How to run test verification when `mvn test` fails?

I’m trying to generate tests for some class in Apache Accumulo and I get a test verification problem:

Running verification command, this can take a couple of minutes..
During test validation the whole suite didn't execute successfully.
This can be caused by pre-existing non-compiling or non-passing tests.
Dcover was unable to determine if the failures are due to an interaction with the existing tests or due to another unknown cause. All modified files have been restored to the state prior to test generation.
The additional files affected by this action are listed below.
/home/drzero/devel/accumulo/shell/src/test/java/org/apache/accumulo/shell/commands/ConstraintCommandDiffblueTest.java
Running verification command, this can take a couple of minutes..

Despite restoring all the generated files to their previous states the test validation didn't succeed.
Please ensure that the verification command "mvn test -pl shell" is successful before running dcover again.
See the log for more details including the output of the verification command.

Alternatively, you can specify the "--skip-test-verification" option to skip these checks.
You can also specify a custom command with the "--verification-command" option.
More detailed information about these options is available via "--help".
Test verification was able to verify 0 out of 4 tests, the remainder were discarded

This is what I did:

git clone https://github.com/apache/accumulo
cd accumulo
git checkout cfd8d44
mvn package -DskipTests # needs Java 11
cd shell
dcover create org.apache.accumulo.shell.commands.ConstraintCommand --verbose

Cover rightly points out that running mvn test inside the shell/ module fails. But then, how can I generate tests and still verify them?