Flutter Unit Testing For Beginners

Small portions of code are checked individually as part of the automated testing process known as unit testing.

Muhammad Amin

Flutter Developer

What is Unit Testing?

Smaller pieces of code are verified for reliability as part of the automated testing process known as unit testing.
A unit might be a variable, class, state, method, or even just a function.

The test suite’s bottom layer is unit testing.
We test each feature’s internal functionality in this tier.

The following are the main justifications for unit testing in software engineering:


Developers create a portion of code to test a particular function in a software program as part of unit testing.
In order to test this function more thoroughly, developers can isolate it. This will identify any unneeded dependencies between the function under test and other units, allowing for their elimination.
Unit testing automated test cases are often created by developers using the UnitTest framework.

Why Unit Testing Is Important?

Unit testing is crucial because it enables developers to find issues earlier in the development cycle, enhancing the caliber of software that is produced.
These are some wonderful advantages:

    1. Unit testing aids in the early detection of issues. This helps to save both time and money.
    1. We frequently don’t rewrite our code because we fear that doing so would destroy the unit. Unit testing offers us the assurance we need to rework our code.
    1. We can quickly comprehend the purpose of the unit by looking at the test cases.
    1. Debugging is easy to do. We can precisely identify the unit that the problem originates from because we are aware of the situations that are failing.

Usually, the unit is a function of the code.
It is also a component of “white box testing,” a kind of testing that may be created by a person who is familiar with the program’s design.


How To Write Unit Testing In Flutter

In the pubspec.yaml file, the dependency must first be included
Screen Shot 2022-08-02 at 23.52.42.png

The Structure should look like this:


Then create a class in the lib/test.dart file for this example, which is in charge of increasing and decreasing a number starting at 0.

    class Test {
      int value = 0; 
      void increment() => value++;  
      void decrement() => value--;

And finally write the test suite

    // Import the test package and Test class
      import 'package:test/test.dart';
      import 'package:test_app/test.dart';

    void main() {
      test('Test counter value should be incremented', () {
        final test = test();    
          expect(test.value, 1);

That’s it, now you can run your test case from your favorite IDE or you can run your test from the terminal using the following

    flutter test test/unit_test.dart

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