Rewrite the GitHub importer from scratch

Prior to this MR there were two GitHub related importers:

* Github::Import: the main importer used for GitHub projects
* Gitlab::GithubImport: importer that's somewhat confusingly used for
  importing Gitea projects (apparently they have a compatible API)

This MR renames the Gitea importer to Gitlab::LegacyGithubImport and
introduces a new GitHub importer in the Gitlab::GithubImport namespace.
This new GitHub importer uses Sidekiq for importing multiple resources
in parallel, though it also has the ability to import data sequentially
should this be necessary.

The new code is spread across the following directories:

* lib/gitlab/github_import: this directory contains most of the importer
  code such as the classes used for importing resources.
* app/workers/gitlab/github_import: this directory contains the Sidekiq
  workers, most of which simply use the code from the directory above.
* app/workers/concerns/gitlab/github_import: this directory provides a
  few modules that are included in every GitHub importer worker.

== Stages

The import work is divided into separate stages, with each stage
importing a specific set of data. Stages will schedule the work that
needs to be performed, followed by scheduling a job for the
"AdvanceStageWorker" worker. This worker will periodically check if all
work is completed and schedule the next stage if this is the case. If
work is not yet completed this worker will reschedule itself.

Using this approach we don't have to block threads by calling `sleep()`,
as doing so for large projects could block the thread from doing any
work for many hours.

== Retrying Work

Workers will reschedule themselves whenever necessary. For example,
hitting the GitHub API's rate limit will result in jobs rescheduling
themselves. These jobs are not processed until the rate limit has been
reset.

== User Lookups

Part of the importing process involves looking up user details in the
GitHub API so we can map them to GitLab users. The old importer used
an in-memory cache, but this obviously doesn't work when the work is
spread across different threads.

The new importer uses a Redis cache and makes sure we only perform
API/database calls if absolutely necessary.  Frequently used keys are
refreshed, and lookup misses are also cached; removing the need for
performing API/database calls if we know we don't have the data we're
looking for.

== Performance & Models

The new importer in various places uses raw INSERT statements (as
generated by `Gitlab::Database.bulk_insert`) instead of using Rails
models. This allows us to bypass any validations and callbacks,
drastically reducing the number of SQL queries and Gitaly RPC calls
necessary to import projects.

To ensure the code produces valid data the corresponding tests check if
the produced rows are valid according to the model validation rules.

