Hands-On Reactive Programming with Reactor

Validating backpressure

As discussed previously in Chapter 7, Flow Control and Backpressure, backpressure allows a subscriber to control event flow. This mechanism is aimed at controlling a fast generating producer. There are different configurations for backpressure. These configurations have already been discussed in Chapter 7, Flow Control and Backpressure, and we will not cover them here. Fundamentally, backpressure skips delivering values to the Subscriber. Consequently, validating it means that we must look for values that have not been delivered to the Subscriber. Reactor provides the verifyThenAssertThat API  for the same reason. This method exposes assertions that can validate the end state of a publisher. Let's now work with a test ...