Flutter Test Coverage | How to Generate & Analyse Report?

In today’s fast-paced world of app development, ensuring the quality of your Flutter application is more critical than ever. With a myriad of devices, screen sizes, and user expectations, developers face the daunting task of crafting apps that are not only functional but also reliable. This is where Flutter test coverage comes into play.

Test coverage is a vital aspect of any software development process, and when it comes to Flutter, it’s no different. In this blog, we will discuss Flutter test coverage, its significance, different techniques, and best practices to achieve high test coverage. Let’s start with Flutter.

Flutter is the most popular cross-platform mobile framework used by developers globally. Statistics show that over 46% of software developers use Flutter. That is, roughly one-third of mobile developers use cross-platform technologies or frameworks.

What is Flutter Test Coverage?

Flutter test coverage refers to the percentage of your Flutter application’s code that is executed by your automated tests or via manual testing. It is a metric that helps you evaluate the quality of your testing efforts by showing how well your tests cover your codebase. 

It is usually expressed in percentage, and a higher percentage indicates better coverage. 

For example, if your Flutter test coverage is 80%, it means that your tests covered 80% of your code. It can help you identify areas of your code that aren’t tested yet, allowing you to focus on those areas.

Note – There are various test coverage techniques to analyze the test coverage metrics.

High test coverage is typically considered good practice in software testing because it helps catch bugs and ensure that your code behaves as expected. However, it’s important to note that high test coverage alone does not guarantee that your application is entirely free of bugs. It’s just one of many factors that helps you maintain code quality.

💡– Learn more about Flutter testing and why testing Flutter applications is crucial. 

There are two ways to test Flutter apps. You can either use Flutter’s built-in testing framework or a low-code test automation platform where you can avoid the hassle of writing code or using Flutter commands.

Pre-Requisite Required to do Flutter Test Coverage

The pre-requisite needed to do Flutter test coverage is quite simple,

• Prepare Flutter test cases. Write precise test cases that cover every test scenario.
• Run these tests. Automate Flutter tests to get high test coverage every time the automated tests are executed.

How Do You Maximize Flutter Test Coverage?

Maximizing test coverage in Flutter involves writing tests that exercise as much of your codebase as possible. Here are some strategies to help you achieve high test coverage in Flutter,

Unit Tests

Unit tests focus on testing individual units of code (For example, functions, methods, or classes) in isolation. You can simply write tests for each function/method to verify that it behaves as expected. Unit testing is usually performed by the developers who built the code. The following pre-requisite is required to perform unit test,

• IDE – Eclipse, Android Studio, or VS code to create Flutter codebase
• Framework – Flutter
• Lcov – test coverage file
• Create unit test cases

You can either manually write test cases or automate Flutter tests using a test automation platform like Testsigma. Also, well-defined test cases can help achieve maximum test coverage.

The above quote by Boris Beizer shows how well-designed test cases could help prevent bugs and create a quality product. And one way to do it is to do comprehensive testing. Learn more about how test case design can help get maximum test coverage.

Widget Tests

Widget testing helps verify the behavior of Flutter widgets and their interactions. Flutter offers in-build test commands to run widget tests. However, this requires high technical skills to create and run Flutter tests. That’s where low-code test automation platforms like Testsigma can help. We will discuss below how low-code automation can help increase test coverage.

Integration Tests

Integration tests verify that different parts of your application work together as expected. You can use Testsigma to automate integration tests without writing any code.

Black Box Tests

You can automate the black box tests of Flutter applications using a black box test automation tool, to maximize the test coverage.

You can automate these tests using various tools and frameworks. Choosing the best tool is the most challenging task. Here, I will explain how Testsigma, an AI-powered automated testing tool, can make Flutter testing a simple and efficient task. 

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Automated Flutter Testing with Testsigma For High Test Coverage

Testsigma is a robust, low-code, cloud-based test automation platform that lets you automate web, mobile, desktop, and API tests in one place. With Testsigma, you can automate Flutter tests as well. 

Also, you can create Flutter tests using NLPs or the record feature (That is, you can interact with the application and run them as automated tests on the cloud).

Let me show you how you can automate Flutter tests without writing any line of code.

Step 1: Log in to the application. Create a new project or use an existing project. To do so, go to Create – New Project.

Step 2: Now, you need to upload the APK file to start creating test cases. You can upload APK files in two ways.

• Go to Test Data – Upload and upload your APK file to create test cases.

• Once you’ve created a project, you will be redirected to create test cases, and when you click on Record, you will prompted to the below screen. You can upload your APK files here, too.

Step 3: Once the APK file is uploaded, you can choose the Test Lab – Testsigma Lab or your local device to create test cases. 

In this instance, I have chosen the Testsigma Lab. Here, I have chosen a device from the list of devices supported. For example, Google Pixel 7.

Also, when you choose your Test Lab as Local Devices, you will be allowed to connect your local device to Testsigma. And, as you interact with the app, Testsigma can run them as automated tests later on the cloud.

Step 4: On clicking Record, your application will load on a mobile device on the cloud, where you can start creating your test cases by using our intuitive interface. 

Step 5: Once the test cases have been created, click on Run to execute tests.

Also, with Testsigma, you can scan and test advanced features, including QR codes, using the Camera image injection feature. When will it be helpful? Suppose your application has a QR code, and you want to test if users are able to scan and do permitted actions. That’s when this feature will help.

