specify methods all backends must implement

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>

lib/vulcano/plugins/backend.rb

@@ -10,7 +10,18 @@ module Vulcano::Plugins
     end
 
     def self.__register(name, obj)
-      Vulcano::Backend.registry[name] = obj
+      cl = Class.new(obj) do
+        include BackendCommon
+      end
+      Vulcano::Backend.registry[name] = cl
+    end
+
+    module BackendCommon
+      %w{ file run_command os }.each do |name|
+        define_method name do |*args|
+          raise NotImplementedError.new("Backend must implement the #{name}() method.")
+        end
+      end
     end
 
     class FileCommon
@@ -47,27 +58,27 @@ module Vulcano::Plugins
       end
 
       def block_device?
-        @file.type == :block_device
+        type == :block_device
       end
 
       def character_device?
-        @file.type == :character_device
+        type == :character_device
       end
 
       def socket?
-        @file.type == :socket
+        type == :socket
       end
 
       def directory?
-        @file.type == :directory
+        type == :directory
       end
 
       def symlink?
-        @file.type == :symlink
+        type == :symlink
       end
 
       def pipe?
-        @file.type == :pipe?
+        type == :pipe?
       end
 
       def mode?(mode)

test/unit/plugins_v1_backend_test.rb

@@ -8,12 +8,37 @@ describe 'Vulcano::Plugins::Backend' do
 
   it 'provides a name method for registering' do
     @child.must_respond_to :name
-    @child.name 'test'
-    # check if it's there
-    reg = Vulcano::Backend.registry
-    reg.keys.must_include 'test'
-    reg['test'].must_equal @child
-    # cleanup
-    reg.delete('test')
   end
+
+  describe 'when registering a plugin' do
+    before do
+      @child.name 'test'
+      @reg = Vulcano::Backend.registry
+    end
+
+    after do
+      @reg.delete('test')
+    end
+
+    it 'must have the backend registered' do
+      @reg.keys.must_include 'test'
+      @reg['test'].ancestors[2].must_equal @child
+    end
+
+    it 'must raise an error if file is not implemented' do
+      t = @reg['test'].new
+      proc { t.run_command }.must_raise NotImplementedError
+    end
+
+    it 'must raise an error if run_command is not implemented' do
+      t = @reg['test'].new
+      proc { t.file }.must_raise NotImplementedError
+    end
+
+    it 'must raise an error if os is not implemented' do
+      t = @reg['test'].new
+      proc { t.os }.must_raise NotImplementedError
+    end
+  end
+
 end