如何用 Java 编写测试用例
- WBOY原创
- 2024-08-12 18:40:36739浏览
编写测试用例是确保代码可靠性和健壮性的一项基本技能。测试用例可以帮助识别错误并验证代码是否按预期工作。
测试用例可以使用任何编程语言（如 Java、Python、C# 等）编写。然而，由于 Java 强大的社区支持以及与项目需求的一致性，许多测试人员更喜欢用 Java 编写测试用例。使用 Java 自动化这些测试用例可以帮助测试人员节省执行时间并在测试的早期阶段捕获错误。
Java 中的测试用例是什么？
Java 是自动化测试最常用的编程语言之一。用 Java 编写测试用例意味着构建遵循并实现 OOP 概念的整个自动化项目。这使得项目和测试用例更加健壮，并且整个代码被分类为许多类和方法，使其更易于维护和使用。
自动化测试用例有助于在回归时快速测试功能，并有助于节省大量手动工作。这些测试用例在网页上执行一些流程，然后使用断言来验证输出是否与所需的输出匹配。
例如，对于 LambdaTest Selenium Playground 页面上的两个输入字段部分，一些测试用例如下所示：
- 验证页面上是否存在所有标签、文本输入框和按钮。
- 输入两个数字时，验证总和是否正确显示在“结果”下。
- 如果未输入一个或两个数字，请验证结果下是否显示错误消息。
在用Java编写测试用例时，需要考虑一些事情，比如测试流程、测试范围、命名、断言、测试数据、分组、定位WebElements等。如果使用得当，所有这些都会成为一个好的测试随着更多变化的到来，这种情况在将来很容易理解和维护。
但是，开始测试流程的初始操作是找到一个 WebElement，您必须用 Java 为其编写有效的测试用例。
在 Java 中定位 WebElement
关于用 Java 编写测试用例需要了解的另一件事是定位 WebElements。这是必需的，因为测试用例流将与这些 WebElement 交互以执行输入数据、单击按钮、检索数据等操作以获取结果。在 Selenium 中查找 WebElement 定位器有多种方法，例如 ID、Name、CSS、XPath、linkText、 等
在演示如何用 Java 编写测试用例之前，让我们了解如何使用其定位器策略来定位测试流程中使用的不同 WebElement。我们将使用 XPath 或 ID 定位器来定位此测试用例的所有 WebElement。
您可以使用最常见的方法之一来查找元素，即 Selenium 中的 findElement()。
- 要使用 XPath 从 LambdaTest Selenium Playground 页面找到 两个输入字段 标签，您可以使用以下 XPath 表达式：
driver.findElement(By.xpath("//*[contains(text(),'Two')]"));
- 要使用 XPath 从 LambdaTest Selenium Playground 页面找到 输入第一个值 标签，您可以使用以下 XPath 表达式：
driver.findElement(By.xpath("//*[contains(text(),'first value')]"));
- 要使用 XPath 从 LambdaTest Selenium Playground 页面找到 输入第二个值 标签，您可以使用以下 XPath 表达式：
driver.findElement(By.xpath("//*[contains(text(),'first value')]"));
- 要使用 XPath 从 LambdaTest Selenium Playground 页面找到 Get Sum 按钮，您可以使用以下 XPath 表达式：
driver.findElement(By.xpath("//*[contains(text(),'Sum')]"));
- 要使用 ID 从 LambdaTest Selenium Playground 页面查找 第一个值 文本框，您可以使用以下 ID 表达式：
driver.findElement(By.id("sum1"));
- 要使用 ID 从 LambdaTest Selenium Playground 页面查找 第二个值 文本框，您可以使用以下 ID 表达式：
driver.findElement(By.id("sum2"));
- 要使用 ID 从 LambdaTest Selenium Playground 页面查找 Result 标签，您可以使用以下 ID 表达式：
driver.findElement(By.id("user-message"));
- 要使用 ID 从 LambdaTest Selenium Playground 页面查找 结果/错误消息，您可以使用以下 ID 表达式：
driver.findElement(By.id("addmessage"));
您还可以参考这个 Selenium 定位器指南来了解如何在 Java 中编写测试用例时定位 WebElements。
如何用Java编写测试用例？
在用 Java 编写有效的测试用例之前，您必须使用所有必需的库和工具设置项目。我们将使用 Eclipse IDE 演示 Maven 项目的设置。此外，我们将添加 TestNG 作为测试框架来处理测试执行并实现设置和拆卸方法。
在本次演示中，我们首先将编写 3 个测试用例来涵盖提到的所有 Java 测试用例，并实施所有适用的最佳实践。
测试场景 1：
导航到 Selenium Playgrounds 上的两个输入字段部分（简单表单演示）
断言此部分的所有 WebElement 的可见性
识别 两个输入字段 标签的定位器。
识别**第一个**和**第二个**值标签的定位器。
识别**第一个**和**第二个**值输入框的定位器。
识别 获取总和 按钮的定位器。
结果标签。
测试场景 2 :
导航到 Selenium Playgrounds（简单表单演示）页面上的 两个输入字段 部分。
在两个输入框中输入有效值。
点击获取总和按钮。
断言总和正确并显示在 **结果 **标签下。
测试场景 3 :
导航到 Selenium Playgrounds（简单表单演示）页面上的 两个输入字段 部分。
在任一输入框中输入值。
点击获取总和按钮。
断言错误消息显示在结果标签下。
让我们开始安装必要的库，因为我们已经有了测试流程并准备好使用工具和库。
项目设置：
如前所述，我们将使用 Eclipse IDE 用 Java 编写测试用例。但是，您可以使用任何 IDE 来编写测试用例。您只需要创建一个新的 Maven 项目即可。
