{ "test_expression_literal": {"expression": "foo"}
, "test_read_vars":
  {"vars": ["FOO"], "expression": {"type": "var", "name": "FOO"}}
, "test_call_import":
  { "vars": ["FOO"]
  , "imports": {"read_foo": ["readers", "real_foo_reader"]}
  , "expression": {"type": "CALL_EXPRESSION", "name": "read_foo"}
  }
, "test_overwrite_import":
  { "vars": ["FOO"]
  , "imports": {"read_foo": ["readers", "proxy_foo_reader"]}
  , "expression": {"type": "CALL_EXPRESSION", "name": "read_foo"}
  }
, "test_missing_vars": {"expression": {"type": "var", "name": "FOO"}}
, "test_missing_imports":
  {"expression": {"type": "CALL_EXPRESSION", "name": "read_foo"}}
, "test_malformed_function": "not_an_object"
, "test_malformed_expression": {"missing_expression": {}}
, "test_malformed_vars":
  {"vars": "not_a_list", "expression": {"type": "empty_map"}}
, "test_malformed_imports":
  {"imports": "not_an_object", "expression": {"type": "empty_map"}}
}