Integration tests with TangoEventTracer

The module ska_tango_testing.integration provides a set of tools to write integration tests for Tango devices using an event-driven approach. Essentially this module gives you a relatively simple and well tested code to capture events from Tango devices and then make assertions on them, without the need to re-write the subscribe_event logic or to rely to while ... sleep loops to wait for events.

Advantages and differences with other tools

Compared to the other tools that this library offers, like “event recorders” or ska_tango_testing.mock, this module’s tools provide a more simplified, concise and high-level way to capture and assert events especially useful for integration tests where mocks are not needed. If you are looking for a more low-level and flexible approach to test asynchronous behaviours, you may want to look at the ska_tango_testing.mock module. If instead you are writing integration tests and you need to verify from outside that an SUT produces certain change events, then ska_tango_testing.integration probably is the right choice.

Being encapsulated in a library this tool has also the advantage of being already unit tested and potentially shared among different projects, without code duplication.

Module content overview

The central tool provided by the module is TangoEventTracer, which is a class that can be used to subscribe to device attributes change events, store them locally and then make assertions over them using the library assertpy and some additional custom assertions provided by the module itself (see assertions).

This module provides also some additional event live-logging utilities, to help you debugging your tests.

To begin using ska_tango_testing.integration we recommend starting with the Getting started with TangoEventTracer guide, to learn about TangoEventTracer and how it can be used to capture events and make assertions. Then, we recommend to read Advanced Use Cases for the Assertions to learn about the full set of features of the tracer and the assertions. If you are looking for more technical use-cases and examples, you can refer to the Custom queries and assertions using TangoEventTracer guide and finally to the API reference.

Integration tests with TangoEventTracer

• Getting started with TangoEventTracer
  • Basic usage
  • Quick explanation of the assertion
  • Two notes on the usage of assertions
  • Error messages and debugging
  • Typed events
  • Logging
• Advanced Use Cases for the Assertions
  • Minimum number of Events (min_n_events)
  • Custom predicate (custom_matcher)
  • Early Stop Sentinel (with_early_stop)
  • Timeout as an object (ChainedAssertionsTimeout class)
• Custom queries and assertions using TangoEventTracer
  • Interacting with the tracer
  • Interaction through the predicate shortcut
  • Interaction through queries
  • Custom assertions
• Event logger