Explain what is meant by specification in the context of REST Assured and how it is used in API testing.

In the context of REST Assured, a specification is a predefined set of configurations and parameters for HTTP requests and response validations that can be reused in tests. The specification includes the base URL, headers, parameters, as well as expected response codes and schemas.

Applying a specification allows standardizing and simplifying API test writing, avoiding code duplication. For example, you can create a specification with common settings for all requests to a certain service and then use it in different tests.

Example in Java:

import static io.restassured.RestAssured.*;
import io.restassured.builder.RequestSpecBuilder;
import io.restassured.specification.RequestSpecification;

RequestSpecification spec = new RequestSpecBuilder()
    .setBaseUri("https://api.example.com")
    .addHeader("Authorization", "Bearer token")
    .build();

given()
    .spec(spec)
.when()
    .get("/users")
.then()
    .statusCode(200);

Thus, a specification helps centrally manage request settings and improves the readability and maintainability of tests.