read / write
The default context that a Query runs on.
For classes that require a ManagedContext - like Query - this is the default context when none is specified.
This value is set when a ManagedContext is instantiated in an isolate; the last context created is the default context. Most applications will not use more than one ManagedContext. When running tests, you should set this value each time you instantiate a ManagedContext to ensure that a previous test isolate state did not set this property.