Java

import java.net.URI;
import java.net.http.*;
import java.time.Duration;
import java.util.regex.*;
import com.fasterxml.jackson.databind.*;

public class TempInbox {
    private static final String BASE = "https://tempinbox.dev";
    private static final HttpClient http = HttpClient.newHttpClient();
    private static final ObjectMapper json = new ObjectMapper();

    public record Inbox(String address, String jwt) {}
    public record Mail(String uuid, String subject, String raw) {}

    public static Inbox createInbox() throws Exception {
        var req = HttpRequest.newBuilder(URI.create(BASE + "/api/new_address"))
            .header("Content-Type", "application/json")
            .POST(HttpRequest.BodyPublishers.ofString("{}"))
            .build();
        var node = json.readTree(http.send(req, HttpResponse.BodyHandlers.ofString()).body());
        return new Inbox(node.get("address").asText(), node.get("jwt").asText());
    }

    public static Mail waitForMail(String jwt, Duration timeout) throws Exception {
        long deadline = System.nanoTime() + timeout.toNanos();
        while (System.nanoTime() < deadline) {
            var list = json.readTree(get("/api/mails?limit=1&offset=0", jwt));
            if (list.get("results").size() > 0) {
                String uuid = list.get("results").get(0).get("uuid").asText();
                var full = json.readTree(get("/api/mail/" + uuid, jwt));
                var meta = json.readTree(full.get("metadata").asText(""));
                return new Mail(uuid,
                    meta.path("subject").asText(""),
                    full.path("raw").asText(""));
            }
            Thread.sleep(2500);
        }
        throw new IllegalStateException("No email received within " + timeout);
    }

    public static String extractOtp(String raw) {
        Matcher m = Pattern.compile("\\b\\d{6}\\b").matcher(raw);
        if (!m.find()) throw new IllegalStateException("No 6-digit OTP found");
        return m.group();
    }

    private static String get(String path, String jwt) throws Exception {
        var req = HttpRequest.newBuilder(URI.create(BASE + path))
            .header("Authorization", "Bearer " + jwt)
            .GET().build();
        return http.send(req, HttpResponse.BodyHandlers.ofString()).body();
    }
}

import org.junit.jupiter.api.*;
import org.openqa.selenium.*;
import org.openqa.selenium.chrome.ChromeDriver;
import java.time.Duration;

class SignupTest {
    WebDriver driver;

    @BeforeEach void setup() { driver = new ChromeDriver(); }
    @AfterEach void teardown() { driver.quit(); }

    @Test void signupWithOtp() throws Exception {
        var inbox = TempInbox.createInbox();

        driver.get("https://your-app.example.com/signup");
        driver.findElement(By.name("email")).sendKeys(inbox.address());
        driver.findElement(By.name("password")).sendKeys("Test1234!");
        driver.findElement(By.cssSelector("button[type=submit]")).click();

        var mail = TempInbox.waitForMail(inbox.jwt(), Duration.ofSeconds(30));
        String otp = TempInbox.extractOtp(mail.raw());

        driver.findElement(By.name("otp")).sendKeys(otp);
        driver.findElement(By.cssSelector("button[type=submit]")).click();

        Assertions.assertTrue(driver.getCurrentUrl().contains("/dashboard"));
    }
}