The TestRestTemplate utility is primarily used for performing HTTP requests in integration tests in Spring Boot applications. It provides a simple and convenient way to send HTTP requests and receive responses in your tests.

To ensure correct handling of interactions with external services, you would use mock objects or libraries like WireMock to simulate the responses of external services. This approach allows you to control the behavior of the external services during testing without actually making real requests. Live testing against real external services is not recommended in automated testing as it introduces dependencies and can be unreliable. Skipping testing interactions or relying solely on documentation is not a robust testing strategy.

In Spring Cloud, Ribbon is a client-side load balancer that dynamically routes client requests to multiple instances of a service. This helps distribute the load evenly and provides fault tolerance by automatically rerouting requests if a service instance fails.

In JUnit, the @BeforeEach annotation is used to execute a method before each test method in the test class. This is often used for setup operations required before each test case.

To optimize the performance of a Spring Boot application, developers can use "Actuator" to profile and monitor the application in real-time. Spring Boot Actuator provides various production-ready features, including endpoints for monitoring and managing the application. These endpoints can be used to gather metrics, health information, and other runtime data, helping developers identify and address performance issues.

The @EnableAutoConfiguration annotation enables Auto Configuration in a Spring Boot application. It triggers the automatic configuration of beans and components based on the project's dependencies and classpath. @SpringBootApplication is a meta-annotation that includes @EnableAutoConfiguration along with other annotations. @Configuration is used to define Java-based Spring configurations, and @ComponentScan is used for component scanning. They are not directly related to enabling Auto Configuration.

Option 1 is correct. Profiling tools like VisualVM can capture and analyze thread dumps, helping identify performance bottlenecks by showing which threads are causing delays. Increasing heap size or disabling logging may not directly address the root cause of high latency. Adding more physical memory could help with memory-related issues but may not solve latency problems.

In Mockito, you can use the verify method to ensure that a mocked method was called with specific arguments. This is helpful for verifying that your code under test interacts with the mocked dependencies as expected.

Ribbon is a client-side load balancing library used in microservices-based applications. It contributes to the functioning by balancing the traffic between multiple instances of a service, making the application more resilient and efficient. Ribbon helps in handling inter-service communication by distributing requests effectively.

Spring Cloud Config is the component that simplifies the deployment of microservices by providing solutions to common patterns in distributed systems, such as externalized configuration management.