Add authentication specs

.gitignore

@@ -56,3 +56,4 @@ build-iPhoneSimulator/
 # .rubocop-https?--*
 
 Gemfile.lock
+.rspec_status

.rspec

@@ -0,0 +1 @@
+--require spec_helper

spec/client_spec.rb

@@ -0,0 +1,49 @@
+RSpec.describe ServiceNow::Client do
+  let(:instance_id)   { "instance_id_foo" }
+  let(:client_id)     { "client_id_foo" }
+  let(:client_secret) { "client_secret_foo" }
+  let(:username)      { "some_user" }
+  let(:password)      { "p4ssw0rd" }
+  let(:refresh_token) { "refresh_token_foo" }
+
+  let(:connection)    { double(Faraday) }
+  let(:response)      { double(Faraday::Response, body: {"access_token" => "access_token_foo"}) }
+
+  describe ".authenticate" do
+    it "connects" do
+      expect(Faraday).to receive(:new).with({url: "https://#{instance_id}.service-now.com/"}).and_return(connection)
+      expect(connection).to receive(:post).with("oauth_token.do",
+        {
+          client_id: client_id,
+          client_secret: client_secret,
+          grant_type: "password",
+          username: username,
+          password: password
+        }
+      ).and_return(response)
+
+      client = described_class.authenticate(instance_id, client_id, client_secret, username, password)
+
+      expect(client).to be_a(described_class)
+    end
+  end
+
+  describe ".authenticate_with_refresh_token" do
+    it "connects" do
+      expect(Faraday).to receive(:new).with({url: "https://#{instance_id}.service-now.com/"}).and_return(connection)
+      expect(connection).to receive(:post).with("oauth_token.do",
+        {
+          client_id: client_id,
+          client_secret: client_secret,
+          grant_type: "refresh_token",
+          refresh_token: refresh_token,
+          scope: "useraccount"
+        }
+      ).and_return(response)
+
+      client = described_class.authenticate_with_refresh_token(instance_id, client_id, client_secret, refresh_token)
+
+      expect(client).to be_a(described_class)
+    end
+  end
+end