1. A testbed for testing health of avionics software, the testbed comprising a memory and a program stored in the memory and configured to be executed by a processor, the program comprising; an input model representing an input system for the avionics software, the input model providing inputs from external systems; a hardware model representing one or more avionics hardware components on which the avionics software runs; a resource modeler coupled to the input model and the hardware model, the resource modeler configured to estimate effects on the avionics software of conditions of the avionics hardware components, other software modules other than the avionics software, or both; one or more interdependency models coupled to the input model and the resource modeler, the interdependency models including information relating to one or more relationships between the avionics software and the hardware that are not modeled in the hardware model and that are utilized by the resource modeler to introduce effects due to faults in the one or more avionics hardware components and to study effects of the faults on the avionics software; a fault injector configured to simulate one or more faults in one or more of the hardware, the other software modules, or the inputs; a disturbance model coupled to the fault injector and the resource modeler, the disturbance model including information relating to a relationship between the one or more faults and the avionics software that is utilized by the resource modeler in estimating the effects on the avionics software of the one or more faults; a plurality of sensor models configured to detect conditions of the hardware; and a plurality of monitors configured to detect conditions of the avionics software; wherein the resource modeler is coupled to the plurality of sensors and the plurality of monitors and is configured to estimate the effects on the avionics software using the conditions of the hardware and the conditions of the avionics software.