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Maestro is an open-source mobile and web UI testing framework designed for end-to-end automation. It aims to make automating end-to-end testing on iOS and Android easier than ever, and now also supports web applications. The tool has gained attention for its simplicity and user-friendly approach, making it accessible for both experienced and beginner developers or QA engineers.

Key Features of Maestro

Maestro is built on lessons learned from its predecessors, such as Appium, Espresso, UIAutomator, XCTest, Selenium, and Playwright. Its core features include:

  • Cross-Platform Support: Maestro supports testing on both Android and iOS applications, including native views, Jetpack Compose, UIKit, SwiftUI, React Native, Flutter, and .NET MAUI. It also extends its capabilities to web views and desktop browsers, allowing tests to be written once and run across platforms with minimal adjustments.
  • Built-in Tolerance to Flakiness and Delays: A significant challenge in mobile testing is stability. Maestro addresses this by embracing the instability of mobile applications and devices, incorporating features that counter flakiness. It automatically waits for content to load, eliminating the need for manual sleep() or wait() calls, which can otherwise add unnecessary lag to test execution.
  • Readability and Maintainability (YAML Syntax): Maestro tests are defined in YAML files, which are highly human-readable. This declarative syntax makes it easier for new team members to understand and maintain existing tests, as it doesn’t require a deep understanding of programming knowledge.
  • Simple Setup: Maestro is designed for quick installation and setup, often allowing users to begin writing and executing tests within minutes. It operates as a single binary.
  • Fast Iteration: Tests are interpreted, meaning there’s no compilation needed. Maestro can continuously monitor test files and rerun them as changes occur, enabling rapid iteration.

Installation and Setup

Installing Maestro is generally straightforward. For macOS and Linux, a simple curl command downloads and sets up the necessary files. For iOS testing, an additional tool called idb from Facebook (Meta) is required to connect to the simulator. While possible on Windows, it can be “a bit hard to set it up” and may require installing Linux on top and linking ADB.

A notable advantage of Maestro is that it operates as a “black box” testing tool. You do not need to add any plugins, dependencies, or modify your application’s gradle configuration or source code to use Maestro. It works by interacting with the application as installed on an emulator, simulator, or physical device.

Writing Maestro Tests (Flows)

Maestro tests are organized into “flows,” which represent parts of a user journey within an app, such as login or checkout. These flows are written in YAML files.

  • Basic Structure: A flow file starts by specifying the appId of the application to be tested. For web testing, a url is specified instead.
  • Commands: Maestro provides a variety of commands for simulating user interactions. Some common commands include:
    • launchApp: Launches the application. It’s recommended to use clearState with this command to ensure each test is isolated by clearing cached data and storage.
    • tapOn: Taps on an element, which can be identified by its text, ID, or regular expression.
    • inputText: Inputs text into a field.
    • assertVisible: Verifies that a specific element or text is visible on the screen.
    • runFlow: Allows nesting of flow files, promoting modularity and reusability. For example, a common login flow can be written once and reused across many test cases.
    • waitForAnimationToEnd and extendedWaitUntil: These intelligent wait commands help in making tests more robust, pausing the flow until screen movement stops or a referenced element appears in the hierarchy, especially useful in animation-heavy apps or when dealing with network and UI render performance variations.
    • back: Simulates pressing the back button.
    • scroll: Enables scrolling on the screen.
  • Selectors: While Maestro allows tapping based on a point selector (coordinates), it’s strongly advised to avoid using the point selector. Point selectors are prone to breaking with different viewport sizes and can interfere with Maestro’s underlying logic for waiting on elements. Instead, using text or id selectors is recommended for improved stability.
  • Accessibility and Test Stability: For better accessibility and cross-platform compatibility, it’s often preferred to identify elements by text rather than id. Relying on text can help identify and resolve accessibility issues within the application itself.
  • Handling Permissions: Maestro automatically handles permission dialogues by default, accepting all permissions. However, this behavior can be configured if specific permission flows need to be tested.
  • Authentication Flows: For applications with multi-factor authentication (e.g., OTP), custom solutions (like backend endpoints to retrieve OTPs) might be needed to bypass these steps in automated tests.

Maestro Studio

Maestro Studio is a built-in IDE-like tool that significantly simplifies the creation, editing, and validation of Maestro tests.

