JUnit5 教程

JUnit5教程

在这个JUnit教程中，我们将使用例子介绍JUnit5的基础知识和新功能。在Java世界中，JUnit是用于对java代码进行单元测试的流行框架之一。JUnit主要帮助开发人员自己在JVM上测试他们的代码。

JUnit5架构

JUnit 平台

• Launches testing frameworks on the JVM
• Has TestEngine API used to build a testing framework that runs on the JUnit platform

JUnit Jupiter可以被改写为：JUnit 木星

• Blend of new programming model for writing tests and extension model for extensions
• Addition of new annotations like @BeforeEach, @AfterEach, @AfterAll, @BeforeAll etc.

JUnit传统版

• Provides support to execute previous JUnit version 3 and 4 tests on this new platform

JUnit的Maven依赖

为了在项目中实现基于JUnit5的测试用例，需要将以下依赖项添加到项目的pom.xml文件中。

• JUnit 5 Library

<dependency>
     <groupId>org.junit.jupiter</groupId>
     <artifactId>junit-jupiter-engine</artifactId>
     <version>5.1.1</version>
     <scope>test</scope>
</dependency>
<dependency>
     <groupId>org.junit.platform</groupId>
     <artifactId>junit-platform-runner</artifactId>
     <version> 1.1.1</version>
     <scope>test</scope>
</dependency>

• JUnit5 maven surefire provider to execute the unit tests where IDE does not have JUnit5 support (if IDE has support then this point is not required)

<plugin>
     <artifactId>maven-surefire-plugin</artifactId>
     <version>2.19.1</version>
     <dependencies>
          <dependency>
               <groupId>org.junit.platform</groupId>
               <artifactId>junit-platform-surefire-provider</artifactId>
               <version>1.0.2</version>
          </dependency>
     </dependencies>
</plugin>

JUnit5新功能

运行时需要Java 8或更高版本。但是可以使用之前的Java版本编译的代码进行测试。其中引入了各种新功能。

JUnit注解

以下是提供的一些常用注解：

package com.Olivia;

import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Disabled;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

public class JUnit5Sample1Test {

  @BeforeAll
  static void beforeAll() {
    System.out.println("**--- Executed once before all test methods in this class ---**");
  }

  @BeforeEach
  void beforeEach() {
    System.out.println("**--- Executed before each test method in this class ---**");
  }

  @Test
  void testMethod1() {
    System.out.println("**--- Test method1 executed ---**");
  }

  @DisplayName("Test method2 with condition")
  @Test
  void testMethod2() {
    System.out.println("**--- Test method2 executed ---**");
  }

  @Test
  @Disabled("implementation pending")
  void testMethod3() {
	  System.out.println("**--- Test method3 executed ---**");
  }

  @AfterEach
  void afterEach() {
    System.out.println("**--- Executed after each test method in this class ---**");
  }

  @AfterAll
  static void afterAll() {
    System.out.println("**--- Executed once after all test methods in this class ---**");
  }


}

JUnit断言

每个测试方法必须使用断言来对条件进行评估以使测试能够继续执行。JUnit Jupiter的断言存储在org.junit.jupiter.api.Assertions类中，所有方法都是静态的。

@Test
void testAssertEqual() {
	 assertEquals("ABC", "ABC");
	 assertEquals(20, 20, "optional assertion message");
	 assertEquals(2 + 2, 4);
}

@Test
void testAssertFalse() {
	 assertFalse("FirstName".length() == 10);
	 assertFalse(10 > 20, "assertion message");
}

@Test
void testAssertNull() {
     String str1 = null;
	 String str2 = "abc";
	 assertNull(str1);
	 assertNotNull(str2);	
}

@Test
void testAssertAll() {
	 String str1 = "abc";
	 String str2 = "pqr";
	 String str3 = "xyz";
	 assertAll("numbers",
	      () -> assertEquals(str1,"abc"),
		  () -> assertEquals(str2,"pqr"),
		  () -> assertEquals(str3,"xyz")
	 );
	 //uncomment below code and understand each assert execution
     /*assertAll("numbers",
		  () -> assertEquals(str1,"abc"),
		  () -> assertEquals(str2,"pqr1"),
		  () -> assertEquals(str3,"xyz1")
	 );*/
}

@Test
void testAssertTrue() {
	 assertTrue("FirstName".startsWith("F"));
	 assertTrue(10  {
	      throw new IllegalArgumentException("Illegal Argument Exception occured");
	 });
	 assertEquals("Illegal Argument Exception occured", exception.getMessage());
}