启动 Eclipse IDE 并通过单击“文件”>“新建项目”向导打开“新建项目”向导。新的>项目。
在“向导”下，展开 Maven，选择 Maven 项目，然后单击“下一步”。
单击“创建一个简单的项目”复选框，然后单击“下一步”。
在此新建 Maven 项目向导中，输入 Group Id 和 Artifact Id，然后单击 Finish 创建您的项目。在这里，Group Id 是帮助识别一个项目组与另一个项目组的唯一名称，Artifact Id 是为我们将创建的项目指定的唯一名称。
项目创建后，项目结构的根文件夹中将包含一个 pom.xml 文件。在这里，我们将添加用 Java 编写和执行自动化测试用例所需的依赖项。由于我们将使用 TestNG 作为测试框架，因此我们将添加它的依赖项。此外，我们将添加 Selenium 依赖项，因为我们将编写的测试用例涉及 Web 自动化。
You can fetch the latest TestNG and Selenium dependencies from the Maven Repository.
The updated pom.xml would look like the one below.
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>demo.lambdaTest</groupId>
<artifactId>JavaTestCase</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<version>7.10.1</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-java</artifactId>
<version>4.21.0</version>
</dependency>
</dependencies>
</project>
The next step is to add the test class files where we will write the test case in Java. Add 2 Java class files under src/test/java package.
BaseTest.java: This file will have the setup() and tearDown() methods to create and remove the *WebDriver *instances for test cases.
**TwoInputFieldTests.java: **This file will be the test class file where all the test cases discussed above will be written.
The completed BaseTest.java would look like the one below.
package LocalGrid;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.*;
public class BaseTest {
public static WebDriver driver;
@BeforeMethod
public void setup()
{
driver = new ChromeDriver();
System.out.println("Navigating to Two Input Field section");
driver.get("https://www.lambdatest.com/selenium-playground/simple-form-demo");
}
@AfterMethod
public void tearDown()
{
driver.quit();
}
}
Code Walkthrough:
Below is the complete code walkthrough to understand the code written in the above BaseTest.java file.
- In this class, create a WebDriver instance, which will be used to interact with the browser, then create the first method as setup() and annotate it with the @BeforeMethod. @BeforeMethod is a TestNG annotation. This annotation helps invoke this method before executing each test method, i.e., each test case. This will help create a new WebDriver instance for each test case in Java and navigate to the website.
- Initialize the driver variable with the ChromeDriver() class. This will execute all the test cases in Java on the Chrome browser.
- Use the get() method of Selenium WebDriver to navigate to the test webpage on LambdaTest Playground.
- Add the next method, tearDown(), and annotate it with @AfterMethod annotation to execute it after each test case in Java is executed. @AfterMethod is called the quit() method, which quits the driver instance and closes the open browser windows.
With this, the BaseTest file is created, and we are ready to create a test file to run the test case in Java.