13 files changed, 1461 insertions, 0 deletions

diff --git a/spec/lib/gitlab/legacy_github_import/branch_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/branch_formatter_spec.rb
new file mode 100644
index 00000000000..48655851140
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/branch_formatter_spec.rb
@@ -0,0 +1,70 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::BranchFormatter do
+  let(:project) { create(:project, :repository) }
+  let(:commit) { create(:commit, project: project) }
+  let(:repo) { double }
+  let(:raw) do
+    {
+      ref: 'branch-merged',
+      repo: repo,
+      sha: commit.id
+    }
+  end
+
+  describe '#exists?' do
+    it 'returns true when branch exists and commit is part of the branch' do
+      branch = described_class.new(project, double(raw))
+
+      expect(branch.exists?).to eq true
+    end
+
+    it 'returns false when branch exists and commit is not part of the branch' do
+      branch = described_class.new(project, double(raw.merge(ref: 'feature')))
+
+      expect(branch.exists?).to eq false
+    end
+
+    it 'returns false when branch does not exist' do
+      branch = described_class.new(project, double(raw.merge(ref: 'removed-branch')))
+
+      expect(branch.exists?).to eq false
+    end
+  end
+
+  describe '#repo' do
+    it 'returns raw repo' do
+      branch = described_class.new(project, double(raw))
+
+      expect(branch.repo).to eq repo
+    end
+  end
+
+  describe '#sha' do
+    it 'returns raw sha' do
+      branch = described_class.new(project, double(raw))
+
+      expect(branch.sha).to eq commit.id
+    end
+  end
+
+  describe '#valid?' do
+    it 'returns true when raw sha and ref are present' do
+      branch = described_class.new(project, double(raw))
+
+      expect(branch.valid?).to eq true
+    end
+
+    it 'returns false when raw sha is blank' do
+      branch = described_class.new(project, double(raw.merge(sha: nil)))
+
+      expect(branch.valid?).to eq false
+    end
+
+    it 'returns false when raw ref is blank' do
+      branch = described_class.new(project, double(raw.merge(ref: nil)))
+
+      expect(branch.valid?).to eq false
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/client_spec.rb b/spec/lib/gitlab/legacy_github_import/client_spec.rb
new file mode 100644
index 00000000000..80b767abce0
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/client_spec.rb
@@ -0,0 +1,97 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::Client do
+  let(:token) { '123456' }
+  let(:github_provider) { Settingslogic.new('app_id' => 'asd123', 'app_secret' => 'asd123', 'name' => 'github', 'args' => { 'client_options' => {} }) }
+
+  subject(:client) { described_class.new(token) }
+
+  before do
+    allow(Gitlab.config.omniauth).to receive(:providers).and_return([github_provider])
+  end
+
+  it 'convert OAuth2 client options to symbols' do
+    client.client.options.keys.each do |key|
+      expect(key).to be_kind_of(Symbol)
+    end
+  end
+
+  it 'does not crash (e.g. Settingslogic::MissingSetting) when verify_ssl config is not present' do
+    expect { client.api }.not_to raise_error
+  end
+
+  context 'when config is missing' do
+    before do
+      allow(Gitlab.config.omniauth).to receive(:providers).and_return([])
+    end
+
+    it 'is still possible to get an Octokit client' do
+      expect { client.api }.not_to raise_error
+    end
+
+    it 'is not be possible to get an OAuth2 client' do
+      expect { client.client }.to raise_error(Projects::ImportService::Error)
+    end
+  end
+
+  context 'allow SSL verification to be configurable on API' do
+    before do
+      github_provider['verify_ssl'] = false
+    end
+
+    it 'uses supplied value' do
+      expect(client.client.options[:connection_opts][:ssl]).to eq({ verify: false })
+      expect(client.api.connection_options[:ssl]).to eq({ verify: false })
+    end
+  end
+
+  describe '#api_endpoint' do
+    context 'when provider does not specity an API endpoint' do
+      it 'uses GitHub root API endpoint' do
+        expect(client.api.api_endpoint).to eq 'https://api.github.com/'
+      end
+    end
+
+    context 'when provider specify a custom API endpoint' do
+      before do
+        github_provider['args']['client_options']['site'] = 'https://github.company.com/'
+      end
+
+      it 'uses the custom API endpoint' do
+        expect(OmniAuth::Strategies::GitHub).not_to receive(:default_options)
+        expect(client.api.api_endpoint).to eq 'https://github.company.com/'
+      end
+    end
+
+    context 'when given a host' do
+      subject(:client) { described_class.new(token, host: 'https://try.gitea.io/') }
+
+      it 'builds a endpoint with the given host and the default API version' do
+        expect(client.api.api_endpoint).to eq 'https://try.gitea.io/api/v3/'
+      end
+    end
+
+    context 'when given an API version' do
+      subject(:client) { described_class.new(token, api_version: 'v3') }
+
+      it 'does not use the API version without a host' do
+        expect(client.api.api_endpoint).to eq 'https://api.github.com/'
+      end
+    end
+
+    context 'when given a host and version' do
+      subject(:client) { described_class.new(token, host: 'https://try.gitea.io/', api_version: 'v3') }
+
+      it 'builds a endpoint with the given options' do
+        expect(client.api.api_endpoint).to eq 'https://try.gitea.io/api/v3/'
+      end
+    end
+  end
+
+  it 'does not raise error when rate limit is disabled' do
+    stub_request(:get, /api.github.com/)
+    allow(client.api).to receive(:rate_limit!).and_raise(Octokit::NotFound)
+
+    expect { client.issues {} }.not_to raise_error
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/comment_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/comment_formatter_spec.rb
new file mode 100644
index 00000000000..413654e108c
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/comment_formatter_spec.rb
@@ -0,0 +1,96 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::CommentFormatter do
+  let(:client) { double }
+  let(:project) { create(:project) }
+  let(:octocat) { double(id: 123456, login: 'octocat', email: 'octocat@example.com') }
+  let(:created_at) { DateTime.strptime('2013-04-10T20:09:31Z') }
+  let(:updated_at) { DateTime.strptime('2014-03-03T18:58:10Z') }
+  let(:base) do
+    {
+      body: "I'm having a problem with this.",
+      user: octocat,
+      commit_id: nil,
+      diff_hunk: nil,
+      created_at: created_at,
+      updated_at: updated_at
+    }
+  end
+
+  subject(:comment) { described_class.new(project, raw, client) }
+
+  before do
+    allow(client).to receive(:user).and_return(octocat)
+  end
+
+  describe '#attributes' do
+    context 'when do not reference a portion of the diff' do
+      let(:raw) { double(base) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          project: project,
+          note: "*Created by: octocat*\n\nI'm having a problem with this.",
+          commit_id: nil,
+          line_code: nil,
+          author_id: project.creator_id,
+          type: nil,
+          created_at: created_at,
+          updated_at: updated_at
+        }
+
