Added tests for commits API with an unauthenticated user and a public/private project

Added test to API commits in order to handle cases for authenticated/unauthenticated user in a
private and public project.

changelogs/unreleased/34049-public-commits-should-not-require-authentication.yml

+---
+title: Added tests for commits API unauthenticated user and public/private project
+merge_request: 13287
+author: Jacopo Beschi @jacopo-beschi

spec/requests/api/commits_spec.rb

@@ -16,11 +16,13 @@ describe API::Commits do
   end
 
   describe 'GET /projects/:id/repository/commits' do
-    context 'authorized user' do
+    let(:route) { "/projects/#{project_id}/repository/commits" }
+
+    shared_examples_for 'project commits' do
       it "returns project commits" do
         commit = project.repository.commit
 
-        get api("/projects/#{project_id}/repository/commits", user)
+        get api(route, current_user)
 
         expect(response).to have_http_status(200)
         expect(response).to match_response_schema('public_api/v4/commits')
@@ -32,7 +34,7 @@ describe API::Commits do
       it 'include correct pagination headers' do
         commit_count = project.repository.count_commits(ref: 'master').to_s
 
-        get api("/projects/#{project_id}/repository/commits", user)
+        get api(route, current_user)
 
         expect(response).to include_pagination_headers
         expect(response.headers['X-Total']).to eq(commit_count)
@@ -40,14 +42,24 @@ describe API::Commits do
       end
     end
 
-    context "unauthorized user" do
-      it "does not return project commits" do
-        get api("/projects/#{project_id}/repository/commits")
+    context 'when unauthenticated', 'and project is public' do
+      let(:project) { create(:project, :public, :repository) }
+
+      it_behaves_like 'project commits'
+    end
 
-        expect(response).to have_http_status(404)
+    context 'when unauthenticated', 'and project is private' do
+      it_behaves_like '404 response' do
+        let(:request) { get api(route) }
+        let(:message) { '404 Project Not Found' }
       end
     end
 
+    context 'when authenticated', 'as a master' do
+      let(:current_user) { user }
+
+      it_behaves_like 'project commits'
+
       context "since optional parameter" do
         it "returns project commits since provided parameter" do
           commits = project.repository.commits("master")
@@ -178,6 +190,7 @@ describe API::Commits do
         end
       end
     end
+  end
 
   describe "POST /projects/:id/repository/commits" do
     let!(:url) { "/projects/#{project_id}/repository/commits" }