fails:Kernel#instance_variable_get tries to convert the passed argument to a String using #to_str
fails:Kernel#instance_variable_get returns the value of the passed instance variable that is referred to by the conversion result
fails:Kernel#instance_variable_get returns nil when the referred instance variable does not exist
fails:Kernel#instance_variable_get raises a TypeError when the passed argument does not respond to #to_str
fails:Kernel#instance_variable_get raises a TypeError when the passed argument can't be converted to a String
fails:Kernel#instance_variable_get raises a NameError when the conversion result does not start with an '@'
fails:Kernel#instance_variable_get when passed Symbol returns the value of the instance variable that is referred to by the passed Symbol
fails:Kernel#instance_variable_get when passed Symbol raises a NameError when passed :@ as an instance variable name
fails:Kernel#instance_variable_get when passed Symbol raises a NameError when the passed Symbol does not start with an '@'
fails:Kernel#instance_variable_get when passed Symbol raises a NameError when the passed Symbol is an invalid instance variable name
fails:Kernel#instance_variable_get when passed String returns the value of the instance variable that is referred to by the passed String
fails:Kernel#instance_variable_get when passed String raises a NameError when the passed String does not start with an '@'
fails:Kernel#instance_variable_get when passed String raises a NameError when the passed String is an invalid instance variable name
fails:Kernel#instance_variable_get when passed String raises a NameError when passed '@' as an instance variable name
fails:Kernel#instance_variable_get when passed Fixnum raises a TypeError