+        expect(comment.attributes).to eq(expected)
+      end
+    end
+
+    context 'when on a portion of the diff' do
+      let(:diff) do
+        {
+          body: 'Great stuff',
+          commit_id: '6dcb09b5b57875f334f61aebed695e2e4193db5e',
+          diff_hunk: "@@ -1,5 +1,9 @@\n class User\n   def name\n-    'John Doe'\n+    'Jane Doe'",
+          path: 'file1.txt'
+        }
+      end
+
+      let(:raw) { double(base.merge(diff)) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          project: project,
+          note: "*Created by: octocat*\n\nGreat stuff",
+          commit_id: '6dcb09b5b57875f334f61aebed695e2e4193db5e',
+          line_code: 'ce1be0ff4065a6e9415095c95f25f47a633cef2b_4_3',
+          author_id: project.creator_id,
+          type: 'LegacyDiffNote',
+          created_at: created_at,
+          updated_at: updated_at
+        }
+
+        expect(comment.attributes).to eq(expected)
+      end
+    end
+
+    context 'when author is a GitLab user' do
+      let(:raw) { double(base.merge(user: octocat)) }
+
+      it 'returns GitLab user id associated with GitHub id as author_id' do
+        gl_user = create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(comment.attributes.fetch(:author_id)).to eq gl_user.id
+      end
+
+      it 'returns GitLab user id associated with GitHub email as author_id' do
+        gl_user = create(:user, email: octocat.email)
+
+        expect(comment.attributes.fetch(:author_id)).to eq gl_user.id
+      end
+
+      it 'returns note without created at tag line' do
+        create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(comment.attributes.fetch(:note)).to eq("I'm having a problem with this.")
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/importer_spec.rb b/spec/lib/gitlab/legacy_github_import/importer_spec.rb
new file mode 100644
index 00000000000..20514486727
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/importer_spec.rb
@@ -0,0 +1,309 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::Importer do
+  shared_examples 'Gitlab::LegacyGithubImport::Importer#execute' do
+    let(:expected_not_called) { [] }
+
+    before do
+      allow(project).to receive(:import_data).and_return(double.as_null_object)
+    end
+
+    it 'calls import methods' do
+      importer = described_class.new(project)
+
+      expected_called = [
+        :import_labels, :import_milestones, :import_pull_requests, :import_issues,
+        :import_wiki, :import_releases, :handle_errors
+      ]
+
+      expected_called -= expected_not_called
+
+      aggregate_failures do
+        expected_called.each do |method_name|
+          expect(importer).to receive(method_name)
+        end
+
+        expect(importer).to receive(:import_comments).with(:issues)
+        expect(importer).to receive(:import_comments).with(:pull_requests)
+
+        expected_not_called.each do |method_name|
+          expect(importer).not_to receive(method_name)
+        end
+      end
+
+      importer.execute
+    end
+  end
+
+  shared_examples 'Gitlab::LegacyGithubImport::Importer#execute an error occurs' do
+    before do
+      allow(project).to receive(:import_data).and_return(double.as_null_object)
+
+      allow(Rails).to receive(:cache).and_return(ActiveSupport::Cache::MemoryStore.new)
+
+      allow_any_instance_of(Octokit::Client).to receive(:rate_limit!).and_raise(Octokit::NotFound)
+      allow_any_instance_of(Gitlab::Shell).to receive(:import_repository).and_raise(Gitlab::Shell::Error)
+
+      allow_any_instance_of(Octokit::Client).to receive(:user).and_return(octocat)
+      allow_any_instance_of(Octokit::Client).to receive(:labels).and_return([label1, label2])
+      allow_any_instance_of(Octokit::Client).to receive(:milestones).and_return([milestone, milestone])
+      allow_any_instance_of(Octokit::Client).to receive(:issues).and_return([issue1, issue2])
+      allow_any_instance_of(Octokit::Client).to receive(:pull_requests).and_return([pull_request, pull_request])
+      allow_any_instance_of(Octokit::Client).to receive(:issues_comments).and_return([])
+      allow_any_instance_of(Octokit::Client).to receive(:pull_requests_comments).and_return([])
+      allow_any_instance_of(Octokit::Client).to receive(:last_response).and_return(double(rels: { next: nil }))
+      allow_any_instance_of(Octokit::Client).to receive(:releases).and_return([release1, release2])
+    end
+
+    let(:label1) do
+      double(
+        name: 'Bug',
+        color: 'ff0000',
+        url: "#{api_root}/repos/octocat/Hello-World/labels/bug"
+      )
+    end
+
+    let(:label2) do
+      double(
+        name: nil,
+        color: 'ff0000',
+        url: "#{api_root}/repos/octocat/Hello-World/labels/bug"
+      )
+    end
+
+    let(:milestone) do
+      double(
+        id: 1347, # For Gitea
+        number: 1347,
+        state: 'open',
+        title: '1.0',
+        description: 'Version 1.0',
+        due_on: nil,
+        created_at: created_at,
+        updated_at: updated_at,
+        closed_at: nil,
+        url: "#{api_root}/repos/octocat/Hello-World/milestones/1"
+      )
+    end
+
+    let(:issue1) do
+      double(
+        number: 1347,
+        milestone: nil,
+        state: 'open',
+        title: 'Found a bug',
+        body: "I'm having a problem with this.",
+        assignee: nil,
+        user: octocat,
+        comments: 0,
+        pull_request: nil,
+        created_at: created_at,
+        updated_at: updated_at,
+        closed_at: nil,
+        url: "#{api_root}/repos/octocat/Hello-World/issues/1347",
+        labels: [double(name: 'Label #1')]
+      )
+    end
+
+    let(:issue2) do
+      double(
+        number: 1348,
+        milestone: nil,
+        state: 'open',
+        title: nil,
+        body: "I'm having a problem with this.",
+        assignee: nil,
+        user: octocat,
+        comments: 0,
+        pull_request: nil,
+        created_at: created_at,
+        updated_at: updated_at,
+        closed_at: nil,
+        url: "#{api_root}/repos/octocat/Hello-World/issues/1348",
+        labels: [double(name: 'Label #2')]
+      )
+    end
+
+    let(:release1) do
+      double(
+        tag_name: 'v1.0.0',
+        name: 'First release',
+        body: 'Release v1.0.0',
+        draft: false,
+        created_at: created_at,
+        updated_at: updated_at,
+        url: "#{api_root}/repos/octocat/Hello-World/releases/1"
+      )
+    end
+
+    let(:release2) do
+      double(
+        tag_name: 'v2.0.0',
+        name: 'Second release',
+        body: nil,
+        draft: false,
+        created_at: created_at,
+        updated_at: updated_at,
+        url: "#{api_root}/repos/octocat/Hello-World/releases/2"
+      )
+    end
+
+    subject { described_class.new(project) }
+
+    it 'returns true' do
+      expect(subject.execute).to eq true
+    end
+
+    it 'does not raise an error' do
+      expect { subject.execute }.not_to raise_error
+    end
+
+    it 'stores error messages' do
+      error = {
+        message: 'The remote data could not be fully imported.',
+        errors: [
+          { type: :label, url: "#{api_root}/repos/octocat/Hello-World/labels/bug", errors: "Validation failed: Title can't be blank, Title is invalid" },