Create a file called TwoInputFieldTests.java. This file will contain all the code for the test scenarios discussed earlier.
package LocalGrid;
import org.openqa.selenium.By;
import org.testng.Assert;
import org.testng.annotations.Test;
public class TwoInputFieldTests extends BaseTest
{
@Test(groups = {"uiTest"})
public void shouldVerifyAllElementsWhenThePageIsLoaded()
{
System.out.println("Verify Two Input Fields title is displayed.");
Assert.assertTrue(driver.findElement(By.xpath("//*[contains(text(),'Two')]")).isDisplayed());
System.out.println("Verify enter first value label is displayed.");
Assert.assertTrue(driver.findElement(By.xpath("//*[contains(text(),'first value')]")).isDisplayed());
System.out.println("Verify enter first value textbox is displayed.");
Assert.assertTrue(driver.findElement(By.id("sum1")).isDisplayed());
System.out.println("Verify enter second value label is displayed.");
Assert.assertTrue(driver.findElement(By.xpath("//*[contains(text(),'second value')]")).isDisplayed());
System.out.println("Verify enter second value textbox is displayed.");
Assert.assertTrue(driver.findElement(By.id("sum2")).isDisplayed());
System.out.println("Verify Get Sum button is displayed.");
Assert.assertTrue(driver.findElement(By.xpath("//*[contains(text(),'Sum')]")).isDisplayed());
System.out.println("Verify result label is displayed.");
Assert.assertTrue(driver.findElement(By.id("user-message")).isDisplayed());
}
@Test(groups = {"positiveTest", "sanity"})
public void shouldReturnTheResultWhenBothNumbersAreValid()
{
System.out.println("entering first value");
driver.findElement(By.id("sum1")).sendKeys("5");
System.out.println("entering second value");
driver.findElement(By.id("sum2")).sendKeys("10");
System.out.println("click on sum");
driver.findElement(By.xpath("//*[contains(text(),'Sum')]")).click();
System.out.println("fetch the result and assert it");
String result = driver.findElement(By.id("addmessage")).getText();
Assert.assertEquals(result, "15", "Sum is incorrect. Expected : 15 but Found : " + result);
}
@Test(groups = {"errorTest", "sanity"})
public void shouldShowErrorWhenAnyNumberIsMissing()
{
System.out.println("entering first value");
driver.findElement(By.id("sum1")).sendKeys("5");
System.out.println("click on sum");
driver.findElement(By.xpath("//*[contains(text(),'Sum')]")).click();
System.out.println("fetch the error message and assert it");
String errorMessage = driver.findElement(By.id("addmessage")).getText();
String expectedError = "Entered value is not a number";
Assert.assertEquals(errorMessage, expectedError, "Incorrect error message. Expected : " + expectedError + " but Found : " + errorMessage);
}
}
``
**Code Walkthrough:**
Below is the complete code walkthrough to understand the code written in the above TwoInputFieldTests.java file.
1. Add a new class file as TwoInputFieldTests.java and extend BaseTest. This helps to inherit and access the *driver* variable and methods of the base class in all the test cases and prevents redundant code.
1. Add the first test case as *shouldVerifyAllElementsWhenThePageIsLoaded()* and *annotate* it with the *@Test* annotation. This annotation helps to identify a method as a test case and execute it as a TestNG case. We have used the *groups* attribute of *@Test* annotation here to mark this test as part of the *uiTests* group so that it gets executed whenever these group cases are triggered.
1. In this test case, we verify if all the Two Input Fields section elements are displayed when the web page is loaded.
1. For this, we use the *isDisplayed()* method of WebElement to check whether the element is displayed. This returns a boolean *true* value if the element is displayed and *false* if not.
1. To assert the same, we use the *assertTrue()* method of the *Assert* class. It passes if the passed value is true, meaning the element is displayed.
Assertions are crucial in the automation testing process, ensuring the software functions as expected. To learn assertTrue(), follow this guide on assertTrue() in Java and gain valuable insights.
1. Write a similar assert statement using the *isDisplayed()* method for all the web elements to verify the entire UI of this section.
1. Add the second test case as *shouldReturnTheResultWhenBothNumbersAreValid*(). Similar to the previous case, annotate it with the *@Test* annotation and add it to *positiveTest* and *sanity* groups. We have added 2 group names here, unlike 1 in the previous case. This means that this test case in Java will get executed as part of both these groups.
1. Enter the first and second values using the *sendKeys()* method. This method of Selenium WebDriver is used to enter data in any input text box field while working with web automation.
1. After entering the values, click the **Get Sum** button to get the result. For this, another method of WebDriver, *click()* is used.
1. Finally, we fetch the result using the *getText()* method and store it in a variable. This method retrieves any text value from the web page using Selenium web automation. Assert’s a*ssertEquals()* method compares this value with the expected result.
This method is used to compare two values as part of an assertion. Learn how to use asserts in TestNG correctly to help you verify and validate your actual and expected results.
1. Add the last test case and name it as *shouldShowErrorWhenAnyNumberIsMissing()*. Like the previous cases, annotate it with *@Test* and add it to the *negativeTest *and *sanity *groups.
1. Enter any one value using the *sendKeys()* method. Here, we are entering the first value field.
1. Click on the **Get Sum** button.
1. Fetch the error message using the *getText()* method and assert it to be the same as the expected error message using the *assertEquals()* method.
