Add "strict attribute" mode for testing templates

diff --git a/lib/inversion/template.rb b/lib/inversion/template.rb
--- a/lib/inversion/template.rb
+++ b/lib/inversion/template.rb
@@ -121,6 +121,7 @@ class Inversion::Template
 		:ignore_unknown_tags => true,
 		:template_paths      => [],
 		:stat_delay          => 0,
+		:strict_attributes   => false,
 
 		# Rendering options
 		:on_render_error     => :comment,
@@ -391,6 +392,10 @@ class Inversion::Template
 	def method_missing( sym, *args, &block )
 		return super unless sym.to_s =~ /^([a-z]\w+)=?$/i
 		attribute = $1
+
+		raise NoMethodError, "no tag attribute '%s' (strict mode)" % [ attribute ] if
+			self.options[:strict_attributes]
+
 		self.install_accessors( attribute )
 
 		# Call the new method via #method to avoid a method_missing loop.
diff --git a/spec/inversion/template_spec.rb b/spec/inversion/template_spec.rb
--- a/spec/inversion/template_spec.rb
+++ b/spec/inversion/template_spec.rb
@@ -65,6 +65,7 @@ describe Inversion::Template do
 		tmpl.render( &renderblock )
 	end
 
+
 	it "carries its global configuration to the parser" do
 		begin
 			orig_config = described_class.config
@@ -78,6 +79,7 @@ describe Inversion::Template do
 		end
 	end
 
+
 	it "carries its global configuration to per-template options" do
 		begin
 			orig_config = described_class.config
@@ -103,6 +105,7 @@ describe Inversion::Template do
 		expect( tmpl.inspect ).to_not match( /node_tree/ )
 	end
 
+
 	it "includes the node tree in the inspected object if debugging is enabled" do
 		begin
 			debuglevel = $DEBUG
@@ -115,12 +118,21 @@ describe Inversion::Template do
 		end
 	end
 
+
 	it "provides accessors for attributes that aren't identifiers in the template" do
 		tmpl = described_class.new( '' )
 		tmpl.foo = :bar
 		expect( tmpl.foo ).to eq( :bar )
 	end
 
+
+	it "raises instead of generating an accessor if configured with strict attributes" do
+		tmpl = described_class.new( '', strict_attributes: true )
+		expect { tmpl.foo = :bar }.to raise_error( NoMethodError, "no tag attribute 'foo' (strict mode)" )
+		expect { tmpl.foo }.to raise_error( NoMethodError, "no tag attribute 'foo' (strict mode)")
+	end
+
+
 	it "can pass an encoding option to IO.open through the template constructor" do
 		content = 'some stuff'.encode( 'utf-8' )
 		expect( IO ).to receive( :read ).with( '/a/utf8/template.tmpl', encoding: 'utf-8' ).and_return( content )
@@ -270,7 +282,6 @@ describe Inversion::Template do
 	end
 
 
-
 	context "without template paths set" do
 
 		before( :each ) do