Test legacy template tags

lib/phlex/sgml.rb

@@ -75,7 +75,7 @@ def template
 
 		def self.method_added(method_name)
 			if method_name == :template
-				warn "Defining the `template` method on a Phlex component is deprecated and will be unsupported in Phlex 2.0. Please define `view_template` instead."
+				Kernel.warn "Defining the `template` method on a Phlex component is deprecated and will be unsupported in Phlex 2.0. Please define `view_template` instead."
 			end
 		end
 

test/phlex/view/legacy_template_method.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+describe Phlex::SGML do
+	it "warns when you define a template" do
+		expect(Kernel).to receive(:warn)
+
+		class Example < Phlex::HTML
+			def template
+				h1 { "Hello, world!" }
+			end
+		end
+
+		expect(
+			Example.new.call
+		).to be == "<h1>Hello, world!</h1>"
+	end
+end