src/test/settings-mirror-wildcard.xml

<?xml version="1.0"?>

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
  <mirrors>
    <mirror>
      <id>mirror-b</id>
      <url>file:./src/test/repo</url>
      <mirrorOf>*</mirrorOf>
    </mirror>
  </mirrors>
</settings>