Eclipse No tests found using JUnit 5 caused by NoClassDefFoundError for LauncherFactory

I fixed the issue by right clicking the test and selecting 'Run Configurations' and changing the "Test runner:" selection to 'JUnit 4' as shown here:

I ran the test again and it worked.

I have the same issue with STS 3.9.1. It seems like an Eclipse bug, however, to fix this you can add a test dependency junit-platform-launcher to your project (https://mvnrepository.com/artifact/org.junit.platform/junit-platform-launcher)

This is how I did for my project which uses gradle:

dependencies {
    // other stuff here

    testCompile group: 'org.junit.jupiter', name: 'junit-jupiter-engine', version: "5.${junit5MinorVersion}"
    testCompile group: 'org.junit.platform', name: 'junit-platform-launcher', version: "1.${junit5MinorVersion}"
}

gradle.properties file:

junit5MinorVersion=1.0

I believe the same applies if you see this exception while using IntelliJ IDEA.

In my case, the problem was myself and no IDE like Eclipse. I've imported the JUnit 4 Test class.

So do NOT import this one:

import org.junit.Test  // JUnit 4

But DO import that one:

import org.junit.jupiter.api.Test // JUnit 5