JUnit 5 = JUnit平台+ JUnit Jupiter + JUnit版本。

请参阅：Junit 5文档
如果你通过依赖最新的spring-boot-starter-test来导入junit-jupiter，它将只运行Junit 5风格的测试用例。所以Junit提供了junit-vintage来运行旧的Junit 3/Junit 4用例，默认情况下它不包含在spring-boot-starter-test依赖项中。所以有两个解决方案来保持Junit 4的运行：
1.依赖于junit-jupiter和junit-vintage来支持所有junit 3/4/5的情况。

<dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-test</artifactId>
     <scope>test</scope>
 </dependency>
 <dependency>
     <groupId>org.junit.vintage</groupId>
     <artifactId>junit-vintage-engine</artifactId>
     <scope>test</scope>
 </dependency>

1.从spring-boot-starter-test中排除junit-jupiter以运行Junit 4

<dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-test</artifactId>
     <scope>test</scope>
     <exclusions>
         <exclusion>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter</artifactId>
         </exclusion>
     </exclusions>
 </dependency>

从spring-boot-starter-test依赖项中排除junit-jupiter-engine和junit-vintage-engine，然后在pom中添加JUnit 4依赖项：

<groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
    <exclusions>
        <exclusion>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-engine</artifactId>
        </exclusion>
        <exclusion>
            <groupId>org.junit.vintage</groupId>
            <artifactId>junit-vintage-engine</artifactId>
        </exclusion>
    </exclusions>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
    <scope>test</scope>
</dependency>

我认为您应该迁移到JUnit 5。

从SpringBoot V2.2开始，Spring默认只支持JUnit 5，并删除了与JUnit 4的向后兼容性。在Spring 2.2发行说明中明确指出：https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.2-Release-Notes
“您不能使用junit-vintage-engine，并且需要显式回滚到JUnit 4：“

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>org.junit.jupiter</groupId>
                <artifactId>junit-jupiter</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.junit.vintage</groupId>
                <artifactId>junit-vintage-engine</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.mockito</groupId>
                <artifactId>mockito-junit-jupiter</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
</dependencies>

Springboot 2.4发行说明提到了POM依赖项的更改：

<dependency>
    <groupId>org.junit.vintage</groupId>
    <artifactId>junit-vintage-engine</artifactId>
    <scope>test</scope>
    <exclusions>
        <exclusion>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-core</artifactId>
        </exclusion>
    </exclusions>
</dependency>

https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.4-Release-Notes#junit-5s-vintage-engine-removed-from-spring-boot-starter-test