Add test for writing disk_meta file

test/unit/vagrant/action/builtin/disk_test.rb

@@ -5,13 +5,16 @@ describe Vagrant::Action::Builtin::Disk do
   let(:vm) { double("vm") }
   let(:config) { double("config", vm: vm) }
   let(:provider) { double("provider") }
-  let(:machine) { double("machine", config: config, provider: provider, provider_name: "provider") }
+  let(:machine) { double("machine", config: config, provider: provider,
+                         provider_name: "provider", data_dir: Pathname.new("/fake/dir")) }
   let(:env) { { ui: ui, machine: machine} }
 
   let(:disks) { [double("disk")] }
 
   let(:ui)  { double("ui") }
 
+  let(:disk_data) { {disk: [{uuid: "123456789", name: "storage"}], floppy: [], dvd: []} }
+
   describe "#call" do
     it "calls configure_disks if disk config present" do
       allow(vm).to receive(:disks).and_return(disks)
@@ -20,7 +23,10 @@ describe Vagrant::Action::Builtin::Disk do
       subject = described_class.new(app, env)
 
       expect(app).to receive(:call).with(env).ordered
-      expect(machine.provider).to receive(:capability).with(:configure_disks, disks).and_return({})
+      expect(machine.provider).to receive(:capability).
+        with(:configure_disks, disks).and_return(disk_data)
+
+      expect(subject).to receive(:write_disk_metadata).and_return(true)
 
       subject.call(env)
     end
@@ -32,6 +38,8 @@ describe Vagrant::Action::Builtin::Disk do
       expect(app).to receive(:call).with(env).ordered
       expect(machine.provider).not_to receive(:capability).with(:configure_disks, disks)
 
+      expect(subject).not_to receive(:write_disk_metadata)
+
       subject.call(env)
     end
 
@@ -46,5 +54,13 @@ describe Vagrant::Action::Builtin::Disk do
 
       subject.call(env)
     end
+
+    it "writes down a disk_meta file if disks are configured" do
+      subject = described_class.new(app, env)
+
+      expect(File).to receive(:open).with("/fake/dir/disk_meta", "w+").and_return(true)
+
+      subject.write_disk_metadata(machine, disk_data)
+    end
   end
 end