[SUREFIRE-1918] Parallel execution doesn't work with junit-vintage-engine

**[Martin Schneider](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=martinschneider)** opened **[SUREFIRE-1918](https://issues.apache.org/jira/browse/SUREFIRE-1918?redirect=false)** and commented

Tests don't get executed in parallel with JUnit's vintage engine.

The following configuration executes them serially:

```java

 org.junit.vintage
 junit-vintage-engine
 5.7.2

...

 org.apache.maven.plugins
  maven-surefire-plugin
 3.0.0-M5
 
   methods
   true
 

```

 

Replacing the vintage engine with Junit 4 executes tests in parallel as expected:

```java

 junit
 junit
 4.13.2

```

 

I have attached a minimal failing example. `mvn test` will produce the following output:

```java
[INFO] -------------------------------------------------------
[INFO] T E S T S
[INFO] -------------------------------------------------------
[INFO] Running ParallelTest
Test 1 running in main
Test 2 running in main
Test 3 running in main
Test 4 running in main
```

The expected output (and what I get with JUnit 4) would be:

```java
[INFO] -------------------------------------------------------
[INFO] T E S T S
[INFO] -------------------------------------------------------
[INFO] Running ParallelTest
Test 1 running in pool-2-thread-1
Test 3 running in pool-2-thread-3
Test 4 running in pool-2-thread-4
Test 2 running in pool-2-thread-2
```

---

**Affects:** 2.22.2, 3.0.0-M5

**Attachments:**
- [parallel-tests.tar.gz](https://issues.apache.org/jira/secure/attachment/13026447/parallel-tests.tar.gz) (_1015 bytes_)

Start by unpacking parallel-tests.tar.gz and running mvn test with junit-vintage-engine and the shown maven-surefire-plugin configuration. Compare the execution threads with the JUnit 4 variant, then trace how parallel execution is handled for the vintage engine. Done means the vintage configuration runs tests in parallel as shown by the expected output.

Written by the indexing model from the issue text.