Here are some of the benefits of automating Flutter testing with Testsigma,

Scriptless Test Automation: Testsigma allows you to create and manage tests without writing any code. This makes testing accessible for both technical and non-technical teams.

Cross-Browser Testing: Testsigma supports testing across multiple browsers, platforms, versions, and devices, ensuring that your Flutter application works consistently across different environments. This is especially crucial for Flutter because it is a cross-platform framework.

Parallel Testing: You can execute tests in parallel, significantly reducing the overall test execution time.

AI-Powered Testing: Testsigma uses AI to help identify elements on the screen, making it easier to create and maintain tests, even as the application evolves.

Third-party Integrations: Testsigma can integrate with popular CI/CD, product management, collaboration, and bug-tracking tools, allowing you to incorporate automated testing into your development workflow seamlessly.

Best Practices to Maximize Flutter Test Coverage

Here are some of the best practices to maximize Flutter test coverage,

• Regularly review and update your tests as your application evolves.
• Make sure to cover edge cases and boundary conditions in your tests. This includes testing for valid and invalid inputs as well.
• As your codebase evolves, make sure to update your tests to reflect any changes in behavior or functionality.
• Integrate tests into your DevOps and CI/CD pipeline.
• Perform thorough unit tests to ensure the code works as expected. This will help catch bugs, if any, in the early stages and can be fixed to avoid serious damage in the later stages.
• Use automated testing tools to get high test coverage as it helps streamline the testing process and reduce manual testing efforts.

By combining a mix of unit tests, widget tests, and integration tests, along with automation tools like Testsigma, you can achieve high test coverage for your Flutter applications.

Flutter Test Coverage Command

Once the developer completes writing unit tests, they can check the code coverage locally using the below Flutter code test coverage command,

Here’s a breakdown of the Flutter command,

• flutter test: This command is used to run Flutter unit tests.
• –coverage: This is used to generate a code coverage report. When you include this option in the Flutter test command, Flutter collects information about the parts of your code that are executed during the tests.

After running the tests with –coverage, it generates a Flutter test coverage report, typically in the coverage/lcov-report directory. This Flutter unit test coverage report can be opened in a web browser to visualize the coverage details.

Take a look at the snippet to understand how the Flutter unit test coverage command works,

This is how the Flutter test coverage report will look like when opened in a web browser.

Flutter Test Coverage Extension

After installing the Flutter Coverage extension, it will be available in your testing tab, providing the coverage information for all files and folders. Also, you will see three different icons indicating areas of your code that require further testing,

• ✅ more than 70% coverage
• ⚠️ between 50% – 70% coverage
• ❌ less than 50% coverage

An alternate way to perform Flutter testing is to use a test automation platform like Testsigma, where testers can easily automate mobile app testing along with web, desktop, and API tests in one platform. Also, by automating tests, testers can focus on other critical tasks, such as exploratory testing. 

Automate your black box tests for flutter apps, 5x faster, with Testsigma

How Testsigma Can Increase Your Flutter Test Coverage?

Low-code test automation is a valuable way to increase test coverage in Flutter app development. Here’s how low-code test automation can increase the Flutter test coverage

• Low-code test automation platforms allow testers to create automated tests using NLPs, record-and-play features, etc. It accelerates the test creation, allowing testers to cover more test scenarios in less time.
• Also, low-code platforms do not require much coding skills, which makes Flutter testing accessible to both technical and non-technical users. It expands the pool of individuals who can contribute to testing efforts.
• Testsigma,  a low-code test automation tool, supports over 3000+ real devices/tablets and 1000+ browser/OS combo. This means that you can easily create tests that cover multiple OS, browsers, versions, and devices, increasing the scope of your test coverage.
• Parallel testing is another benefit. Parallel test execution allows you to run multiple tests simultaneously. This significantly speeds up the testing process, enabling you to cover more ground in less time.
• Makes your Flutter testing 5x faster and ship products at a 10x faster rate. So, you can save time, resources, and efforts. This way, you can test and cover more codebase.

Conclusion

Achieving 100% test coverage may not always be feasible or necessary, but striving for a high level of coverage is essential for building reliable and resilient applications. It’s a crucial part of the development process that pays off in the long run, saving time and resources in debugging and maintenance.

As discussed above, automated testing tools can help you achieve higher test coverage. Automation helps you save time, resources, and effort. Sign up to Testsigma and start automating your tests in less than 2 minutes.

Frequently Asked Questions

How can the code coverage data from Flutter tests be displayed?

You can view the code coverage data from Flutter tests using the following steps,

1. Install lcov in Mac
2. Run tests, generate coverage files, and convert to HTML
3. Open coverage report in the browser

What are the three types of testing supported by Flutter?

The three types of testing supported by Flutter,

• Unit tests
• Widget tests
• Integration tests

What is the purpose of test coverage?

Increasing test coverage means creating more test cases, resulting in fewer defects and less work in later stages, ultimately leading to higher customer satisfaction with a better product.

What is flutter test coverage vs code?

The difference between code coverage and test coverage is simple. Flutter test coverage refers to the extent to which a set of tests covers the codebase of a program. In contrast, code coverage refers to the percentage of code that has been executed by the test suite.