Add a client cert spec for the http client

spec/jira/http_client_spec.rb

@@ -28,6 +28,15 @@
     JIRA::HttpClient.new(options)
   end
 
+  let(:basic_client_cert_client) do
+    options = JIRA::Client::DEFAULT_OPTIONS.merge(JIRA::HttpClient::DEFAULT_OPTIONS).merge(
+      :use_client_cert => true,
+      :cert => 'public certificate contents',
+      :key => 'private key contents'
+    )
+    JIRA::HttpClient.new(options)
+  end
+
   let(:response) do
     response = double("response")
     allow(response).to receive(:kind_of?).with(Net::HTTPSuccess).and_return(true)
@@ -170,6 +179,22 @@
     expect(basic_client.http_conn(uri)).to eq(http_conn)
   end
 
+  it 'can use client certificates' do
+    http_conn = double
+    uri = double
+    host = double
+    port = double
+    expect(Net::HTTP).to receive(:new).with(host, port).and_return(http_conn)
+    expect(uri).to receive(:host).and_return(host)
+    expect(uri).to receive(:port).and_return(port)
+    expect(http_conn).to receive(:use_ssl=).with(basic_client.options[:use_ssl])
+    expect(http_conn).to receive(:verify_mode=).with(basic_client.options[:ssl_verify_mode])
+    expect(http_conn).to receive(:read_timeout=).with(basic_client.options[:read_timeout])
+    expect(http_conn).to receive(:cert=).with(basic_client_cert_client.options[:cert])
+    expect(http_conn).to receive(:key=).with(basic_client_cert_client.options[:key])
+    expect(basic_client_cert_client.http_conn(uri)).to eq(http_conn)
+  end
+
   it "returns a http connection" do
     http_conn = double()
     uri = double()