Connection is not available -H2 DB - when running unit tests in suite

Question

I have a couple of unit tests running with H2 DB in memory. My application is a SpringBoot app. The datasource is spring injected by autowiring. My DB configuration, defined in application.properties, is the following:

spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.url=jdbc:h2:mem:testdb;
spring.datasource.username=sa
spring.datasource.password=
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.H2Dialect

Running the tests, defined eachone in its own class, one by one is successful but when I run a unit tests suit (@RunWith(Suite.class)) after the successful execution of the first 3 it is throwing me an exception:

java.sql.SQLTransientConnectionException: HikariPool-1 - Connection is not available, request timed out after 30005ms.
at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:696)
    at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:197)
    at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:162)
    at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:128)
    at com.cgi.nm.radrat.database.InternetUsageDao.retrieveInternetUsage(InternetUsageDao.java:586)
    at com.cgi.nm.radrat.service.EnsembleService.createPIFile(EnsembleService.java:151)
    at com.cgi.nm.radrat.RadratController.createPIFileForSympatico(RadratController.java:29)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.scheduling.support.ScheduledMethodRunnable.run(ScheduledMethodRunnable.java:84)
    at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
    at org.springframework.scheduling.concurrent.ReschedulingRunnable.run(ReschedulingRunnable.java:95)
    at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)

Any idea? Thank you for your help