Sample application for CB 7.9.0, UPI 1.5.3, Core 5.3.6, PhonePe 1.6.1 and GPay 1.4.0.
Try SampleApp.apk to get a feel of how PayU PG and CB works.
For hash generation testing salt needs to be put in HASH generation method and one set of test creds can be found on gitbook- https://payumobile.gitbook.io/sdk-integration/test-merchant-list