Issue #3316: use pitest testing of checks.sizes package in shippable CI

pom.xml

@@ -1465,5 +1465,30 @@
       </build>
     </profile>
 
+    <profile>
+      <id>pitest-checks-sizes</id>
+      <build>
+        <plugins>
+          <plugin>
+            <groupId>org.pitest</groupId>
+            <artifactId>pitest-maven</artifactId>
+            <version>1.1.10</version>
+            <configuration>
+              <targetClasses>
+                <param>com.puppycrawl.tools.checkstyle.checks.sizes.*</param>
+              </targetClasses>
+              <targetTests>
+                <param>com.puppycrawl.tools.checkstyle.checks.sizes.*</param>
+              </targetTests>
+              <mutationThreshold>88</mutationThreshold>
+              <timeoutFactor>10</timeoutFactor>
+              <timeoutConstant>50000</timeoutConstant>
+              <threads>4</threads>
+            </configuration>
+          </plugin>
+        </plugins>
+      </build>
+    </profile>
+
   </profiles>
 </project>

shippable.yml

@@ -10,4 +10,4 @@ build:
     - /root/.m2
 
   ci:
-    - mvn clean verify
+    - mvn clean verify -Ppitest-checks-sizes org.pitest:pitest-maven:mutationCoverage