junit test cases not executing when spring boot application migrated from 2.1.5 to 2.4 - spring-boot

Question

I had an application running in spring-boot 2.1.5, migrated that to version 2.4.0. None of my tests are executing now.
When I hit mvn clean test it always says 0 tests executed.
I noticed that spring boot 2.4.0 comes bundled with junit.jupiter library. My 2.1.5 tests are using junit:junit:4.4 dependency.
How to retain my old test cases without migrating to junit.jupiter?

Answer 1

This is covered in the release notes for Spring Boot 2.4:
If you do not want to migrate your tests to JUnit 5 and wish to continue using JUnit 4, add a dependency on the Vintage Engine, as shown in the following example for Maven:
<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>
If you are using Gradle, the equivalent configuration is shown in the following example:
testImplementation("org.junit.vintage:junit-vintage-engine") {
exclude group: "org.hamcrest", module: "hamcrest-core"
}