Issue checkstyle#13809: Kill mutation in Tree-Walker-2

config/pitest-suppressions/pitest-tree-walker-suppressions.xml

@@ -81,12 +81,4 @@
     <lineContent>Comparator.nullsLast(Comparator.naturalOrder()))</lineContent>
   </mutation>
 
-  <mutation unstable="false">
-    <sourceFile>TreeWalker.java</sourceFile>
-    <mutatedClass>com.puppycrawl.tools.checkstyle.TreeWalker</mutatedClass>
-    <mutatedMethod>lambda$createNewCheckSortedSet$3</mutatedMethod>
-    <mutator>org.pitest.mutationtest.engine.gregor.mutators.returns.EmptyObjectReturnValsMutator</mutator>
-    <description>replaced return value with &quot;&quot; for com/puppycrawl/tools/checkstyle/TreeWalker::lambda$createNewCheckSortedSet$3</description>
-    <lineContent>Comparator.&lt;AbstractCheck, String&gt;comparing(check -&gt; check.getClass().getName())</lineContent>
-  </mutation>
 </suppressedMutations>

src/test/java/com/puppycrawl/tools/checkstyle/AbstractModuleTestSupport.java

@@ -481,7 +481,7 @@ private void verifyViolations(Configuration config,
      * @return list of actual violations.
      * @throws Exception if exception occurs during verification process.
      */
-    private List<String> getActualViolationsForFile(Configuration config,
+    protected List<String> getActualViolationsForFile(Configuration config,
                                                     String file) throws Exception {
         stream.flush();
         stream.reset();

src/test/java/com/puppycrawl/tools/checkstyle/TreeWalkerTest.java

@@ -679,6 +679,52 @@ public void testExternalResourceFiltersWithNoExternalResource() throws Exception
         verify(checkerConfig, filePath, expected);
     }
 
+    @Test
+    public void testMultiCheckOfSameType() throws Exception {
+
+        final DefaultConfiguration configuration1 = createModuleConfig(ParameterNameCheck.class);
+        configuration1.addProperty("format", "^[a-z]([a-z0-9][a-zA-Z0-9]*)?$");
+        configuration1.addProperty("accessModifiers", "protected, package, private");
+        configuration1.addProperty("id", "check1");
+        final DefaultConfiguration configuration2 = createModuleConfig(ParameterNameCheck.class);
+        configuration2.addProperty("format", "^[0-1]([a-z0-9][a-zA-Z0-9]*)?$");
+        configuration2.addProperty("accessModifiers", "protected, package, private");
+        configuration2.addProperty("id", "check2");
+        final DefaultConfiguration configuration3 = createModuleConfig(WhitespaceAfterCheck.class);
+        configuration3.addProperty("id", "check3");
+        final DefaultConfiguration configuration4 = createModuleConfig(WhitespaceAroundCheck.class);
+        configuration4.addProperty("id", "check4");
+
+        final DefaultConfiguration treeWalkerConfig = createModuleConfig(TreeWalker.class);
+        treeWalkerConfig.addChild(configuration4);
+        treeWalkerConfig.addChild(configuration3);
+        treeWalkerConfig.addChild(configuration2);
+        treeWalkerConfig.addChild(configuration1);
+
+        final String[] expected = {
+            "5:28: " + getCheckMessage(ParameterNameCheck.class,
+                    "name.invalidPattern", "V2", "^[a-z]([a-z0-9][a-zA-Z0-9]*)?$"),
+            "5:28: " + getCheckMessage(ParameterNameCheck.class,
+                    "name.invalidPattern", "V2", "^[0-1]([a-z0-9][a-zA-Z0-9]*)?$"),
+            "5:32: " + getCheckMessage(WhitespaceAfterCheck.class, "ws.notFollowed", "{"),
+            "5:33: " + getCheckMessage(WhitespaceAroundCheck.class, "ws.notPreceded", "}"),
+            "10:9: " + getCheckMessage(WhitespaceAfterCheck.class, "ws.notFollowed", "if"),
+            "10:9: " + getCheckMessage(WhitespaceAroundCheck.class, "ws.notFollowed", "if"),
+        };
+
+        List<String> violations =
+                getActualViolationsForFile(treeWalkerConfig, getPath("InputTreeWalker2.java"));
+
+        for(int index = 0; index < expected.length - 1; index++) {
+            String expectedViolationMessagePosition = expected[index].substring(0,4);
+            String detectedViolationMessagePosition = violations.get(index).substring(0,4);
+            assertWithMessage("")
+                .that(detectedViolationMessagePosition)
+                .isEqualTo(expectedViolationMessagePosition);
+        }
+
+    }
+
     public static class BadJavaDocCheck extends AbstractCheck {
 
         @Override

src/test/resources/com/puppycrawl/tools/checkstyle/treewalker/InputTreeWalker2.java

@@ -0,0 +1,13 @@
+package com.puppycrawl.tools.checkstyle.treewalker;
+
+public class InputTreeWalker2 {
+//    void fn1(int v1) {}
+    protected void fn2(int V2) {} // violation "Parameter name 'V2' must match pattern"
+//    private void fn3(int a) {}
+
+    public void method() {
+        boolean test = true;
+        if(test) {
+        }
+    }
+}