The Art of Unit Testing Understanding Why it‘s Importa

Author: Zen and the Art of Computer Programming

1 Introduction

Unit testing is an important methodology in the field of software engineering and the main criterion for measuring the quality of a project. A unit test is not a line in the code, but an independent test case for the entire software module or component. Before writing code, first write test code and test cases, and then integrate them into the development environment for automated running. Unit testing can find errors and defects in the code, thereby ensuring code quality and improving software reliability and security. Unit testing is an indispensable part of the entire software development life cycle. This article aims to introduce some basic concepts, terminology and principles behind unit testing, and how to apply it to various stages of the software development process.

2.1 Why unit testing? The purpose of unit testing is to find potential bugs, loopholes, logic errors and other errors in the code, and to verify whether these errors have been fixed. In software development, unit testing is one of the most basic and fundamental types of testing. Nowadays, more and more companies and organizations are requiring developers to perform unit testing, because unit testing can help developers find coding errors, debugging problems, and reduce failures when the software is actually running. In addition, unit testing can also help find errors in business logic, improve the maintainability of code, and also discover hidden performance bottlenecks and functional problems in large systems. In any case, unit testing is very necessary.

2.2 Testing strategies and goals The key to unit testing lies in the verb "test", not simply "test". The purpose of testing is to ensure that the code works properly under various input conditions. Therefore, unit testing needs to follow some basic testing strategies, such as layered testing, combination testing, dependency testing, etc. These strategies help guide the design, execution, and improvement of unit tests. According to different business needs, testing strategies will also vary. For example, for banking business systems, combination testing is generally not used, but more emphasis is placed on the function and performance of the subsystem in unit testing. Likewise, for e-commerce platforms, dependency testing may be appropriate. In summary, testing strategies often depend on the personal preferences of the software developer and the technical level of the development team.

2.3 Unit testing tools Unit testing is usually performed using automated tools, such as JUnit, Nunit, RSpec, etc. Automated testing tools provide test case templates, assertion libraries and related APIs, which greatly facilitate developers to conduct unit testing. Of course, some tools provide Web UI testing and can also perform unit testing in a browser environment. At the same time, there are some tools for integration testing and end-to-end testing, but the scope of use of these tools is relatively narrow.

2.4 Unit testing framework There are different unit testing frameworks for different programming languages. Such as JUnit in Java, MSTest in C#; unittest, pytest in Python; Mocha, Jasmine, etc. in JavaScript. Each language will have its own unit testing framework that it is good at, and you need to be familiar with them to write good unit tests.

2.5 Advantages of unit testing The advantages of unit testing are as follows:

Detect errors in advance: Unit testing is often used as a form of compilation testing during the development process, which can help developers find logical and grammatical errors in the code, thereby preventing these errors in advance from causing the code to run incorrectly.
Reduce costs: Unit testing can effectively reduce the time of development and testing and significantly reduce the cost of software development.
Improve code quality: Unit testing not only ensures the correctness of the code, but also improves the readability, robustness, scalability and maintainability of the code.
Increased stability: Unit testing improves software security by detecting vulnerable points in the code.
Promote software optimization: Unit testing can let developers know where optimization is needed, so they can focus on optimization.
Accelerate software development: Unit testing can improve the efficiency of software development, shorten software development time, and reduce the probability of developers making errors.

2.6 Steps of unit testing

Planning First, decide how many unit tests you should write. Set appropriate test goals based on factors such as project size, module complexity, and test difficulty.
Before you prepare to write unit tests, you need to be well prepared. Including, choosing appropriate testing tools, reading test documents, finding technical books, understanding software architecture, understanding the functions implemented by the code, defining test cases and expected results.
Execute creation and execution of test cases. Each test case should include information such as required inputs, expected outputs, actual outputs, and verification steps.
After the analysis test is completed, analyze the test results and view the pass rate, failure rate, coverage rate, regression test statistics, etc. of the test cases. By analyzing the results, existing problems are identified and subsequent testing work is formulated.
Iteratively pass feedback, modify test cases, and continue testing until satisfactory test results are achieved. If problems are encountered, the test plan is adjusted based on feedback and the test is re-executed.
Report: Write a test report, summarize the test results, describe the test situation, indicate the corresponding indicators, and indicate the opinions of relevant personnel.

3. Why unit testing?

The role of unit testing is to ensure that the code works correctly under various input conditions and prove that it behaves as expected. Unit testing has the following advantages:

Detect errors in advance: Unit testing can find errors in the code during the development process. Test cases are often used to automate testing and make errors found faster than manual testing.
Reduced costs: Unit testing can reduce the cost of developing tests because it can be run automatically and only part of the code will be tested.
Improve code quality: Unit testing can improve code readability, robustness, scalability, and maintainability.
Increased stability: Unit testing can find vulnerable points in the code and increase the security of the code.
Promote software optimization: Unit testing allows developers to understand the optimization space of the code and maintain the consistency and integrity of the code while optimizing the code.
Speed up software development: Unit testing can speed up software development because it can detect possible errors in advance without affecting other code.

4. Basic concepts of unit testing

4.1 Purpose of testing

The goal of unit testing is to determine whether the program behaves as expected under certain input conditions, that is, the code has good portability, stability, and testability. The purpose of unit testing is to find errors in the code and plays an important role in improving the reliability and security of the software.