+          { type: :issue, url: "#{api_root}/repos/octocat/Hello-World/issues/1348", errors: "Validation failed: Title can't be blank" },
+          { type: :wiki, errors: "Gitlab::Shell::Error" }
+        ]
+      }
+
+      unless project.gitea_import?
+        error[:errors] << { type: :release, url: "#{api_root}/repos/octocat/Hello-World/releases/2", errors: "Validation failed: Description can't be blank" }
+      end
+
+      described_class.new(project).execute
+
+      expect(project.import_error).to eq error.to_json
+    end
+  end
+
+  shared_examples 'Gitlab::LegacyGithubImport unit-testing' do
+    describe '#clean_up_restored_branches' do
+      subject { described_class.new(project) }
+
+      before do
+        allow(gh_pull_request).to receive(:source_branch_exists?).at_least(:once) { false }
+        allow(gh_pull_request).to receive(:target_branch_exists?).at_least(:once) { false }
+      end
+
+      context 'when pull request stills open' do
+        let(:gh_pull_request) { Gitlab::LegacyGithubImport::PullRequestFormatter.new(project, pull_request) }
+
+        it 'does not remove branches' do
+          expect(subject).not_to receive(:remove_branch)
+          subject.send(:clean_up_restored_branches, gh_pull_request)
+        end
+      end
+
+      context 'when pull request is closed' do
+        let(:gh_pull_request) { Gitlab::LegacyGithubImport::PullRequestFormatter.new(project, closed_pull_request) }
+
+        it 'does remove branches' do
+          expect(subject).to receive(:remove_branch).at_least(2).times
+          subject.send(:clean_up_restored_branches, gh_pull_request)
+        end
+      end
+    end
+  end
+
+  let(:project) { create(:project, :repository, :wiki_disabled, import_url: "#{repo_root}/octocat/Hello-World.git") }
+  let(:octocat) { double(id: 123456, login: 'octocat', email: 'octocat@example.com') }
+  let(:credentials) { { user: 'joe' } }
+
+  let(:created_at) { DateTime.strptime('2011-01-26T19:01:12Z') }
+  let(:updated_at) { DateTime.strptime('2011-01-27T19:01:12Z') }
+  let(:repository) { double(id: 1, fork: false) }
+  let(:source_sha) { create(:commit, project: project).id }
+  let(:source_branch) { double(ref: 'branch-merged', repo: repository, sha: source_sha, user: octocat) }
+  let(:target_sha) { create(:commit, project: project, git_commit: RepoHelpers.another_sample_commit).id }
+  let(:target_branch) { double(ref: 'master', repo: repository, sha: target_sha, user: octocat) }
+  let(:pull_request) do
+    double(
+      number: 1347,
+      milestone: nil,
+      state: 'open',
+      title: 'New feature',
+      body: 'Please pull these awesome changes',
+      head: source_branch,
+      base: target_branch,
+      assignee: nil,
+      user: octocat,
+      created_at: created_at,
+      updated_at: updated_at,
+      closed_at: nil,
+      merged_at: nil,
+      url: "#{api_root}/repos/octocat/Hello-World/pulls/1347",
+      labels: [double(name: 'Label #2')]
+    )
+  end
+  let(:closed_pull_request) do
+    double(
+      number: 1347,
+      milestone: nil,
+      state: 'closed',
+      title: 'New feature',
+      body: 'Please pull these awesome changes',
+      head: source_branch,
+      base: target_branch,
+      assignee: nil,
+      user: octocat,
+      created_at: created_at,
+      updated_at: updated_at,
+      closed_at: updated_at,
+      merged_at: nil,
+      url: "#{api_root}/repos/octocat/Hello-World/pulls/1347",
+      labels: [double(name: 'Label #2')]
+    )
+  end
+
+  context 'when importing a GitHub project' do
+    let(:api_root) { 'https://api.github.com' }
+    let(:repo_root) { 'https://github.com' }
+    subject { described_class.new(project) }
+
+    it_behaves_like 'Gitlab::LegacyGithubImport::Importer#execute'
+    it_behaves_like 'Gitlab::LegacyGithubImport::Importer#execute an error occurs'
+    it_behaves_like 'Gitlab::LegacyGithubImport unit-testing'
+
+    describe '#client' do
+      it 'instantiates a Client' do
+        allow(project).to receive(:import_data).and_return(double(credentials: credentials))
+        expect(Gitlab::LegacyGithubImport::Client).to receive(:new).with(
+          credentials[:user],
+          {}
+        )
+
+        subject.client
+      end
+    end
+  end
+
+  context 'when importing a Gitea project' do
+    let(:api_root) { 'https://try.gitea.io/api/v1' }
+    let(:repo_root) { 'https://try.gitea.io' }
+    subject { described_class.new(project) }
+
+    before do
+      project.update(import_type: 'gitea', import_url: "#{repo_root}/foo/group/project.git")
+    end
+
+    it_behaves_like 'Gitlab::LegacyGithubImport::Importer#execute' do
+      let(:expected_not_called) { [:import_releases] }
+    end
+    it_behaves_like 'Gitlab::LegacyGithubImport::Importer#execute an error occurs'
+    it_behaves_like 'Gitlab::LegacyGithubImport unit-testing'
+
+    describe '#client' do
+      it 'instantiates a Client' do
+        allow(project).to receive(:import_data).and_return(double(credentials: credentials))
+        expect(Gitlab::LegacyGithubImport::Client).to receive(:new).with(
+          credentials[:user],
+          { host: "#{repo_root}:443/foo", api_version: 'v1' }
+        )
+
+        subject.client
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/issuable_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/issuable_formatter_spec.rb
new file mode 100644
index 00000000000..3b5d8945344
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/issuable_formatter_spec.rb
@@ -0,0 +1,21 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::IssuableFormatter do
+  let(:raw_data) do
+    double(number: 42)
+  end
+  let(:project) { double(import_type: 'github') }
+  let(:issuable_formatter) { described_class.new(project, raw_data) }
+
+  describe '#project_association' do
+    it { expect { issuable_formatter.project_association }.to raise_error(NotImplementedError) }
+  end
+
+  describe '#number' do
+    it { expect(issuable_formatter.number).to eq(42) }
+  end
+
+  describe '#find_condition' do
+    it { expect(issuable_formatter.find_condition).to eq({ iid: 42 }) }
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/issue_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/issue_formatter_spec.rb
new file mode 100644
index 00000000000..1a4d5dbfb70
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/issue_formatter_spec.rb
@@ -0,0 +1,195 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::IssueFormatter do
+  let(:client) { double }
+  let!(:project) { create(:project, namespace: create(:namespace, path: 'octocat')) }
+  let(:octocat) { double(id: 123456, login: 'octocat', email: 'octocat@example.com') }
+  let(:created_at) { DateTime.strptime('2011-01-26T19:01:12Z') }
+  let(:updated_at) { DateTime.strptime('2011-01-27T19:01:12Z') }
+
+  let(:base_data) do
+    {
+      number: 1347,
+      milestone: nil,
+      state: 'open',
+      title: 'Found a bug',
+      body: "I'm having a problem with this.",
+      assignee: nil,
+      user: octocat,
+      comments: 0,
+      pull_request: nil,
+      created_at: created_at,
+      updated_at: updated_at,
