pass test_creating_hashes
pass test_hash_literals
pass test_accessing_hashes
pass test_accessing_hashes_with_fetch and add comment
pass test_changing_hashes and add comment
pass test_hash_is_unordered
pass test_hash_keys
extend the comment in test_hash_keys
pass test_hash_values
pass test_combining_hashes
pass test_default_value
pass test_default_value_is_the_same_object
pass test_default_value_with_block and finish about_hashes
pass first two tests in about_strings
pass test_use_single_quotes_to_create_string_with_double_quotes
pass next two tests
pass test_use_flexible_quoting_to_handle_really_hard_cases
pass test_flexible_quotes_can_handle_multiple_lines
pass test_here_documents_can_also_handle_multiple_lines
pass test where strings are concatenated