4.2 Test cases

Test cases are performed by test engineers based on software specifications or development plans or software design documents, through a certain testing process, using a set of preset input data, expected output results and execution sequences to test computer software products or their components. Detailed instructions for conducting the test. Test cases usually contain three parts: input data, expected output results, and execution sequence.

4.3 Black box testing

Black box testing, also known as structural testing or data-driven testing, refers to the tester observing the function, performance, usability, and compatibility of the software system based on the provided data and interface call description without accessing the source code. Wait for the operating status to determine whether the actual operating results of the software system are consistent with the expected operating results. Testers do not need to understand the specific logic of the source code. They only need to use the provided data and interface call descriptions to simulate the behavior of the software system, and then check whether the actual running results are consistent with the expected running results. The advantage of the black box testing method is that it can comprehensively test the functions, performance, usability, compatibility, etc. of the software. The disadvantage is that it is only suitable for relatively simple systems.

4.4 White box testing

White box testing, also known as manual testing or code-level testing, refers to the tester analyzing, reading, and understanding the source code of the software system, and constructing input data, interface call descriptions, and expectations according to the design requirements by writing test cases. Output results, simulate the behavior of the software system, and then verify whether the real operating results of the software system's functions, performance, availability, compatibility, etc. are consistent with the expected operating results. The advantage of the white-box testing method is that it can comprehensively test the function, performance, usability, compatibility, etc. of the software. The disadvantage is that the tester needs to understand the internal logic of the source code and can only test relatively simple systems.

4.5 Gray box testing

Gray box testing is a testing method between black box testing and white box testing. This testing method isolates the object under test from the external factors of the software system by analyzing requirements, documents, design instructions, etc., combined with the status, variable values, execution paths, etc. of the program when it is running, and simulates the user's operating behavior to complete the test. Work. The characteristic of gray box testing method is that it combines the characteristics of black box testing and white box testing, and is suitable for more complex systems.

4.6 Module testing

Module testing refers to testers testing independent modules or subsystems in a software system. The purpose is to find out the quality problems of each module or subsystem in the software system, such as functionality, reliability, performance, compatibility, etc. . Module testing can be applied to different levels of software systems, from simple to complex, from small and medium-sized systems to large systems, and even across multiple levels of systems.

4.7 Regression testing

Regression testing, also known as regression testing, refers to a common testing technique in the software development process. It refers to re-running all previous test cases after new changes or updates, with the purpose of discovering new code Destruction of existing functions in order to correct errors and solve problems early. Regression testing is to ensure that no new errors are introduced during the development process of the software, and is one of the main means of software quality assurance.

4.8 Unit testing framework

Commonly used unit testing frameworks include: JUnit, TestNG, PHPUnit, Mocha/Chai, and Jasmine.

5. Unit testing process

The unit testing process generally includes the following steps:

Outline design: This step is to analyze and design the current system, decide the next step of testing work, identify the test cases to be written, and form a test plan.
Requirements analysis: This step confirms the functional requirements, performance requirements, usability requirements, compatibility requirements, recovery requirements, robustness requirements, etc. of the software, and then creates test cases to clarify test data and test processes.
Design test cases: This step analyzes the functions and performance of the module or subsystem, identifies various test points, and constructs test cases.
Coding test cases: This step is to write test case code according to the requirements of the test case, and implement automated unit testing by building test frameworks, modules, test cases, assertions and other tools.
Execute test cases: This step is to use automated tools to run the written test cases to detect the correctness, performance, compatibility, robustness and other quality dimensions of the code.
Analyze test results: This step is to analyze the test results, determine whether the test case passed, failed, time-consuming, etc., and formulate subsequent test work.
Report generation: This step is to organize the test results into a text report and form a detailed test report.
Evaluate the test plan: This step is to evaluate the test plan to see if there are any improvement points, add test cases, etc., and then make corresponding adjustments to ultimately achieve satisfactory test results.

6. Unit Test Example

The following takes Java as an example to show an example of unit testing:

public class Calculator {
    public int add(int num1, int num2){
        return num1 + num2;
    }

    public double subtract(double num1, double num2){
        return num1 - num2;
    }

    // other methods...
}

The corresponding unit test classes are as follows:

import static org.junit.Assert.*;
import org.junit.Before;
import org.junit.Test;

public class CalculatorTest {
    private Calculator calculator;

    @Before
    public void setUp() throws Exception {
        this.calculator = new Calculator();
    }

    @Test
    public void testAdd() {
        assertEquals("testAdd method failed", 5, this.calculator.add(2, 3));
    }

    @Test
    public void testSubtract() {
        assertEquals("testSubtract method failed", 1.5, this.calculator.subtract(3, 1.5), 0);
    }

    // more test cases...
}

The above is a simple case of a calculator class, which contains two methods add()and subtract(), and the corresponding test cases are testAdd()and testSubtract(). setUp()A method is an annotation in the test class that is used to initialize some parameters before executing the test case. assertEquals()Methods are used to verify that results are as expected. @TestAnnotations identify a test case.

7. Summary

This article mainly introduces the basic concepts, terminology and principles of unit testing, as well as why unit testing is performed. It uses the calculator class as an example to explain the various steps and framework of unit testing. Finally, the article summarizes the advantages, processes, principles, and examples of unit testing. I hope that through this article, readers can have a preliminary understanding of unit testing and become proficient in its use.