running tests in a maven multi module project

I have a maven multi project with this pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>booking</groupId>
    <artifactId>booking</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <!-- sub modules -->
    <modules>
        <module>b1</module>
        <module>b5</module>
        <module>l1</module>
        <module>l20</module>
    </modules>


</project>

but when I run the tests in the root maven I got this result: No tests to run.

public class CalculationFunctionImplTest {

    @Test
    public void test() {

        CalculationFunctionImpl calculationFunctionImpl = new CalculationFunctionImpl ("time");
        System.out.println(calculationFunctionImpl.calculate());


    }

}