Declare JUnit test classes package-private and final

Error Prone now fails the build on Picnic's JUnitClassModifiers, the
first of the checks vfs-s3 makes build-breaking to be switched on here:
a JUnit 5 test class that is not abstract is package-private and final.
Its suggested fix changed the 25 test classes that were public or not
final. None of them is extended or used outside its package.

Author: abashev

buildSrc/src/main/groovy/open-java-format.error-prone-conventions.gradle

@@ -28,26 +28,26 @@ pluginManager.withPlugin('java-gradle-plugin') {
     }
 }
 
-// The checks vfs-s3 makes build-breaking. Off until the code is fixed, one check at a time:
-// JUnitMethodDeclaration 206, StaticImport 84, LexicographicalAnnotationListing 46, JUnitClassModifiers 25,
+// The checks vfs-s3 makes build-breaking. The commented ones stay off until the code is fixed, one check at a
+// time: JUnitMethodDeclaration 206, StaticImport 84, LexicographicalAnnotationListing 46,
 // RedundantStringConversion 6, AlmostJavadoc 3 findings; the rest have none.
-//tasks.withType(JavaCompile).configureEach {
-//    options.errorprone {
-//        error('StaticImport')
-//        error('UnnecessarilyFullyQualified')
-//        error('EmptyBlockTag')
-//        error('OperatorPrecedence')
-//        error('RedundantStringConversion')
-//        error('PatternMatchingInstanceof')
-//        error('UnnecessaryParentheses')
-//        error('LexicographicalAnnotationListing')
-//        error('JUnitMethodDeclaration')
-//        error('JUnitClassModifiers')
-//        error('MissingSummary')
-//        error('AlmostJavadoc')
-//        error('BadImport')
-//        error('JdkObsolete')
-//        // NonStaticImport (Picnic) is the inverse of StaticImport and would give contradictory advice.
-//        disable('NonStaticImport')
-//    }
-//}
+tasks.withType(JavaCompile).configureEach {
+    options.errorprone {
+        //error('StaticImport')
+        //error('UnnecessarilyFullyQualified')
+        //error('EmptyBlockTag')
+        //error('OperatorPrecedence')
+        //error('RedundantStringConversion')
+        //error('PatternMatchingInstanceof')
+        //error('UnnecessaryParentheses')
+        //error('LexicographicalAnnotationListing')
+        //error('JUnitMethodDeclaration')
+        error('JUnitClassModifiers')
+        //error('MissingSummary')
+        //error('AlmostJavadoc')
+        //error('BadImport')
+        //error('JdkObsolete')
+        // NonStaticImport (Picnic) is the inverse of StaticImport and would give contradictory advice.
+        //disable('NonStaticImport')
+    }
+}

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/AppliesWithoutSpotlessTest.java

@@ -28,7 +28,7 @@
  * Most projects that apply the formatter never apply Spotless, so there are no Spotless classes on their buildscript
  * classpath. The Spotless integration has to stay dormant there instead of failing the whole plugin.
  */
-class AppliesWithoutSpotlessTest {
+final class AppliesWithoutSpotlessTest {
 
     @TempDir
     private Path projectDir;

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/ConfigureJavaFormatterXmlTest.java

@@ -33,7 +33,7 @@
 import org.junit.jupiter.params.provider.CsvSource;
 import org.junit.jupiter.params.provider.MethodSource;
 
-class ConfigureJavaFormatterXmlTest {
+final class ConfigureJavaFormatterXmlTest {
 
     @Language("xml")
     private static final String EXISTING_CLASS_PATH = """

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/FormatDiffTest.java

@@ -41,7 +41,7 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.MethodSource;
 
-class FormatDiffTest {
+final class FormatDiffTest {
 
     private static final File CLASSPATH_FILE = new File("build/impl.classpath");
     private static final File NATIVE_IMAGE_FILE = new File("build/nativeImage.path");

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/FormatDiffWithoutJavacExportsTest.java

@@ -30,7 +30,7 @@
  * internals (#19). It fails before the first file now, naming the two settings that make the formatter run. This
  * class runs in the default test task; PalantirJavaFormatPluginTest does not, because it needs the native binary.
  */
-class FormatDiffWithoutJavacExportsTest {
+final class FormatDiffWithoutJavacExportsTest {
 
     /** ./gradlew writeImplClasspath generates this file. Forward slashes: the path goes into a Groovy string. */
     private static final String CLASSPATH_FILE =

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/PalantirJavaFormatIdeaPluginTest.java

@@ -35,7 +35,7 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 
-class PalantirJavaFormatIdeaPluginTest {
+final class PalantirJavaFormatIdeaPluginTest {
 
     // Forward slashes: the path goes into a Groovy string, where a Windows backslash would start an escape.
     private static final String NATIVE_IMAGE_FILE =

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/PalantirJavaFormatPluginTest.java

@@ -26,7 +26,7 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
 
-class PalantirJavaFormatPluginTest {
+final class PalantirJavaFormatPluginTest {
 
     /** ./gradlew writeImplClasspath generates this file. */
     // Forward slashes: the path goes into a Groovy string, where a Windows backslash would start an escape.

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/PalantirJavaFormatSpotlessPluginTest.java

@@ -25,7 +25,7 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
 
-class PalantirJavaFormatSpotlessPluginTest {
+final class PalantirJavaFormatSpotlessPluginTest {
 
     /** ./gradlew writeImplClasspath generates this file. */
     // Forward slashes: the path goes into a Groovy string, where a Windows backslash would start an escape.

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/SpotlessExcludesTest.java

@@ -27,7 +27,7 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 
-class SpotlessExcludesTest {
+final class SpotlessExcludesTest {
 
     // Forward slashes: the path goes into a Groovy string, where a Windows backslash would start an escape.
     private static final String CLASSPATH_FILE =

gradle-open-java-format/src/test/java/com/palantir/javaformat/gradle/SupportsCurrentSpotlessTest.java

@@ -31,7 +31,7 @@
  * cache, which is what now catches eager resolution. gradle-consistent-versions used to play that role; it is gone,
  * because applying it is precisely what Gradle 9 rejects.
  */
-class SupportsCurrentSpotlessTest {
+final class SupportsCurrentSpotlessTest {
 
     // Forward slashes: the path goes into a Groovy string, where a Windows backslash would start an escape.
     private static final String CLASSPATH_FILE =