Reduce number of requests in user tests

We were adding a `visit` in a `before` block but then we started some
tests with another `visit`.

We also destroyed records in the database in between, which increased
the risk of database inconsistency since the process running the browser
had already been started.

Besides, some tests were wrong; they were visiting a page with the
browser, then destroying records in the database, and then checking the
page without reloading the browser. Since we aren't automatically
refreshing the affected areas of the page, obviously the page content
before and after destroying records is exactly the same, and the test
was passing because it's testing content that isn't there in any
situation.

spec/system/users_spec.rb

@@ -4,16 +4,14 @@ describe "Users" do
   describe "Show (public page)" do
     let(:user) { create(:user) }
 
-    before do
-      1.times { create(:debate, author: user) }
-      2.times { create(:proposal, author: user) }
-      3.times { create(:budget_investment, author: user) }
-      4.times { create(:comment, user: user) }
-
-      visit user_path(user)
-    end
+    let!(:debates)     { 1.times.map { create(:debate, author: user) } }
+    let!(:proposals)   { 2.times.map { create(:proposal, author: user) } }
+    let!(:investments) { 3.times.map { create(:budget_investment, author: user) } }
+    let!(:comments)    { 4.times.map { create(:comment, user: user) } }
 
     scenario "shows user public activity" do
+      visit user_path(user)
+
       expect(page).to have_content("1 Debate")
       expect(page).to have_content("2 Proposals")
       expect(page).to have_content("3 Investments")
@@ -21,7 +19,9 @@ describe "Users" do
     end
 
     scenario "shows only items where user has activity" do
-      user.proposals.destroy_all
+      proposals.each(&:destroy)
+
+      visit user_path(user)
 
       expect(page).not_to have_content("0 Proposals")
       expect(page).to have_content("1 Debate")
@@ -30,85 +30,92 @@ describe "Users" do
     end
 
     scenario "default filter is proposals" do
-      user.proposals.each do |proposal|
+      visit user_path(user)
+
+      proposals.each do |proposal|
         expect(page).to have_content(proposal.title)
       end
 
-      user.debates.each do |debate|
+      debates.each do |debate|
         expect(page).not_to have_content(debate.title)
       end
 
-      user.comments.each do |comment|
+      comments.each do |comment|
         expect(page).not_to have_content(comment.body)
       end
     end
 
     scenario "shows debates by default if user has no proposals" do
-      user.proposals.destroy_all
+      proposals.each(&:destroy)
+
       visit user_path(user)
 
-      expect(page).to have_content(user.debates.first.title)
+      expect(page).to have_content(debates.first.title)
     end
 
     scenario "shows investments by default if user has no proposals nor debates" do
-      user.proposals.destroy_all
-      user.debates.destroy_all
+      proposals.each(&:destroy)
+      debates.each(&:destroy)
+
       visit user_path(user)
 
-      expect(page).to have_content(user.budget_investments.first.title)
+      expect(page).to have_content(investments.first.title)
     end
 
     scenario "shows comments by default if user has no proposals nor debates nor investments" do
-      user.proposals.destroy_all
-      user.debates.destroy_all
-      user.budget_investments.destroy_all
+      proposals.each(&:destroy)
+      debates.each(&:destroy)
+      investments.each(&:destroy)
+
       visit user_path(user)
 
-      user.comments.each do |comment|
+      comments.each do |comment|
         expect(page).to have_content(comment.body)
       end
     end
 
     scenario "filters" do
+      visit user_path(user)
+
       click_link "1 Debate"
 
-      user.debates.each do |debate|
+      debates.each do |debate|
         expect(page).to have_content(debate.title)
       end
 
-      user.proposals.each do |proposal|
+      proposals.each do |proposal|
         expect(page).not_to have_content(proposal.title)
       end
 
-      user.comments.each do |comment|
+      comments.each do |comment|
         expect(page).not_to have_content(comment.body)
       end
 
       click_link "4 Comments"
 
-      user.comments.each do |comment|
+      comments.each do |comment|
         expect(page).to have_content(comment.body)
       end
 
-      user.proposals.each do |proposal|
+      proposals.each do |proposal|
         expect(page).not_to have_content(proposal.title)
       end
 
-      user.debates.each do |debate|
+      debates.each do |debate|
         expect(page).not_to have_content(debate.title)
       end
 
       click_link "2 Proposals"
 
-      user.proposals.each do |proposal|
+      proposals.each do |proposal|
         expect(page).to have_content(proposal.title)
       end
 
-      user.comments.each do |comment|
+      comments.each do |comment|
         expect(page).not_to have_content(comment.body)
       end
 
-      user.debates.each do |debate|
+      debates.each do |debate|
         expect(page).not_to have_content(debate.title)
       end
     end