When running test classes in a Spring Boot application with WebSocket integration, you may encounter the error:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'serverEndpointExporter' 
Invocation of init method failed; nested exception is java.lang.IllegalStateException: 
javax.websocket.server.ServerContainer not available

This occurs because WebSocket funcsionality requires a servlet container, which isn't automatically initialized in test contexts by default. The solution is to explicitly configure the test environment:

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class WebSocketTest {
    // Test methods
}

Key configuration options for webEnvironment:

• RANDOM_PORT: Starts an embedded server on a random port
• DEFINED_PORT: Uses a defined port (from application.properties)
• MOCK: Creates a mock servlet environment
• NONE: Doesn't start any web environment

For WebSocket testing, either RANDOM_PORT or DEFINED_PORT must be used to ensure the servlet container is available. The random port approach is generally preferred to avoid port conflicts during testing.