  • It launches a local web server, allowing users to visually interact with their emulator, simulator, or web application through a browser interface.
  • Users can click on elements on the screen to generate suggested Maestro commands (like tapOn, assertVisible) and even execute them directly to see the effect.
  • The studio can also record user interactions, which can then be exported as a flow file, streamlining the process of writing regression tests. This “what you see is what you get” approach makes test creation intuitive.

Maestro Cloud and CI Integration

Maestro offers a cloud platform for executing tests, which addresses common issues like environment alignment and scalability.

  • Environment Alignment: A significant contributor to test instability is the difference between local development environments and cloud test environments (e.g., emulator images, memory, network, firmware). Moropo (a mobile testing blog) highlights that using a tool like Moropo Test Creator to build Maestro tests directly in the same cloud environment where they are executed during CI vastly reduces validation and stabilization time.
  • Scalability and CI/CD: Maestro Cloud allows tests to be run remotely and in parallel, and integrates well with CI/CD pipelines, including GitHub Actions. This enables teams to avoid bottlenecks associated with bespoke local setups.
  • Debugging and Reporting: Maestro Cloud provides recordings of test runs, showing the current step being executed, which is helpful for debugging failed tests. It also supports generating HTML and XML (JUnit) reports of test execution results. Video recordings of test execution are also available, with a previously noted limit of two minutes, though this has reportedly been increased.
  • Cost: Maestro Cloud offers a pay-as-you-go model, typically costing about 10 cents USD per test flow run. For organizations, this can be a very cost-effective solution for running regression tests. Free credits are often provided for initial exploration.

Comparison to Other Tools

Maestro is frequently compared to other mobile testing frameworks:

  • Appium: Maestro is described as simpler to install and use than Appium, which is a lower-level framework based on a server process. While Appium allows for greater flexibility with various programming languages and the creation of complex test frameworks (e.g., with Webdriver.io, Codecept, or Robotframework), Maestro is keyword-driven (YAML) and has a more defined set of keywords, offering less flexibility for custom definitions or complex control structures. Appium is seen as preferred for strong, scalable automation test suites, especially for larger teams who need to write proper test frameworks with less repetitive code. However, Appium has been noted to have flakiness issues.
  • Espresso/XCTest/UIAutomator: Maestro is built on learnings from these native frameworks and offers built-in flakiness and delay tolerance, which often requires manual configuration (like disabling animations) in Espresso.
  • Detox: Mentioned as an alternative that offers similar benefits to Appium in terms of framework capabilities but has overcome many flakiness issues. However, it primarily works with React Native apps.

Advantages and Benefits

  • Ease of Use: Maestro’s simple installation, declarative YAML syntax, and the visual assistance provided by Maestro Studio make it very easy to learn and use, even for individuals without deep programming or platform-specific knowledge.
  • Reduced Manual Testing: It effectively optimizes and can replace time-consuming manual regression testing processes, especially for applications with many critical paths or frequent releases.
  • Improved Application Quality: By making it easy to write regression tests, Maestro helps identify and improve issues related to accessibility and design systems, leading to a better user experience.
  • Community and Open Source: Maestro is an open-source project with an active community on platforms like Slack and GitHub. Users can contribute, report issues, and request features, fostering continuous improvement.

Limitations and Considerations

While powerful, Maestro does have some considerations:

  • Windows Installation Complexity: As discussed, setting up Maestro on Windows can be more involved than on other operating systems.
  • Selector Limitations: The point selector is unreliable and should be avoided. While id is useful, relying solely on it can hinder cross-platform testing and accessibility, emphasizing the need for text or accessibility labels.
  • Custom Keyword/Looping: Maestro has a defined set of keywords and limited control structures, which might require using JavaScript snippets for more flexibility. While looping commands exist, specific complex looping scenarios might need community input.
  • Device Configuration in Cloud: The cloud environment currently offers limited device configuration options (e.g., primarily API version of the OS).

Conclusion

Maestro presents itself as a painless and effective solution for end-to-end UI automation testing across mobile and web platforms. Its focus on simplicity, built-in flakiness tolerance, and user-friendly tools like Maestro Studio make it a strong contender for teams looking to quickly implement and scale their testing efforts, especially those aiming to reduce manual testing overhead and improve application quality. While it may have some limitations compared to lower-level frameworks for highly complex, customized testing needs, its overall ease of adoption and robust features make it a highly recommended tool.