+      closed_at: nil
+    }
+  end
+
+  subject(:issue) { described_class.new(project, raw_data, client) }
+
+  before do
+    allow(client).to receive(:user).and_return(octocat)
+  end
+
+  shared_examples 'Gitlab::LegacyGithubImport::IssueFormatter#attributes' do
+    context 'when issue is open' do
+      let(:raw_data) { double(base_data.merge(state: 'open')) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          iid: 1347,
+          project: project,
+          milestone: nil,
+          title: 'Found a bug',
+          description: "*Created by: octocat*\n\nI'm having a problem with this.",
+          state: 'opened',
+          author_id: project.creator_id,
+          assignee_ids: [],
+          created_at: created_at,
+          updated_at: updated_at
+        }
+
+        expect(issue.attributes).to eq(expected)
+      end
+    end
+
+    context 'when issue is closed' do
+      let(:raw_data) { double(base_data.merge(state: 'closed')) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          iid: 1347,
+          project: project,
+          milestone: nil,
+          title: 'Found a bug',
+          description: "*Created by: octocat*\n\nI'm having a problem with this.",
+          state: 'closed',
+          author_id: project.creator_id,
+          assignee_ids: [],
+          created_at: created_at,
+          updated_at: updated_at
+        }
+
+        expect(issue.attributes).to eq(expected)
+      end
+    end
+
+    context 'when it is assigned to someone' do
+      let(:raw_data) { double(base_data.merge(assignee: octocat)) }
+
+      it 'returns nil as assignee_id when is not a GitLab user' do
+        expect(issue.attributes.fetch(:assignee_ids)).to be_empty
+      end
+
+      it 'returns GitLab user id associated with GitHub id as assignee_id' do
+        gl_user = create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(issue.attributes.fetch(:assignee_ids)).to eq [gl_user.id]
+      end
+
+      it 'returns GitLab user id associated with GitHub email as assignee_id' do
+        gl_user = create(:user, email: octocat.email)
+
+        expect(issue.attributes.fetch(:assignee_ids)).to eq [gl_user.id]
+      end
+    end
+
+    context 'when it has a milestone' do
+      let(:milestone) { double(id: 42, number: 42) }
+      let(:raw_data) { double(base_data.merge(milestone: milestone)) }
+
+      it 'returns nil when milestone does not exist' do
+        expect(issue.attributes.fetch(:milestone)).to be_nil
+      end
+
+      it 'returns milestone when it exists' do
+        milestone = create(:milestone, project: project, iid: 42)
+
+        expect(issue.attributes.fetch(:milestone)).to eq milestone
+      end
+    end
+
+    context 'when author is a GitLab user' do
+      let(:raw_data) { double(base_data.merge(user: octocat)) }
+
+      it 'returns project creator_id as author_id when is not a GitLab user' do
+        expect(issue.attributes.fetch(:author_id)).to eq project.creator_id
+      end
+
+      it 'returns GitLab user id associated with GitHub id as author_id' do
+        gl_user = create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(issue.attributes.fetch(:author_id)).to eq gl_user.id
+      end
+
+      it 'returns GitLab user id associated with GitHub email as author_id' do
+        gl_user = create(:user, email: octocat.email)
+
+        expect(issue.attributes.fetch(:author_id)).to eq gl_user.id
+      end
+
+      it 'returns description without created at tag line' do
+        create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(issue.attributes.fetch(:description)).to eq("I'm having a problem with this.")
+      end
+    end
+  end
+
+  shared_examples 'Gitlab::LegacyGithubImport::IssueFormatter#number' do
+    let(:raw_data) { double(base_data.merge(number: 1347)) }
+
+    it 'returns issue number' do
+      expect(issue.number).to eq 1347
+    end
+  end
+
+  context 'when importing a GitHub project' do
+    it_behaves_like 'Gitlab::LegacyGithubImport::IssueFormatter#attributes'
+    it_behaves_like 'Gitlab::LegacyGithubImport::IssueFormatter#number'
+  end
+
+  context 'when importing a Gitea project' do
+    before do
+      project.update(import_type: 'gitea')
+    end
+
+    it_behaves_like 'Gitlab::LegacyGithubImport::IssueFormatter#attributes'
+    it_behaves_like 'Gitlab::LegacyGithubImport::IssueFormatter#number'
+  end
+
+  describe '#has_comments?' do
+    context 'when number of comments is greater than zero' do
+      let(:raw_data) { double(base_data.merge(comments: 1)) }
+
+      it 'returns true' do
+        expect(issue.has_comments?).to eq true
+      end
+    end
+
+    context 'when number of comments is equal to zero' do
+      let(:raw_data) { double(base_data.merge(comments: 0)) }
+
+      it 'returns false' do
+        expect(issue.has_comments?).to eq false
+      end
+    end
+  end
+
+  describe '#pull_request?' do
+    context 'when mention a pull request' do
+      let(:raw_data) { double(base_data.merge(pull_request: double)) }
+
+      it 'returns true' do
+        expect(issue.pull_request?).to eq true
+      end
+    end
+
+    context 'when does not mention a pull request' do
+      let(:raw_data) { double(base_data.merge(pull_request: nil)) }
+
+      it 'returns false' do
+        expect(issue.pull_request?).to eq false
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/label_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/label_formatter_spec.rb
new file mode 100644
index 00000000000..0d1d04f1bf6
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/label_formatter_spec.rb
@@ -0,0 +1,34 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::LabelFormatter do
+  let(:project) { create(:project) }
+  let(:raw) { double(name: 'improvements', color: 'e6e6e6') }
+
+  subject { described_class.new(project, raw) }
+
+  describe '#attributes' do
+    it 'returns formatted attributes' do
+      expect(subject.attributes).to eq({
+        project: project,
+        title: 'improvements',
+        color: '#e6e6e6'
+      })
+    end
+  end
+
+  describe '#create!' do
+    context 'when label does not exist' do
+      it 'creates a new label' do
+        expect { subject.create! }.to change(Label, :count).by(1)
+      end
+    end
+
+    context 'when label exists' do
+      it 'does not create a new label' do
+        Labels::CreateService.new(name: raw.name).execute(project: project)
+
+        expect { subject.create! }.not_to change(Label, :count)
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/milestone_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/milestone_formatter_spec.rb
new file mode 100644
index 00000000000..1db4bbb568c
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/milestone_formatter_spec.rb
@@ -0,0 +1,96 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::MilestoneFormatter do
+  let(:project) { create(:project) }
+  let(:created_at) { DateTime.strptime('2011-01-26T19:01:12Z') }
+  let(:updated_at) { DateTime.strptime('2011-01-27T19:01:12Z') }
+  let(:base_data) do
+    {
+      state: 'open',
+      title: '1.0',
+      description: 'Version 1.0',
+      due_on: nil,
+      created_at: created_at,
