[KAFKA-10200] MockProcessorContext doesn't work with WindowStores

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.7.0
• Component/s: streams, streams-test-utils
• Assignee: John Roesler
• Reporter: John Roesler
• Created: 25/Jun/20 17:17
• Updated: 10/Oct/20 03:01
• Resolved: 10/Oct/20 03:01

Description

The recommended pattern for testing custom Processor implementations is to use the test-utils MockProcessorContext. If a Processor implementation needs a store, the store also has to be initialized with the same context. However, the existing (in-memory and persistent) Windowed store implementations perform internal casts that result in class cast exceptions if you attempt to initialize them with the MockProcessorContext.

A workaround is to instead embed the processor in an application and use the TopologyTestDriver instead.

Issue Links

• is duplicated by: KAFKA-8630 Unit testing a streams processor with a WindowStore throws a ClassCastException
• is related to: KAFKA-10215 MockProcessorContext doesn't work with SessionStores
• links to: GitHub Pull Request #8927
• links to: https://github.com/apache/kafka/pull/8927