What is serialization and deserialization in API test automation?

Answer

Serialization and Deserialization in API Testing

In the context of API testing, these terms refer to converting Java objects into JSON (or XML) format and vice versa. This is essential when sending and receiving data to and from APIs, as most APIs use JSON or XML as their data format.

Serialization

▸Converting a Java object → JSON string (for sending in the request body)

Deserialization

▸Converting a JSON string → Java object (for reading and asserting the response)

Example Scenario

Consider an API with these endpoints:

✓POST /api/person — create a new person
✓GET /api/person/{id} — retrieve a person''s details

Step 1: Create POJO Class

Java

public class Person {
    private String name;
    private int age;

    public Person() { }

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Getters and Setters
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public int getAge() { return age; }
    public void setAge(int age) { this.age = age; }
}

Step 2: POST Request with Serialization

Java

public class ApiTest {

    @BeforeClass
    public void setup() {
        RestAssured.baseURI = "http://example.com/api";
    }

    @Test
    public void testCreatePerson() {
        Person person = new Person("John Doe", 30);

        Response response = given()
                                .contentType(ContentType.JSON)
                                .body(person)  // ← Serialization happens here
                                .when()
                                .post("/person");

        assertEquals(response.getStatusCode(), 201);
    }
}

In testCreatePerson, the Person object is converted into a JSON string using the Jackson library (handled internally by REST Assured) when passed to .body().

Step 3: GET Request with Deserialization

Java

    @Test
    public void testGetPerson() {
        Response response = given()
                                .when()
                                .get("/person/1");

        assertEquals(response.getStatusCode(), 200);

        Person person = response.as(Person.class);  // ← Deserialization happens here

        assertEquals(person.getName(), "John Doe");
        assertEquals(person.getAge(), 30);
    }

In testGetPerson, the JSON response is converted back into a Person object using .as(Person.class).

Jackson Library Requirement

Add to pom.xml:

XML

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.15.0</version>
</dependency>