Question: I am using Eclipse Oxygen.3 Release (4.7.3). The following is my JUnit test class:

```java
import static org.junit.Assert.assertEquals;

import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

class MyMathTest {
    MyMath myMath = new MyMath();

    @Before
    public void before() {
        System.out.println("Before");
    }

    @After
    public void after() {
        System.out.println("After");
    }

    @Test
    public void testSum_with3numbers() {
        System.out.println("Test1");
        int result = myMath.sum(new int[] {1,2,3});
        int expected = 6;
        assertEquals(expected, result);
    }

    @Test
    public void testSum_with1numbers() {
        System.out.println("Test2");
        int result = myMath.sum(new int[] {3});
        int expected = 3;
        assertEquals(expected, result);
    }

    @BeforeClass
    public static void beforeClass() {
        System.out.println("Before class");
    }

    @AfterClass
    public static void afterClass() {
        System.out.println("After class");
    }

}

```

When I run this Junit test, eclipse keeps popping up dialog telling **"No tests found with test runner 'JUnit 5'"**. Why?

[![enter image description here](https://i.stack.imgur.com/p7I9T.png)](https://i.stack.imgur.com/p7I9T.png)

Answer: 
Take a look back to your imports.

You imports `import org.junit.Test;` (Used for run test cases with JUnit 4)

You need to import `import org.junit.jupiter.api.Test;` to run tast case with JUnit5.
I had the same problem with an Eclipse (2020-09) non-Maven project. None of the proposed solutions worked, but changing the compiler from 9.0.4 to 15.0.1 did.

I did that by selecting `Preferences > Java > Installed JREs`and checking the box next to `jdk-15.01`. You may need to install a recent JDK if none are shown.