Number and string accept an environment as well

lib/chervil/ast/number.rb

       @value = value
     end
 
-    def evaluate
+    def evaluate(env)
       @value
     end
 

lib/chervil/ast/string.rb

       @value == other.value
     end
 
-    def evaluate
+    def evaluate(env)
       @value
     end
   end

spec/ast/number_spec.rb

-module Chervil::AST
-  RSpec.describe Number do
+module Chervil
+  RSpec.describe AST::Number do
     it 'evaluates' do
-      expect(Number.new(5.0).evaluate).to eq(5.0)
+      expect(AST::Number.new(5.0).evaluate(Env.new)).to eq(5.0)
     end
   end
 end

spec/ast/string_spec.rb

-module Chervil::AST
-  RSpec.describe String do
+module Chervil
+  RSpec.describe AST::String do
     it 'evaluates' do
-      expect(String.new("hello world").evaluate).to eq("hello world")
+      expect(AST::String.new("hello world").evaluate(Env.new)).to eq("hello world")
     end
   end
 end