Add: Suppressions config for tests

build.gradle

@@ -46,6 +46,10 @@ test {
 
 checkstyle {
     toolVersion = '10.21.0'
+    configFile = file('config/checkstyle/checkstyle.xml')
+    configProperties = [
+        'suppressionFile': file('config/checkstyle/suppressions.xml').absolutePath
+    ]
 }
 
 tasks.named('jar', Jar) {

config/checkstyle/checkstyle.xml

@@ -12,6 +12,10 @@
     <!-- https://checkstyle.sourceforge.io/config.html#Properties_1 -->
     <property name="fileExtensions" value="java"/>
 
+    <module name="SuppressionFilter">
+        <property name="file" value="${suppressionFile}"/>
+    </module>
+
     <!-- Only allow spaces -->
     <!-- https://checkstyle.sourceforge.io/checks/whitespace/filetabcharacter.html -->
     <module name="FileTabCharacter"/>
@@ -141,9 +145,10 @@
         <!-- Disallow System.out.println -->
         <!-- https://checkstyle.sourceforge.io/checks/regexp/regexp.html -->
         <module name="Regexp">
+            <property name="id" value="SystemOutErr"/>
             <property name="format" value="System\.(out|err)\.print"/>
             <property name="illegalPattern" value="true"/>
-            <property name="message" value="No `System.out.print(err)` in production code — use a logger."/>
+            <property name="message" value="No `System.out.print(err)` allowed — use a logger."/>
         </module>
 
         <!-- Disallow whitespace before semicolon or bracket -->
@@ -159,7 +164,7 @@
         <module name="Regexp">
             <property name="format" value=" +$"/>
             <property name="illegalPattern" value="true"/>
-            <property name="message" value="Kein trailing Whitespace."/>
+            <property name="message" value="No trailing whitespace."/>
         </module>
     </module>
 </module>

config/checkstyle/suppressions.xml

@@ -0,0 +1,24 @@
+<?xml version="1.0"?>
+<!DOCTYPE suppressions PUBLIC
+    "-//Checkstyle//DTD SuppressionFilter Configuration 1.2//EN"
+    "https://checkstyle.org/dtds/suppressions_1_2.dtd">
+
+<suppressions>
+    <!-- Allow literal, for example assertEquals(42, life.answer()) -->
+    <suppress checks="MagicNumber" files=".*Test\.java"/>
+
+    <!-- Allow longer method names as the are usually descriptive of the test -->
+    <suppress checks="MethodLength" files=".*Test\.java"/>
+
+    <!-- Allow methods with more parameters -->
+    <suppress checks="ParameterNumber" files=".*Test\.java"/>
+
+    <!-- Allow for System.out.println in tests -->
+    <suppress id="SystemOutErr" files=".*Test\.java"/>
+
+    <!-- Allow wildcard imports (import x.*)  -->
+    <suppress checks="AvoidStarImport" files=".*Test\.java"/>
+
+    <!-- Allow for compacter line seperators -->
+    <suppress checks="EmptyLineSeparator" files=".*Test\.java"/>
+</suppressions>