+      updated_at: updated_at,
+      closed_at: nil
+    }
+  end
+  let(:iid_attr) { :number }
+
+  subject(:formatter) { described_class.new(project, raw_data) }
+
+  shared_examples 'Gitlab::LegacyGithubImport::MilestoneFormatter#attributes' do
+    let(:data) { base_data.merge(iid_attr => 1347) }
+
+    context 'when milestone is open' do
+      let(:raw_data) { double(data.merge(state: 'open')) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          iid: 1347,
+          project: project,
+          title: '1.0',
+          description: 'Version 1.0',
+          state: 'active',
+          due_date: nil,
+          created_at: created_at,
+          updated_at: updated_at
+        }
+
+        expect(formatter.attributes).to eq(expected)
+      end
+    end
+
+    context 'when milestone is closed' do
+      let(:raw_data) { double(data.merge(state: 'closed')) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          iid: 1347,
+          project: project,
+          title: '1.0',
+          description: 'Version 1.0',
+          state: 'closed',
+          due_date: nil,
+          created_at: created_at,
+          updated_at: updated_at
+        }
+
+        expect(formatter.attributes).to eq(expected)
+      end
+    end
+
+    context 'when milestone has a due date' do
+      let(:due_date) { DateTime.strptime('2011-01-28T19:01:12Z') }
+      let(:raw_data) { double(data.merge(due_on: due_date)) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          iid: 1347,
+          project: project,
+          title: '1.0',
+          description: 'Version 1.0',
+          state: 'active',
+          due_date: due_date,
+          created_at: created_at,
+          updated_at: updated_at
+        }
+
+        expect(formatter.attributes).to eq(expected)
+      end
+    end
+  end
+
+  context 'when importing a GitHub project' do
+    it_behaves_like 'Gitlab::LegacyGithubImport::MilestoneFormatter#attributes'
+  end
+
+  context 'when importing a Gitea project' do
+    let(:iid_attr) { :id }
+    before do
+      project.update(import_type: 'gitea')
+    end
+
+    it_behaves_like 'Gitlab::LegacyGithubImport::MilestoneFormatter#attributes'
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/project_creator_spec.rb b/spec/lib/gitlab/legacy_github_import/project_creator_spec.rb
new file mode 100644
index 00000000000..737c9a624e0
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/project_creator_spec.rb
@@ -0,0 +1,80 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::ProjectCreator do
+  let(:user) { create(:user) }
+  let(:namespace) { create(:group, owner: user) }
+
+  let(:repo) do
+    OpenStruct.new(
+      login: 'vim',
+      name: 'vim',
+      full_name: 'asd/vim',
+      clone_url: 'https://gitlab.com/asd/vim.git'
+    )
+  end
+
+  subject(:service) { described_class.new(repo, repo.name, namespace, user, github_access_token: 'asdffg') }
+
+  before do
+    namespace.add_owner(user)
+    allow_any_instance_of(Project).to receive(:add_import_job)
+  end
+
+  describe '#execute' do
+    it 'creates a project' do
+      expect { service.execute }.to change(Project, :count).by(1)
+    end
+
+    it 'handle GitHub credentials' do
+      project = service.execute
+
+      expect(project.import_url).to eq('https://asdffg@gitlab.com/asd/vim.git')
+      expect(project.safe_import_url).to eq('https://*****@gitlab.com/asd/vim.git')
+      expect(project.import_data.credentials).to eq(user: 'asdffg', password: nil)
+    end
+
+    context 'when GitHub project is private' do
+      it 'sets project visibility to private' do
+        repo.private = true
+
+        project = service.execute
+
+        expect(project.visibility_level).to eq(Gitlab::VisibilityLevel::PRIVATE)
+      end
+    end
+
+    context 'when GitHub project is public' do
+      before do
+        allow_any_instance_of(ApplicationSetting).to receive(:default_project_visibility).and_return(Gitlab::VisibilityLevel::INTERNAL)
+      end
+
+      it 'sets project visibility to the default project visibility' do
+        repo.private = false
+
+        project = service.execute
+
+        expect(project.visibility_level).to eq(Gitlab::VisibilityLevel::INTERNAL)
+      end
+    end
+
+    context 'when GitHub project has wiki' do
+      it 'does not create the wiki repository' do
+        allow(repo).to receive(:has_wiki?).and_return(true)
+
+        project = service.execute
+
+        expect(project.wiki.repository_exists?).to eq false
+      end
+    end
+
+    context 'when GitHub project does not have wiki' do
+      it 'creates the wiki repository' do
+        allow(repo).to receive(:has_wiki?).and_return(false)
+
+        project = service.execute
+
+        expect(project.wiki.repository_exists?).to eq true
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/pull_request_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/pull_request_formatter_spec.rb
new file mode 100644
index 00000000000..267a41e3f32
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/pull_request_formatter_spec.rb
@@ -0,0 +1,347 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::PullRequestFormatter do
+  let(:client) { double }
+  let(:project) { create(:project, :repository) }
+  let(:source_sha) { create(:commit, project: project).id }
+  let(:target_commit) { create(:commit, project: project, git_commit: RepoHelpers.another_sample_commit) }
+  let(:target_sha) { target_commit.id }
+  let(:target_short_sha) { target_commit.id.to_s[0..7] }
+  let(:repository) { double(id: 1, fork: false) }
+  let(:source_repo) { repository }
+  let(:source_branch) { double(ref: 'branch-merged', repo: source_repo, sha: source_sha) }
+  let(:forked_source_repo) { double(id: 2, fork: true, name: 'otherproject', full_name: 'company/otherproject') }
+  let(:target_repo) { repository }
+  let(:target_branch) { double(ref: 'master', repo: target_repo, sha: target_sha, user: octocat) }
+  let(:removed_branch) { double(ref: 'removed-branch', repo: source_repo, sha: '2e5d3239642f9161dcbbc4b70a211a68e5e45e2b', user: octocat) }
+  let(:forked_branch) { double(ref: 'master', repo: forked_source_repo, sha: '2e5d3239642f9161dcbbc4b70a211a68e5e45e2b', user: octocat) }
+  let(:branch_deleted_repo) { double(ref: 'master', repo: nil, sha: '2e5d3239642f9161dcbbc4b70a211a68e5e45e2b', user: octocat) }
+  let(:octocat) { double(id: 123456, login: 'octocat', email: 'octocat@example.com') }
+  let(:created_at) { DateTime.strptime('2011-01-26T19:01:12Z') }
+  let(:updated_at) { DateTime.strptime('2011-01-27T19:01:12Z') }
+  let(:base_data) do
+    {
+      number: 1347,
+      milestone: nil,
+      state: 'open',
+      title: 'New feature',
+      body: 'Please pull these awesome changes',
+      head: source_branch,
+      base: target_branch,
+      assignee: nil,
+      user: octocat,
+      created_at: created_at,
+      updated_at: updated_at,
+      closed_at: nil,
+      merged_at: nil,
+      url: 'https://api.github.com/repos/octocat/Hello-World/pulls/1347'
+    }
+  end
+
+  subject(:pull_request) { described_class.new(project, raw_data, client) }
+
+  before do
+    allow(client).to receive(:user).and_return(octocat)
