API Testing with Java + RestAssured + TestNG + Truth

APIClient.java

package org.example.services;

import io.restassured.RestAssured;
import java.util.List;

public class APIClient<T> {
    private final Class<T> type;
    private final String baseUrl;
    private final String endpoint;

    private final String CONTENT_TYPE = "application/json";

    public APIClient(Class<T> type, String endpoint) {
        this.type = type;
        this.baseUrl = "https://jsonplaceholder.typicode.com";
        this.endpoint = endpoint;
    }

    public List<T> getAll() {
        return RestAssured
                .get( baseUrl + endpoint)
                .getBody()
                .jsonPath()
                .getList(".", type);
    }

    public T create(T todo) {
        return RestAssured
                .given()
                .contentType(CONTENT_TYPE)
                .body(todo)
                .post(baseUrl + endpoint)
                .getBody()
                .jsonPath()
                .getObject(".", type);
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>java-test-api</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>22</maven.compiler.source>
        <maven.compiler.target>22</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>7.9.0</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>io.rest-assured</groupId>
            <artifactId>rest-assured</artifactId>
            <version>5.4.0</version>
            <scope>compile</scope>
        </dependency>

        <dependency>
            <groupId>com.google.truth</groupId>
            <artifactId>truth</artifactId>
            <version>1.4.2</version>
            <scope>test</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.10.1</version>
        </dependency>

    </dependencies>

</project>

Todo.java

package org.example.models;

public class Todo {
    private int id;
    private int userId;
    private String title;
    private boolean completed;

    public Todo(int id, int userId, String title) {
        this.id = id;
        this.userId = userId;
        this.title = title;
        this.completed = false;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public boolean isCompleted() {
        return completed;
    }

    public void setCompleted(boolean completed) {
        this.completed = completed;
    }

    @Override
    public String toString() {
        return STR."Todo{id=\{id}, userId=\{userId}, title='\{title}\{'\''}, completed=\{completed}\{'}'}";
    }
}

TodoService.java

package org.example.services;

import org.example.models.Todo;
import java.util.List;

public class TodoService {
    private final APIClient<Todo> client;

    public TodoService() {
        this.client = new APIClient<>(Todo.class, "/todos");
    }

    public List<Todo> getAll() {
        return client.getAll();
    }

    public Todo create(Todo todo) {
        return client.create(todo);
    }
}

TodoTests.java

import org.example.models.Todo;
import org.example.services.TodoService;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;

import static com.google.common.truth.Truth.assertThat;

public class TodoTests {
    private TodoService service;

    @BeforeClass
    public void setUp() {
        service = new TodoService();
    }

    @Test
    public void getAll_ReturnsTodos() {
        var todos = service.getAll();

        assertThat(todos).isNotEmpty();
    }

    @Test
    public void create_SampleTodo_ReturnsStatusCreated() {
        var todo = new Todo(0, 1, "Titulito");
        var newTodo = service.create(todo);

        assertThat(newTodo).isNotNull();
    }
}