Some EC2 Tests

lib/cloudscopes/ec2.rb

@@ -1,11 +1,7 @@
 require 'net/http'
 
 module Cloudscopes
-
   class Ec2
-
-    @@baseurl = 'http://169.254.169.254/latest/meta-data'
-
     HYPERVISOR_UUID_PATH = '/sys/hypervisor/uuid'.freeze
     DMI_PRODUCT_UUID_PATH = '/sys/devices/virtual/dmi/id/product_uuid'.freeze
 
@@ -22,13 +18,17 @@ def self.runs_on_ec2?
     end
 
     def instance_id
-      @@instanceid ||= Net::HTTP.get(URI("#{@@baseurl}/instance-id"))
+      @@instance_id ||= get_metadata('instance-id')
     end
 
     def availability_zone
-      @@az ||= Net::HTTP.get(URI("#{@@baseurl}/placement/availability-zone"))
+      @@availability_zone ||= get_metadata('placement/availability-zone')
     end
 
-  end
+    private
 
+    def get_metadata(path)
+      Net::HTTP.get(URI("http://169.254.169.254/latest/meta-data/#{path}"))
+    end
+  end
 end

spec/ec2_spec.rb

@@ -0,0 +1,101 @@
+module Cloudscopes
+
+RSpec.describe Ec2 do
+  subject(:ec2) { Ec2.new }
+
+  describe ".runs_on_ec2?" do
+    subject(:runs_on_ec2?) { Ec2.runs_on_ec2? }
+    let(:hypervisor_uuid) { nil }
+    let(:dmi_product_uuid) { nil }
+
+    before do
+      allow(File).to receive(:exists?).and_return(false)
+      if hypervisor_uuid
+        path = '/sys/hypervisor/uuid'
+        allow(File).to receive(:exists?).with(path).and_return(true)
+        allow(File).to receive(:read).with(path).and_return(hypervisor_uuid)
+      end
+      if dmi_product_uuid
+        path = '/sys/devices/virtual/dmi/id/product_uuid'
+        allow(File).to receive(:exists?).with(path).and_return(true)
+        allow(File).to receive(:read).with(path).and_return(dmi_product_uuid)
+      end
+    end
+
+    context "on non EC2 instance" do
+      it { is_expected.to be false }
+
+      context "which has hypervisor UUID" do
+        let(:hypervisor_uuid) { 'non-ec2' }
+
+        it { is_expected.to be false }
+      end
+
+      context "which has no hypervisor UUID but DMI product UUID" do
+        let(:dmi_product_uuid) { 'non-ec2' }
+
+        it { is_expected.to be false }
+      end
+    end
+
+    context "on EC2 instance" do
+      context "which has hypervisor UUID" do
+        let(:hypervisor_uuid) { 'ec2whatever' }
+
+        it { is_expected.to be true }
+      end
+
+      context "which has no hypervisor UUID but DMI product UUID" do
+        let(:dmi_product_uuid) { 'EC2WHATEVER' }
+
+        it { is_expected.to be true }
+      end
+    end
+  end
+
+  describe "#instance_id" do
+    subject(:instance_id) { ec2.instance_id }
+
+    # current implementation uses class variable
+    # unset it here to avoid side-effects
+    before { Ec2.class_variable_set('@@instance_id', nil) }
+
+    it "delivers the instance ID from the instance's metadata" do
+      expect(Net::HTTP).
+          to receive(:get).with(URI("http://169.254.169.254/latest/meta-data/instance-id")).
+          and_return("metadata instance ID")
+      expect(ec2.instance_id).to eq("metadata instance ID")
+    end
+
+    it "does not lookup twice" do
+      expect(Net::HTTP).to receive(:get).exactly(:once).and_return("instance ID")
+      expect(ec2.instance_id).to eq("instance ID")
+      expect(ec2.instance_id).to eq("instance ID")
+      expect(ec2.instance_id).to eq("instance ID")
+    end
+  end
+
+  describe "#availability_zone" do
+    subject(:availability_zone) { ec2.availability_zone }
+
+    # current implementation uses class variable
+    # unset it here to avoid side-effects
+    before { Ec2.class_variable_set('@@availability_zone', nil) }
+
+    it "delivers the availability zone from the instance's metadata" do
+      expect(Net::HTTP).to receive(:get).
+          with(URI("http://169.254.169.254/latest/meta-data/placement/availability-zone")).
+          and_return("metadata AZ")
+      expect(ec2.availability_zone).to eq("metadata AZ")
+    end
+
+    it "does not lookup twice" do
+      expect(Net::HTTP).to receive(:get).exactly(:once).and_return("AZ")
+      expect(ec2.availability_zone).to eq("AZ")
+      expect(ec2.availability_zone).to eq("AZ")
+      expect(ec2.availability_zone).to eq("AZ")
+    end
+  end
+end
+
+end