Test scoping

lib/ahem/ast/function_call.rb

   end
 
   def execute(env)
+    env = Environment.new(env)
     function = env.get(@function.name)
 
     if function.is_a?(AST::FunctionDefinition)

spec/ast/function_call_spec.rb

       ).execute(env)
     ).to eq(120.0)
   end
+
+  # This is equivalent to the program
+  #
+  # function add_one(n) {
+  #   n + 1;
+  # }
+  # add_one(5);
+  # print(n);
+  #
+  # This test is ensuring that `n` is not still defined outside the scope of
+  # add_one after the function finishes executing
+  it 'destroys variables when they go out of scope' do
+    env = Environment.new
+    AST::FunctionDefinition.new(
+      AST::Identifier.new('add_one'),
+      [AST::Identifier.new('n')],
+      AST::Block.new([
+        AST::Binary.new(
+          AST::Operators::ADD,
+          AST::Identifier.new('n'),
+          AST::Number.new(1.0)
+        )
+      ])
+    ).execute(env)
+
+    AST::FunctionCall.new(
+      AST::Identifier.new('add_one'),
+      [
+        AST::Number.new(5)
+      ]
+    ).execute(env)
+
+    expect do
+      AST::FunctionCall.new(
+        AST::Identifier.new('print'),
+        [
+          AST::Identifier.new('n')
+        ]
+      ).execute(env)
+    end.to raise_error('Undefined variable n')
+  end
 end