5.15. Introduction to Object Oriented Programming in Dart: Unit Testing

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Object-oriented programming (OOP) is a programming paradigm that uses the idea of ​​"objects", which can contain both data and code: data in the form of fields (also known as attributes or properties), and code, in the form of fields. form of procedures (also known as methods). OOP is one of the main pillars of the Dart language and, consequently, of Flutter.

Before we dive into unit testing, let's understand the basics of object-oriented programming in Dart. OOP in Dart is based on some main characteristics: classes, objects, inheritance, polymorphism, encapsulation and abstraction.

Classes and Objects

A class is a blueprint or blueprint for creating objects. An object is an instance of a class. For example, if we have a class called 'Car', then 'Ferrari', 'Toyota', etc. are objects of that class. Classes in Dart are defined using the 'class' keyword and objects are created using the 'new' operator.

Inheritance

Inheritance is a mechanism that allows a new class to acquire the properties and methods of an existing class. The existing class is called the base class and the new class is called the derived class. In Dart, inheritance is implemented using the 'extends' keyword.

Polymorphism

Polymorphism is the ability of an object to take many forms. In Dart, polymorphism is implemented using 'interface' and 'implements'.

Encapsulation

Encapsulation is the process of hiding the implementation details and exposing only the functionality to the user. In Dart, this is done using access modifiers: '_ '(private), '__' (protected) and no modifier (public).

Abstraction

Abstraction is the process of hiding complex details and showing only essential functionality. In Dart, this is done using abstract classes and abstract methods.

Unit Tests

Once you understand OOP in Dart, we can move on to unit testing. Unit tests are a way to verify that a small piece of code is working as expected. They are used to test the functionality of a specific method or class.

In Dart, the 'test' library is used to write unit tests. You can install the library by adding it to your 'pubspec.yaml' file. Once installed, you can import it into your test file using 'import package:test/test.dart'.

A Dart unit test usually has three parts: setup, execution, and verification. The setup is where you configure the required state for the test. Execution is where you run the code you want to test. And verification is where you verify that the result is what you expected.

Here is an example of a Dart unit test:

void main() {
  test('Addition test', () {
    // Setup
    var num1 = 5;
    var num2 = 10;

    // Execution
    var result = num1 + num2;

    // Verification
    expect(result, 15);
  });
}

This test checks that adding 5 and 10 equals 15. If the test passes, the addition is working correctly. If the test fails, there is a problem that needs to be fixed.

Unit tests are an essential part of software development. They help find and fix bugs before software is released. They also help ensure that code changes don't break existing functionality.

In summary, object-oriented programming in Dart is a fundamental concept for developing Flutter applications. Unit tests, on the other hand, are an essential tool for ensuring the quality and stability of your code. Therefore, learning and understanding these concepts is crucial to becoming an effective Flutter developer.

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