commands/plugin: fix plugin existence middleware, add tests

plugins/commands/plugin/action/plugin_exists_check.rb

@@ -11,7 +11,7 @@ module VagrantPlugins
         end
 
         def call(env)
-          installed = Vagrant::Plugin::Manager.instance.installed_specs
+          installed = Vagrant::Plugin::Manager.instance.installed_plugins
           if !installed.has_key?(env[:plugin_name])
             raise Vagrant::Errors::PluginNotInstalled,
               name: env[:plugin_name]

test/unit/plugins/commands/plugin/action/plugin_exists_check_test.rb

@@ -0,0 +1,31 @@
+require File.expand_path("../../../../../base", __FILE__)
+
+describe VagrantPlugins::CommandPlugin::Action::PluginExistsCheck do
+  let(:app) { lambda {} }
+  let(:env) { {} }
+
+  let(:manager) { double("manager") }
+
+  subject { described_class.new(app, env) }
+
+  before do
+    Vagrant::Plugin::Manager.stub(instance: manager)
+  end
+
+  it "should raise an exception if the plugin doesn't exist" do
+    manager.stub(installed_plugins: { "foo" => {} })
+    app.should_not_receive(:call)
+
+    env[:plugin_name] = "bar"
+    expect { subject.call(env) }.
+      to raise_error(Vagrant::Errors::PluginNotInstalled)
+  end
+
+  it "should call the app if the plugin is installed" do
+    manager.stub(installed_plugins: { "bar" => {} })
+    app.should_receive(:call).once.with(env)
+
+    env[:plugin_name] = "bar"
+    subject.call(env)
+  end
+end