+  end
+
+  shared_examples 'Gitlab::LegacyGithubImport::PullRequestFormatter#attributes' do
+    context 'when pull request is open' do
+      let(:raw_data) { double(base_data.merge(state: 'open')) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          iid: 1347,
+          title: 'New feature',
+          description: "*Created by: octocat*\n\nPlease pull these awesome changes",
+          source_project: project,
+          source_branch: 'branch-merged',
+          source_branch_sha: source_sha,
+          target_project: project,
+          target_branch: 'master',
+          target_branch_sha: target_sha,
+          state: 'opened',
+          milestone: nil,
+          author_id: project.creator_id,
+          assignee_id: nil,
+          created_at: created_at,
+          updated_at: updated_at,
+          imported: true
+        }
+
+        expect(pull_request.attributes).to eq(expected)
+      end
+    end
+
+    context 'when pull request is closed' do
+      let(:raw_data) { double(base_data.merge(state: 'closed')) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          iid: 1347,
+          title: 'New feature',
+          description: "*Created by: octocat*\n\nPlease pull these awesome changes",
+          source_project: project,
+          source_branch: 'branch-merged',
+          source_branch_sha: source_sha,
+          target_project: project,
+          target_branch: 'master',
+          target_branch_sha: target_sha,
+          state: 'closed',
+          milestone: nil,
+          author_id: project.creator_id,
+          assignee_id: nil,
+          created_at: created_at,
+          updated_at: updated_at,
+          imported: true
+        }
+
+        expect(pull_request.attributes).to eq(expected)
+      end
+    end
+
+    context 'when pull request is merged' do
+      let(:merged_at) { DateTime.strptime('2011-01-28T13:01:12Z') }
+      let(:raw_data) { double(base_data.merge(state: 'closed', merged_at: merged_at)) }
+
+      it 'returns formatted attributes' do
+        expected = {
+          iid: 1347,
+          title: 'New feature',
+          description: "*Created by: octocat*\n\nPlease pull these awesome changes",
+          source_project: project,
+          source_branch: 'branch-merged',
+          source_branch_sha: source_sha,
+          target_project: project,
+          target_branch: 'master',
+          target_branch_sha: target_sha,
+          state: 'merged',
+          milestone: nil,
+          author_id: project.creator_id,
+          assignee_id: nil,
+          created_at: created_at,
+          updated_at: updated_at,
+          imported: true
+        }
+
+        expect(pull_request.attributes).to eq(expected)
+      end
+    end
+
+    context 'when it is assigned to someone' do
+      let(:raw_data) { double(base_data.merge(assignee: octocat)) }
+
+      it 'returns nil as assignee_id when is not a GitLab user' do
+        expect(pull_request.attributes.fetch(:assignee_id)).to be_nil
+      end
+
+      it 'returns GitLab user id associated with GitHub id as assignee_id' do
+        gl_user = create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(pull_request.attributes.fetch(:assignee_id)).to eq gl_user.id
+      end
+
+      it 'returns GitLab user id associated with GitHub email as assignee_id' do
+        gl_user = create(:user, email: octocat.email)
+
+        expect(pull_request.attributes.fetch(:assignee_id)).to eq gl_user.id
+      end
+    end
+
+    context 'when author is a GitLab user' do
+      let(:raw_data) { double(base_data.merge(user: octocat)) }
+
+      it 'returns project creator_id as author_id when is not a GitLab user' do
+        expect(pull_request.attributes.fetch(:author_id)).to eq project.creator_id
+      end
+
+      it 'returns GitLab user id associated with GitHub id as author_id' do
+        gl_user = create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(pull_request.attributes.fetch(:author_id)).to eq gl_user.id
+      end
+
+      it 'returns GitLab user id associated with GitHub email as author_id' do
+        gl_user = create(:user, email: octocat.email)
+
+        expect(pull_request.attributes.fetch(:author_id)).to eq gl_user.id
+      end
+
+      it 'returns description without created at tag line' do
+        create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(pull_request.attributes.fetch(:description)).to eq('Please pull these awesome changes')
+      end
+    end
+
+    context 'when it has a milestone' do
+      let(:milestone) { double(id: 42, number: 42) }
+      let(:raw_data) { double(base_data.merge(milestone: milestone)) }
+
+      it 'returns nil when milestone does not exist' do
+        expect(pull_request.attributes.fetch(:milestone)).to be_nil
+      end
+
+      it 'returns milestone when it exists' do
+        milestone = create(:milestone, project: project, iid: 42)
+
+        expect(pull_request.attributes.fetch(:milestone)).to eq milestone
+      end
+    end
+  end
+
+  shared_examples 'Gitlab::LegacyGithubImport::PullRequestFormatter#number' do
+    let(:raw_data) { double(base_data) }
+
+    it 'returns pull request number' do
+      expect(pull_request.number).to eq 1347
+    end
+  end
+
+  shared_examples 'Gitlab::LegacyGithubImport::PullRequestFormatter#source_branch_name' do
+    context 'when source branch exists' do
+      let(:raw_data) { double(base_data) }
+
+      it 'returns branch ref' do
+        expect(pull_request.source_branch_name).to eq 'branch-merged'
+      end
+    end
+
+    context 'when source branch does not exist' do
+      let(:raw_data) { double(base_data.merge(head: removed_branch)) }
+
+      it 'prefixes branch name with gh-:short_sha/:number/:user pattern to avoid collision' do
+        expect(pull_request.source_branch_name).to eq "gh-#{target_short_sha}/1347/octocat/removed-branch"
+      end
+    end
+
+    context 'when source branch is from a fork' do
+      let(:raw_data) { double(base_data.merge(head: forked_branch)) }
+
+      it 'prefixes branch name with gh-:short_sha/:number/:user pattern to avoid collision' do
+        expect(pull_request.source_branch_name).to eq "gh-#{target_short_sha}/1347/octocat/master"
+      end
+    end
+
+    context 'when source branch is from a deleted fork' do
+      let(:raw_data) { double(base_data.merge(head: branch_deleted_repo)) }
+
+      it 'prefixes branch name with gh-:short_sha/:number/:user pattern to avoid collision' do
+        expect(pull_request.source_branch_name).to eq "gh-#{target_short_sha}/1347/octocat/master"
+      end
+    end
+  end
+
+  shared_examples 'Gitlab::LegacyGithubImport::PullRequestFormatter#target_branch_name' do
+    context 'when target branch exists' do
+      let(:raw_data) { double(base_data) }
+
+      it 'returns branch ref' do
+        expect(pull_request.target_branch_name).to eq 'master'
+      end
+    end
+
+    context 'when target branch does not exist' do
+      let(:raw_data) { double(base_data.merge(base: removed_branch)) }
+
+      it 'prefixes branch name with gh-:short_sha/:number/:user pattern to avoid collision' do
