If none of the other answers work for you, here's what worked for me.

Restart eclipse

I had source folder configured correctly, and unit tests correctly annotated but was still getting "No JUnit tests found", for one project. After a restart it worked. I was using STS 3.6.2 based of eclipse Luna 4.4.1

in first step we must replace @Mock to Spy

and then we must change in when() method to when(spyInstance.method) and then we need called method has spyInstance.method to testing

this is my code after fixed you can see it

@Spy
InMemory inMemoryGet;  // replace it from mock to spy


@InjectMocks
UserService userService;

@Before
public void init(){
    MockitoAnnotations.initMocks(this);
}

@Test
public void registry(){

    UserDto emp = new UserDto(1L,"Lokesh","Gupta",25); // add it

    when(inMemoryGet.save(emp.ToDTO(emp))).thenReturn(emp.ToDTO(emp));
    verify(inMemoryGet, times(0)).save(emp.ToDTO(emp)); // how many time invoke
    userService.registry(emp); // called method from here
    verify(inMemoryGet, times(1)).save(emp.ToDTO(emp));
    System.out.println("\"Test\" = " + "Pass");
}

When we get these errors it seems like Eclipse is just confused. Restart Eclipse, refresh the project, clean it, let Eclipse rebuild it, and try again. Most times that works like a charm.

tl;dr

Add two dependencies to your project:

• JUnit Jupiter (Aggregator)
• Maven Surefire Plugin

<!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter -->
<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <version>5.9.1</version>
    <scope>test</scope>
</dependency>

… and:

<!-- https://maven.apache.org/surefire/maven-surefire-plugin/dependency-info.html -->
<dependency>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.0.0-M7</version>
  <type>maven-plugin</type>
</dependency>

junit-jupiter — the simpler archetype for JUnit 5

The Answer by LaurentG seems to be correct, but a bit outdated.

As of JUnit 5.4, you can replace those multiple Maven artifacts:

• junit
• junit-jupiter-api
• junit-jupiter-engine

…with a single artifact:

• junit-jupiter

…to run JUnit 5 tests.

This artifact is an aggregate of other artifacts, a convenient wrapper to simplify your POM file. See this repository.

<!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter -->
<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter</artifactId>
    <version>5.9.1</version>
    <scope>test</scope>
</dependency>

This gives you all you need to write and run JUnit 5 Jupiter tests.

maven-surefire-plugin

You would also need the Surefire plugin as shown in that other Answer. Be sure to get the latest version, as Surefire has had some important fixes/enhancements recently.

See this list of dependency declarations for Maven, Buildr, Ivy, Grape, Grails, SBT, and Leiningen. To quote the Maven config:

<!-- https://maven.apache.org/surefire/maven-surefire-plugin/dependency-info.html -->
<dependency>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.0.0-M7</version>
  <type>maven-plugin</type>
</dependency>

junit-vintage-engine for JUnit 3 & 4 tests

If you have old JUnit 3 or JUnit 4 legacy tests that you want to continue to run, add another dependency, junit-vintage-engine.

<!-- https://mvnrepository.com/artifact/org.junit.vintage/junit-vintage-engine -->
<dependency>
    <groupId>org.junit.vintage</groupId>
    <artifactId>junit-vintage-engine</artifactId>
    <version>5.9.1</version>
    <scope>test</scope>
</dependency>

You have to do a static import.

import static org.junit.Assert.*;

Add to your build.gradle:

test {
    useJUnitPlatform()
}

Converting the Java project to Maven Project fixed the issue for me. The conversion was done on Eclipse by: Right Click Project -> Configure -> Convert to Maven Project