Java JUnit Library. Types of Testing

1. Testing in Development

Let's talk about types of testing and which testing methods developers use. You will learn about the stages an application goes through before being delivered to the client and the specific tests you will need to write.

What is Testing, and Why do We Need It

Types of Testing

2. Unit Tests

In this section, we're going to dive into unit testing — you'll get the rundown on its structure in Java and the ins and outs of crafting them the right way. Setting up your IDE, importing necessary libraries, and lots of hands-on practice.

Set-Up

Test-Driven Development

Creating Unit Tests

@BeforeEach

How to Test `void` Methods

Assertions

Assertions Practice

Section 2 Summary

3. Exceptions

In this section, we will enhance our coding skills by dealing with errors that can also be caught in unit tests. When testing an application, you may come across various errors, and sometimes they should be turned into exceptions. I will explain how to catch exceptions in your code, test them, and handle them properly.

Throwing Exceptions

Try-catch structure

Handling Multiple Exceptions

Handling Exceptions Practice

Creating Exceptions

Testing Exceptions

Testing Exceptions Practice

Try-catch structure

How to Handle Exceptions

From the previous chapter, you may have understood that exceptions completely halt the program's execution. Such an outcome is not desirable for us because we need the program to continue running without crashing.

Simply removing exceptions is not an option, as in that case, the program would work incorrectly. Therefore, we need to learn how to handle errors using the try-catch structure.

In Java, the try-catch structure is a mechanism for catching and handling exceptions, ensuring that the program execution flow can continue even after an error occurs.

Let's take a look at the syntax of such a structure and understand how it captures errors:

try Block: This block contains the code that might generate an exception. During execution, if any statement within the try block throws an exception, the rest of the block's code is skipped, and the control moves to the corresponding catch block(s) to handle that exception;
catch Block: This block is used to handle the exception. It must follow the try block. If the type of exception thrown matches the type declared in the catch block, the code inside this block is executed. There can be multiple catch blocks associated with a single try block, each catching and handling different types of exceptions.

In simpler terms, we attempt to execute the code, preparing to catch an exception. If we catch an exception, the code execution doesn't stop but continues with the operation specified in the catch block. If there's no exception, the operation is executed successfully without entering the catch block.

Handling ArithmeticException

In the previous chapter, we implemented a division method that throws an arithmetic exception in case of division by zero. Here's what this method looks like:

Now, let's handle this exception when calling the method using a try-catch structure:

main.java

As you can see, we attempt to perform division by zero, but we do it within the try block. In the catch block, we catch the ArithmeticException and give it an alias "e" so that we can use this object in the future (remember, exceptions are objects, right?).

This way, the exception doesn't halt the program's execution since we've handled it. Now, in the event of an exception being thrown, the program notifies the user with console output and continues its execution.

1. What is the purpose of the `try` block in a try-catch structure?

2. What happens if an exception is thrown inside a `try` block?

3. What does the `catch` block do in a try-catch structure?

4. What is the result of handling an exception with a `try-catch` structure?

What is the purpose of the try block in a try-catch structure?

Виберіть правильну відповідь

To define the exception that needs to be caught

To contain the code that might generate an exception

To handle the exception that has been caught

What happens if an exception is thrown inside a try block?

Виберіть правильну відповідь

The program immediately exits

The rest of the code inside the try block continues to execute

The execution of the try block is interrupted and control moves to the corresponding catch block

What does the catch block do in a try-catch structure?

Виберіть правильну відповідь

It throws an exception

It handles the exception thrown by the try block

It ignores any exceptions that occur

What is the result of handling an exception with a try-catch structure?

Виберіть правильну відповідь

The program continues executing even if an exception occurs

The exception is prevented

The program stops executing

Все було зрозуміло?

Секція 3. Розділ 2

Зміст курсу

Java JUnit Library. Types of Testing

1. Testing in Development

What is Testing, and Why do We Need It Types of Testing Application Stages Unit Testing Integration Testing Functional Testing Section 1 Summary

2. Unit Tests

Set-Up Test-Driven Development Creating Unit Tests @BeforeEach How to Test `void` Methods Assertions Assertions Practice Section 2 Summary

3. Exceptions

Throwing Exceptions Try-catch structure Handling Multiple Exceptions Handling Exceptions Practice Creating Exceptions Testing Exceptions Testing Exceptions Practice

Java JUnit Library. Types of Testing

Try-catch structure

How to Handle Exceptions

Simply removing exceptions is not an option, as in that case, the program would work incorrectly. Therefore, we need to learn how to handle errors using the try-catch structure.

In Java, the try-catch structure is a mechanism for catching and handling exceptions, ensuring that the program execution flow can continue even after an error occurs.

Let's take a look at the syntax of such a structure and understand how it captures errors:

try Block: This block contains the code that might generate an exception. During execution, if any statement within the try block throws an exception, the rest of the block's code is skipped, and the control moves to the corresponding catch block(s) to handle that exception;
catch Block: This block is used to handle the exception. It must follow the try block. If the type of exception thrown matches the type declared in the catch block, the code inside this block is executed. There can be multiple catch blocks associated with a single try block, each catching and handling different types of exceptions.

Handling ArithmeticException

In the previous chapter, we implemented a division method that throws an arithmetic exception in case of division by zero. Here's what this method looks like:

Now, let's handle this exception when calling the method using a try-catch structure:

main.java

1. What is the purpose of the `try` block in a try-catch structure?

2. What happens if an exception is thrown inside a `try` block?

3. What does the `catch` block do in a try-catch structure?

4. What is the result of handling an exception with a `try-catch` structure?

What is the purpose of the try block in a try-catch structure?

Виберіть правильну відповідь

To define the exception that needs to be caught

To contain the code that might generate an exception

To handle the exception that has been caught

What happens if an exception is thrown inside a try block?

Виберіть правильну відповідь

The program immediately exits

The rest of the code inside the try block continues to execute

The execution of the try block is interrupted and control moves to the corresponding catch block

What does the catch block do in a try-catch structure?

Виберіть правильну відповідь

It throws an exception

It handles the exception thrown by the try block

It ignores any exceptions that occur

What is the result of handling an exception with a try-catch structure?

Виберіть правильну відповідь

The program continues executing even if an exception occurs

The exception is prevented

The program stops executing

Все було зрозуміло?

Секція 3. Розділ 2