**Test Execution And Results**
Right-click > Select Run As > TestNG, Test to execute the tests individually.
**Result:**
*shouldVerifyAllElementsWhenThePageIsLoaded()*
**Result:**
*shouldReturnTheResultWhenBothNumbersAreValid()*
**Result:**
*shouldShowErrorWhenAnyNumberIsMissing()*
Running tests locally is manageable when working with up to three or four browsers and one operating system. However, this limitation makes it difficult for testers to conduct tests on more than four browsers and multiple operating systems. To address this, testers can use a cloud-based platform where they do not have to worry about maintaining test infrastructure and can conduct comprehensive cross-browser and cross-platform testing seamlessly. One such platform is LambdaTest.
It is an AI-powered test execution platform that lets you run manual and automated [cross-browser testing](https://www.lambdatest.com/cross-browser-testing?utm_source=medium&utm_medium=organic&utm_campaign=aug_12&utm_term=rj&utm_content=blog) at scale, with over 3000+ real devices, browsers, and OS combinations.
This platform provides the speed and resources to make test executions faster and more reliable. It facilitates parallel execution, allowing multiple tests to run simultaneously for large automation suites. This cloud grid platform also offers enhanced logging, maintenance, and debugging resources.
Now, let’s move the local test script to the LambdaTest platform with a few modifications to leverage all the features this cloud grid offers.
## How To Write a Test Case in Java for Cloud Execution?
Having understood the flow of writing and executing the first test case in Java using Selenium and TestNG, let us move ahead and learn how we can do the same on a cloud grid platform.
To use the LambdaTest cloud grid to run the Selenium automation test cases, we need to make some changes to the code to use Selenium *RemoteWebDriver*, which will help connect to the LambdaTest cloud grid and execute the cases over there.
Most of these changes involve configuring the WebDriver settings in BaseTest.java. The modified BaseTest.java with the cloud grid integration will look similar to the example below.
package CLoudGRid;
import java.net.*;
import java.util.HashMap;
import org.openqa.selenium.remote.RemoteWebDriver;
import org.openqa.selenium.chrome.ChromeOptions;
import org.testng.annotations.*;
public class BaseTest {
public RemoteWebDriver driver = null;
String username = System.getenv("LT_USERNAME") == null ? "<lambdatest_username>" : System.getenv("LT_USERNAME");
String accessKey = System.getenv("LT_ACCESS_KEY") == null ? "<lambdatest_accesskey>" : System.getenv("LT_ACCESS_KEY");
String status = "failed";
@BeforeMethod
public void setup() {
try {
ChromeOptions chromeOptions = new ChromeOptions();
chromeOptions.setPlatformName("Windows 10");
chromeOptions.setBrowserVersion("125");
HashMap<String, Object> ltOptions = new HashMap<String, Object>();
ltOptions.put("build", "Test case in Java");
ltOptions.put("name", "Test case in Java");
ltOptions.put("w3c", true);
chromeOptions.setCapability("LT:Options", ltOptions);
driver = new RemoteWebDriver(
new URL("https://" + username + ":" + accessKey + "@hub.lambdatest.com/wd/hub"), chromeOptions);
System.out.println("Navigating to Two Input Field section");
driver.get("https://www.lambdatest.com/selenium-playground/simple-form-demo");
} catch (MalformedURLException e) {
e.printStackTrace();
}
}
@AfterMethod
public void tearDown() {
driver.executeScript("lambda-status=" + status);
driver.quit();
}
}
**Code Walkthrough:** Below is the complete code walkthrough to understand the code written in the above BaseTest.java file. 1. Start by creating required class objects and variables with public access to access them in the test classes. For this, first, create an object of *RemoteWebDriver* and initialize it to null.  1. Next, add the username and access key for your LambdaTest account to connect to the cloud grid for test execution. You can find these in the [Password & Security](https://accounts.lambdatest.com/security) section tab.  1. You can also configure these as environment variables and directly fetch them in code instead of defining them in plain text. **For Windows:** > set LT_USERNAME=LT_USERNAME set LT_ACCESS_KEY=LT_ACCESS_KEY **For macOS and Linux:** > export LT_USERNAME=LT_USERNAME export LT_ACCESS_KEY=LT_ACCESS_KEY 1. Add a String variable as *status* and initialize it with value as *failed*. Before quitting the driver instance, this variable helps mark the test case’s final status as passed/failed on the LambdaTest dashboard. This value is updated to be *passed* in the test case if the test passes with no assertion failures or exceptions.  1. Update the code inside the *setup()* method to set the required browser properties and LambdaTest configurations to connect to the cloud grid. 2. Create an object of the *ChromeOptions *class and set the OS and browser versions.  1. Next, create a *HashMap* type variable to specify the additional browser capabilities for the LambdaTest platform. This will help to identify the dashboard test results using the build name and other details.  You can fetch the required browser capabilities from the LambdaTest platform by navigating to the [Automation Capabilities Generator](https://www.lambdatest.com/capabilities-generator/). This helps by offering ready-to-use code for setting up browser capabilities that can be used in execution.  