(:contest) { FactoryBot.create(:contest, problem_set: problem_set) }
+      let!(:contest_relation) { FactoryBot.create(:contest_relation, user: user, contest: contest, finish_at: 99.years.from_now) }
+
+      it "doesn't explode" do
+        get my_submissions_path
+
+        expect(response).to have_http_status(:success)
+      end
+    end
+  end
+end