Add unit test and documentation for playbook_command option

test/unit/plugins/provisioners/ansible/config/shared.rb

@@ -12,6 +12,7 @@ shared_examples_for 'options shared by both Ansible provisioners' do
     expect(subject.inventory_path).to be_nil
     expect(subject.limit).to be_nil
     expect(subject.playbook).to be_nil
+    expect(subject.playbook_command).to eql("ansible-playbook")
     expect(subject.raw_arguments).to be_nil
     expect(subject.skip_tags).to be_nil
     expect(subject.start_at_task).to be_nil

test/unit/plugins/provisioners/ansible/provisioner_test.rb

@@ -273,6 +273,18 @@ VF
       end
     end
 
+    describe "with playbook_command option" do
+      before do
+        config.playbook_command = "custom-ansible-playbook"
+      end
+
+      it "uses custom playbook_command to run playbooks" do
+        expect(Vagrant::Util::Subprocess).to receive(:execute).with { |*args|
+          expect(args[0]).to eq("custom-ansible-playbook")
+        }
+      end
+    end
+
     describe "with host_vars option" do
       it_should_create_and_use_generated_inventory
 

website/source/docs/provisioning/ansible_common.html.md

@@ -78,6 +78,10 @@ Some of these options are for advanced usage only and should not be used unless
 
     By default, this option is disabled and Vagrant generates an inventory based on the `Vagrantfile` information.
 
+- `playbook_command` (string) - The command used to run playbooks.
+
+   The default value is `ansible-playbook`
+
 - `galaxy_command` (template string) - The command pattern used to install Galaxy roles when `galaxy_role_file` is set.
 
     The following (optional) placeholders can be used in this command pattern: