In Spring Boot, to perform integration testing and enable full application context loading, you use the @SpringBootTest annotation. This annotation loads the entire Spring application context, making it suitable for integration testing scenarios.

To customize the response body of a global exception handler method in Spring Boot, the method should return an object of type ResponseEntity. This allows you to create a custom response with specific status codes, headers, and response bodies when an exception is caught globally. It provides flexibility in crafting error responses tailored to your application's needs.

Optimizing a Spring Boot application for faster startup times involves strategies like minimizing the number of auto-configured beans, using lazy initialization for non-essential components, and optimizing classpath scanning. These approaches reduce the initial overhead and improve startup times. The other options, such as increasing auto-configured beans or increasing thread pool size without consideration, can lead to performance issues or longer startup times.

In Spring Boot, you can define hierarchical properties in a YAML configuration file using YAML nesting. YAML allows you to structure your configuration data hierarchically, making it easy to organize and manage complex configuration settings for your application. This helps in maintaining a clean and readable configuration.

The primary purpose of using TestContainers in Spring Boot is to create lightweight, isolated Docker containers for testing. This allows you to run tests in an environment that closely resembles your production environment and is especially useful for testing database interactions.

To optimize the performance of RESTful APIs in Spring Boot, developers can enable GZIP compression for the HTTP response. Enabling GZIP compression reduces the amount of data sent over the network by compressing the response before sending it to the client. This reduces the bandwidth usage and speeds up API response times, especially when dealing with large payloads. Enabling GZIP compression is a common technique for improving the performance of web applications, including RESTful APIs.

In a Spring Cloud environment, to configure a service to discover its peers using Eureka, the property eureka.client.register-with-eureka must be defined in the application's properties or YAML file. This property determines whether the service should register itself with the Eureka server. Setting it to true allows the service to register, and it will be discoverable by other services through Eureka.

Mockito is a popular framework used for mocking objects in unit tests in Spring Boot applications. It allows you to create mock objects and define their behavior during testing.

In unit testing of Spring Boot applications, the assertTrue method of the Assert class is commonly used to check if the specified condition is true. This is helpful for verifying that a certain condition or assertion holds true during the test.

The primary Spring Cloud component used for service discovery in a microservices architecture is Eureka. Eureka is a server-based service registry that allows microservices to register themselves and discover other services in the system.