Mailosaur Getting Started

If you want to create end-to-end tests that rely on email verification such as sent, confirmation, password reset, etc. Mailosaur is your friend. Note: You will need a Mailosaur account to create a new trial account; sign up here. In this technical post, we will go over the required configuration to set up an email sent validation. Let’s start by creating a new Gradle - Java project with Kotlin DSL script :) build.gradle.kts should look like this:

plugins {

val mailosaurVersion: String by project
val junitJupiterVersion: String by project

group = "com.josdem.mailosaur"
version = "1.0-SNAPSHOT"

repositories {

dependencies {

tasks.getByName<Test>("test") {
    systemProperty("mailosaurApiKey", System.getProperty("mailosaurApiKey"))
    systemProperty("mailosaurServerId", System.getProperty("mailosaurServerId"))

This is a cool approach using gradle.properties to define version values and refer those in the DSL script. Also we are reading the API key and server ID required to authenticate to Mailosaur, you can see all this data at the Mailosaur Dashboard. Now create a Junit5 test case to validate an email in your inbox.

package com.josdem.mailosaur;

import com.mailosaur.MailosaurClient;
import com.mailosaur.MailosaurException;
import com.mailosaur.models.Message;
import com.mailosaur.models.MessageSearchParams;
import com.mailosaur.models.SearchCriteria;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

import java.io.IOException;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;

class MailosaurSenderTest {

    private static final String SERVER_DOMAIN = ".mailosaur.net";

    private String apiKey = "YOUR_API_KEY";
    private String serverId = "SERVER_ID";

    void setup() {
        serverId = System.getProperty("mailosaurServerId");
        apiKey = System.getProperty("mailosaurApiKey");

    @DisplayName("Sending email")
    void shouldSendEmail() throws MailosaurException, IOException {
        MailosaurClient mailosaur = new MailosaurClient(apiKey);
        MessageSearchParams params = new MessageSearchParams();

        SearchCriteria criteria = new SearchCriteria();
        criteria.withSentTo("josdem@" + serverId + SERVER_DOMAIN);
        Message message = mailosaur.messages().get(params, criteria);

        assertNotNull(message, "we should have a message");
        assertEquals("test", message.subject(), "email subject should be test");

Please notice how we are reading mailosaurServerId and mailosaurApiKey from system properties, how cool is that?. To run the project:

gradle test -DmailosaurApiKey=${mailosaurApiKey} -DmailosaurServerId=${mailosaurServerId}


 - ${mailosaurApiKey} Is the Mailosaur API Key
 - ${mailosaurServerId} Is the Mailosaur Server Id

To browse the code go here, to download the code:

git clone git@github.com:josdem/mailosaur-workshop.git

Return to the main article

comments powered by Disqus