1. Finally, use the Selenium *RemoteWebDriver* to connect to the LambdaTest remote grid using your credentials and *ChromeOptions* class object containing all specified browser capabilities.  1. Use this driver to navigate the Two Input Fields page on the LambdaTest Selenium Playground for test execution.  1. Inside the *tearDown()* method, add a step to execute the script to update the test case status on the LambdaTest dashboard.  1. Next, move to the test class TwoInputFieldTests.java and add the step to update the status to *passed *after the execution of all test cases.    **Results:** We can execute the test cases similarly to how we did for local execution. The console output in the IDE will remain unchanged, but the primary focus will shift to monitoring the execution results on the LambdaTest dashboard. The execution results are on the LambdaTest Dashboard under the **Automation > Web Automation** tab.     ## Best Practices for Writing Test Cases in Java All the test executions we’ve learned above are written following best practices. Adhering to these practices helps avoid repeating the same or similar mistakes and ensures a smooth test flow in your automation projects. Some of the best practices are given below. * **Understanding the Requirements** The first and foremost requirement of writing a good test case is understanding the changes and features clearly. The tester needs to know what is expected from the code based on the input. We can refer to the product requirement documentation or the acceptance cases to know the expected behavior. * **Maintainable and Reusable Code** The test cases should be readable and follow clean coding principles. This helps to keep test cases maintainable and allows quick refactoring in case of requirement changes without much hassle. * **Clear and Descriptive Test Case Names** The names should be clear and meaningful so that anyone who sees the code or test case can understand what a particular test is supposed to do. The name should be descriptive enough to describe the purpose of the test case. One of the naming conventions one can follow is *should[ExpectedResult*]*When[Condition]*. For example, *shouldReturnTheResultWhenBothNumbersAreValid *or *shouldShowErrorWhenAnyNumberIsMissing*. * **Arrange-Act-Assert Structure** Try to follow the AAA structure for your test cases for effective test management by splitting it into three parts. * **Arrange:** Define and set up the test environment and test data on which we want to execute the test. * **Act:** Write the execution steps which interact with the feature using the above data. * **Assert:** Write proper assertions which verify the actual and expected results. * **One Test Case, One Assertion** Use specific and meaningful assertions for each test case, which helps to verify the required details. One test should not be used to verify multiple flows and should not have a dependency on any other test case. For example, valid results for valid input and error responses for invalid input should be two separate test cases. You can use assertions like *assertEquals(), assertTrue(), assertFalse(), assertNotNull()*, etc., to assert to-the-point data and provide meaningful messages to better understand the failures. * **Using Setup and Teardown Methods** Use *@Before* and *@After* annotations of JUnit or TestNG, depending on your framework, to write setup and teardown methods. These methods help to prevent duplicity by making the common code, like driver setup, browser launch, driver termination, etc, reusable across all the test cases. * **Using Mock Data and Stubs for Error Cases** Mock data or stubs means to simulate a function behavior in the software to return some particular result as desired by the tester to test some particular test cases. We can use mocking frameworks like Mockito or write a stub function to mock dependencies and verify test cases for external dependency failures. * **Covering Edge and Boundary Value Cases** Write test cases to cover all the edge cases or unusual scenarios due to software or hardware downtimes. You can use mocking for such types of test cases. Also, testing for boundary values by passing various test data helps verify if the code and software function properly for limiting cases. * **Using Tags, Groups, and Categories** Use tags, groups, or categories to group the related test cases together that serve some common purpose, flow, or requirement in general. For instance, you can group all test cases for login flow, positive and negative cases, etc. ## Conclusion With this, we have concluded this blog on how to write a test case in Java. In this blog, we learned how a good test case can be written with a basic understanding of Java language and test case fundamentals like flow, assertions, and WeElement locators. We learned the working examples on local and cloud grids and understood how following the best practices makes the test case robust and reliable. Now, it’s time for you to go ahead and try writing your first [test case](https://www.lambdatest.com/learning-hub/test-case?utm_source=medium&utm_medium=organic&utm_campaign=aug_12&utm_term=rj&utm_content=blog) in Java. Happy learning!!
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