+        expect(pull_request.target_branch_name).to eq 'gl-2e5d3239/1347/octocat/removed-branch'
+      end
+    end
+  end
+
+  context 'when importing a GitHub project' do
+    it_behaves_like 'Gitlab::LegacyGithubImport::PullRequestFormatter#attributes'
+    it_behaves_like 'Gitlab::LegacyGithubImport::PullRequestFormatter#number'
+    it_behaves_like 'Gitlab::LegacyGithubImport::PullRequestFormatter#source_branch_name'
+    it_behaves_like 'Gitlab::LegacyGithubImport::PullRequestFormatter#target_branch_name'
+  end
+
+  context 'when importing a Gitea project' do
+    before do
+      project.update(import_type: 'gitea')
+    end
+
+    it_behaves_like 'Gitlab::LegacyGithubImport::PullRequestFormatter#attributes'
+    it_behaves_like 'Gitlab::LegacyGithubImport::PullRequestFormatter#number'
+    it_behaves_like 'Gitlab::LegacyGithubImport::PullRequestFormatter#source_branch_name'
+    it_behaves_like 'Gitlab::LegacyGithubImport::PullRequestFormatter#target_branch_name'
+  end
+
+  describe '#valid?' do
+    context 'when source, and target repos are not a fork' do
+      let(:raw_data) { double(base_data) }
+
+      it 'returns true' do
+        expect(pull_request.valid?).to eq true
+      end
+    end
+
+    context 'when source repo is a fork' do
+      let(:source_repo) { double(id: 2) }
+      let(:raw_data) { double(base_data) }
+
+      it 'returns true' do
+        expect(pull_request.valid?).to eq true
+      end
+    end
+
+    context 'when target repo is a fork' do
+      let(:target_repo) { double(id: 2) }
+      let(:raw_data) { double(base_data) }
+
+      it 'returns true' do
+        expect(pull_request.valid?).to eq true
+      end
+    end
+  end
+
+  describe '#cross_project?' do
+    context 'when source and target repositories are different' do
+      let(:raw_data) { double(base_data.merge(head: forked_branch)) }
+
+      it 'returns true' do
+        expect(pull_request.cross_project?).to eq true
+      end
+    end
+
+    context 'when source repository does not exist anymore' do
+      let(:raw_data) { double(base_data.merge(head: branch_deleted_repo)) }
+
+      it 'returns true' do
+        expect(pull_request.cross_project?).to eq true
+      end
+    end
+
+    context 'when source and target repositories are the same' do
+      let(:raw_data) { double(base_data.merge(head: source_branch)) }
+
+      it 'returns false' do
+        expect(pull_request.cross_project?).to eq false
+      end
+    end
+  end
+
+  describe '#source_branch_exists?' do
+    let(:raw_data) { double(base_data.merge(head: forked_branch)) }
+
+    it 'returns false when is a cross_project' do
+      expect(pull_request.source_branch_exists?).to eq false
+    end
+  end
+
+  describe '#url' do
+    let(:raw_data) { double(base_data) }
+
+    it 'return raw url' do
+      expect(pull_request.url).to eq 'https://api.github.com/repos/octocat/Hello-World/pulls/1347'
+    end
+  end
+
+  describe '#opened?' do
+    let(:raw_data) { double(base_data.merge(state: 'open')) }
+
+    it 'returns true when state is "open"' do
+      expect(pull_request.opened?).to be_truthy
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/release_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/release_formatter_spec.rb
new file mode 100644
index 00000000000..082e3b36dd0
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/release_formatter_spec.rb
@@ -0,0 +1,54 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::ReleaseFormatter do
+  let!(:project) { create(:project, namespace: create(:namespace, path: 'octocat')) }
+  let(:octocat) { double(id: 123456, login: 'octocat') }
+  let(:created_at) { DateTime.strptime('2011-01-26T19:01:12Z') }
+
+  let(:base_data) do
+    {
+      tag_name: 'v1.0.0',
+      name: 'First release',
+      draft: false,
+      created_at: created_at,
+      published_at: created_at,
+      body: 'Release v1.0.0'
+    }
+  end
+
+  subject(:release) { described_class.new(project, raw_data) }
+
+  describe '#attributes' do
+    let(:raw_data) { double(base_data) }
+
+    it 'returns formatted attributes' do
+      expected = {
+        project: project,
+        tag: 'v1.0.0',
+        description: 'Release v1.0.0',
+        created_at: created_at,
+        updated_at: created_at
+      }
+
+      expect(release.attributes).to eq(expected)
+    end
+  end
+
+  describe '#valid' do
+    context 'when release is not a draft' do
+      let(:raw_data) { double(base_data) }
+
+      it 'returns true' do
+        expect(release.valid?).to eq true
+      end
+    end
+
+    context 'when release is draft' do
+      let(:raw_data) { double(base_data.merge(draft: true)) }
+
+      it 'returns false' do
+        expect(release.valid?).to eq false
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/user_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/user_formatter_spec.rb
new file mode 100644
index 00000000000..3cd096eb0ad
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/user_formatter_spec.rb
@@ -0,0 +1,39 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::UserFormatter do
+  let(:client) { double }
+  let(:octocat) { double(id: 123456, login: 'octocat', email: 'octocat@example.com') }
+
+  subject(:user) { described_class.new(client, octocat) }
+
+  before do
+    allow(client).to receive(:user).and_return(octocat)
+  end
+
+  describe '#gitlab_id' do
+    context 'when GitHub user is a GitLab user' do
+      it 'return GitLab user id when user associated their account with GitHub' do
+        gl_user = create(:omniauth_user, extern_uid: octocat.id, provider: 'github')
+
+        expect(user.gitlab_id).to eq gl_user.id
+      end
+
+      it 'returns GitLab user id when user primary email matches GitHub email' do
+        gl_user = create(:user, email: octocat.email)
+
+        expect(user.gitlab_id).to eq gl_user.id
+      end
+
+      it 'returns GitLab user id when any of user linked emails matches GitHub email' do
+        gl_user = create(:user, email: 'johndoe@example.com')
+        create(:email, user: gl_user, email: octocat.email)
+
+        expect(user.gitlab_id).to eq gl_user.id
+      end
+    end
+
+    it 'returns nil when GitHub user is not a GitLab user' do
+      expect(user.gitlab_id).to be_nil
+    end
+  end
+end
diff --git a/spec/lib/gitlab/legacy_github_import/wiki_formatter_spec.rb b/spec/lib/gitlab/legacy_github_import/wiki_formatter_spec.rb
new file mode 100644
index 00000000000..7723533aee2
--- /dev/null
+++ b/spec/lib/gitlab/legacy_github_import/wiki_formatter_spec.rb
@@ -0,0 +1,23 @@
+require 'spec_helper'
+
+describe Gitlab::LegacyGithubImport::WikiFormatter do
+  let(:project) do
+    create(:project,
+           namespace: create(:namespace, path: 'gitlabhq'),
+           import_url: 'https://xxx@github.com/gitlabhq/sample.gitlabhq.git')
+  end
+
+  subject(:wiki) { described_class.new(project) }
+
+  describe '#disk_path' do
+    it 'appends .wiki to project path' do
+      expect(wiki.disk_path).to eq project.wiki.disk_path
+    end
+  end
+
+  describe '#import_url' do
+    it 'returns URL of the wiki repository' do
+      expect(wiki.import_url).to eq 'https://xxx@github.com/gitlabhq/sample.gitlabhq.wiki.git'
+    end
+  end
+end