Automated software-testing systems and computer program products use mock software entities to perform integration testing on a microservices-based application. The mock entities emulate the behavior of other microservices or external software applications that would normally interact with the tested microservices in a production environment. The mock entities are managed by a mock server that communicates with the test system through a messaging system. The mock server determines how the mock entities should respond to the tested application's service requests by referring to test guidelines stored in a behavior store. During testing, the test system dynamically updates the behavior store in response to the tested application's service requests and to other indicators of the current state of the tested application. If the tested application interacts with the mock entities during the test as expected, the test system deems the application to have passed the integration test.