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Simulating a control system
For testing, it can be useful to simulate a control system.
This has various benefits:
- It allows one to test without access to a running control system.
- It allows one to test extreme states of the control system.
- It allows one to test setting values that one would not want to in a control system.
The control system simulation consists of:
- A component run within the browser that provides updates to process variables
- A DSL that defines those process variables that should be simulates
- A DSL that defines how process variables should be updated.
- A mechanism whereby these DSLs can be specified.
The types that are used in the cs-web-proto repo are VTypes, which are an implementation of EPICS normative types (see the wiki page). This implementation is copied from Java: part of the epicsCoreJava repo here.
When a component requests a PV with a prefix sim:// and a suffix which is understood, periodic updates should started that are dispatched to the store via the plugin interface.
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sim://sine: a double value that oscillates about zero -
sim://disconnector: a random double value that occasionally disconnects -
sim://readonly: a random double value that has readonly set to true (actually all the sim PVs should be readonly really so perhaps this is not necessary) -
sim://sinewave: a double array that shows a sinewave moving over time -
sim://alarm: a double value that has an alarm state that changes at random
There is similarly a use for 'local' PVs with a loc:// prefix. These are different but could also be supported. They cache a value supplied by the UI and update the store when it changes.
These are supported by CS-Studio and Phoebus so we have an existing definition to work with.
Epics 7 provides a process variable introspection interface it might make sense to copy this.
This simulation might be useful for functional testing.
One could imagine quite complicated interactions with a control system (mocking the interaction with the control system). One could imagine mocking this value out.