JUnit5 的导入

它的测试类需要导入org.junit.jupiter.api.Test语句而不是org.junit.Test。另外，测试方法不需要公共和本地包。

import org.junit.jupiter.api.Test;

JUnit5的假设

假设是在org.junit.jupiter.api.Assumptions类中的静态方法。只有满足指定条件时，它们才会执行测试，否则测试将被中止。中止的测试不会导致构建失败。当假设失败时，会抛出org.opentest4j.TestAbortedException并跳过该测试。

@Test
void testAssumeTrue() {
     boolean b = 'A' == 'A';
     assumeTrue(b);
     assertEquals("Hello", "Hello");
}

@Test
@DisplayName("test executes only on Saturday")
public void testAssumeTrueSaturday() {
     LocalDateTime dt = LocalDateTime.now();
     assumeTrue(dt.getDayOfWeek().getValue() == 6);
     System.out.println("further code will execute only if above assumption holds true");
}

@Test
void testAssumeFalse() {
     boolean b = 'A' != 'A';
     assumeFalse(b);
     assertEquals("Hello", "Hello");
}

@Test
void testAssumeFalseEnvProp() {
     System.setProperty("env", "prod");
     assumeFalse("dev".equals(System.getProperty("env")));
     System.out.println("further code will execute only if above assumption hold");
}

@Test
void testAssumingThat() {
     System.setProperty("env", "test");
     assumingThat("test".equals(System.getProperty("env")),
          () -> {
               assertEquals(10, 10);
               System.out.println("perform below assertions only on the test env");
               });

     assertEquals(20, 20);
     System.out.println("perform below assertions on all env");
}

JUnit 嵌套测试类

嵌套测试允许创建嵌套类并执行其中的所有测试方法。内部类必须是非静态的。只需用@Nested注释内部类，内部类中的所有测试方法都将被执行。

@BeforeAll
static void beforeAll() {
     System.out.println("**--- JUnit5Sample4Test :: beforeAll :: Executed once before all test methods ---**");
}
 
@BeforeEach
void beforeEach() {
	 System.out.println("**--- JUnit5Sample4Test :: beforeEach :: Executed before each test method ---**");
}

@AfterEach
void afterEach() {
	 System.out.println("**--- JUnit5Sample4Test :: afterEach :: Executed after each test method ---**");
}

@AfterAll
static void afterAll() {
	 System.out.println("**--- JUnit5Sample4Test :: afterAll :: Executed after all test method ---**");
}
 
     @Nested
     class InnerClass {
 
          @BeforeEach
          void beforeEach() {
               System.out.println("**--- InnerClass :: beforeEach :: Executed before each test method ---**");
          }
 
          @AfterEach
          void afterEach() {
        	   System.out.println("**--- InnerClass :: afterEach :: Executed after each test method ---**");
          }
 
          @Test
          void testMethod1() {
        	   System.out.println("**--- InnerClass :: testMethod1 :: Executed test method1 ---**");
          }
 
          @Nested
          class InnerMostClass {
 
               @BeforeEach
               void beforeEach() {
                    System.out.println("**--- InnerMostClass :: beforeEach :: Executed before each test method ---**");
               }
 
               @AfterEach
               void afterEach() {
            	    System.out.println("**--- InnerMostClass :: afterEach :: Executed after each test method ---**");
               }
 
               @Test
               void testMethod2() {
            	    System.out.println("**--- InnerMostClass :: testMethod2 :: Executed test method2 ---**");
               }
        }
    }

JUnit测试异常

在某些情况下，方法有望根据特定条件抛出异常。如果给定的方法未抛出指定的异常，assertThrows 将测试失败。

Throwable exception = assertThrows(IllegalArgumentException.class, () -> {
     throw new IllegalArgumentException("Illegal Argument Exception occured");
});
assertEquals("Illegal Argument Exception occured", exception.getMessage());

JUnit测试执行

单元测试可以通过多种方式来执行，其中两种方式如下：

• Use Eclipse IDE Oxygen.3a (4.7.3a) Release and open test file to be executed. Right-click on the file and choose option Runs As followed by JUnit Test
• Use mvn test command on Windows command prompt

总结

我们已经通过一些例子来探索了JUnit5及其新特性。我们还看了如何使用JUnit注解、断言、假设、异常以及编写嵌套测试类。

您可以从我们的GitHub仓库中下载完整的示例项目。