+3 failing tests: global scope
+2 test pass: set of attributes on global scope
+1 test pass: set variable from outside, read of variable from code
+2 failing test: variable name different from "a"
+2 test pass: variable name different from "a"
+2 failing test: creation of subscopes
+2 test pass: creation of subscopes
+1 passing test: changing value of parant scope from subscope
+2 failing test: Scope#define_attribute
+2 test pass: Scope#define_attribute