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test: add pitest mutation testing and kill survivors
Add an opt-in `pitest` profile (mirrors vortex-java): common PIT setup in the parent pom's pluginManagement, the zstd module names its targetClasses. PIT minions get --enable-native-access so they can drive the native library. Run: ./mvnw -pl zstd -P pitest verify Raise mutation test strength 76% -> 84% with targeted unit tests: - zero-copy heap-segment rejection for the dictionary compress/decompress overloads and the previously-uncovered dst/src sides - fluent return-self contract for reset / loadDictionary / refDictionary - cached-level semantics of reset across the legacy dictionary path - ZstdFrame: sane blockSizeMax mask, truncated-header rejection, dictId and header through the segment overloads, garbage/standard frame negatives - pin Zstd.defaultCompressionLevel() to 3 Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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‎pom.xml‎

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@@ -58,6 +58,8 @@
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<maven-release-plugin.version>3.3.1</maven-release-plugin.version>
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<maven-jar-plugin.version>3.4.2</maven-jar-plugin.version>
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<jacoco-maven-plugin.version>0.8.15</jacoco-maven-plugin.version>
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<pitest-maven.version>1.25.5</pitest-maven.version>
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<pitest-junit5-plugin.version>1.2.3</pitest-junit5-plugin.version>
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<!-- SonarCloud analysis (.github/workflows/sonar.yml). -->
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<sonar.host.url>https://sonarcloud.io</sonar.host.url>
@@ -408,5 +410,49 @@
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</plugins>
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</build>
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</profile>
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<!-- Mutation testing (opt-in: -P pitest). Common PIT setup lives here once; the
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zstd module's own `pitest` profile only adds the plugin to <plugins> and names
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its <targetClasses>. PIT forks minion JVMs that exercise the native library, so
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they get the same enable-native-access flag as surefire. -->
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<profile>
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<id>pitest</id>
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<build>
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<pluginManagement>
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<plugins>
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<plugin>
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<groupId>org.pitest</groupId>
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<artifactId>pitest-maven</artifactId>
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<version>${pitest-maven.version}</version>
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<dependencies>
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<dependency>
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<groupId>org.pitest</groupId>
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<artifactId>pitest-junit5-plugin</artifactId>
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<version>${pitest-junit5-plugin.version}</version>
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</dependency>
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</dependencies>
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<executions>
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<execution>
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<id>pit-report</id>
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<phase>verify</phase>
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<goals>
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<goal>mutationCoverage</goal>
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</goals>
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</execution>
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</executions>
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<configuration>
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<jvmArgs>
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<param>--enable-native-access=ALL-UNNAMED</param>
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</jvmArgs>
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<outputFormats>
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<param>HTML</param>
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<param>XML</param>
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</outputFormats>
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<timestampedReports>false</timestampedReports>
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</configuration>
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</plugin>
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</plugins>
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</pluginManagement>
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</build>
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</profile>
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</profiles>
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</project>

‎zstd/pom.xml‎

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@@ -116,5 +116,24 @@
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</dependency>
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</dependencies>
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</profile>
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<!-- Mutation testing (opt-in): ./mvnw -pl zstd -P pitest verify
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Common PIT setup is inherited from the parent `pitest` profile; this only
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names the scope. Report: zstd/target/pit-reports/. -->
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<profile>
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<id>pitest</id>
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<build>
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<plugins>
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<plugin>
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<groupId>org.pitest</groupId>
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<artifactId>pitest-maven</artifactId>
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<configuration>
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<targetClasses>
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<param>io.github.dfa1.zstd.*</param>
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</targetClasses>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</profile>
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</profiles>
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</project>

‎zstd/src/test/java/io/github/dfa1/zstd/ZstdDictionaryTest.java‎

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@@ -482,6 +482,38 @@ void nullNativeSegmentClearsTheLoadedDictionary() {
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assertThat(cleared).isEqualTo(noDict);
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}
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@Test
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void loadAndRefReturnTheSameCompressContext() {
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// Given a compress context and dictionaries to load and reference
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try (Arena arena = Arena.ofConfined();
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ZstdCompressCtx cctx = new ZstdCompressCtx();
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ZstdCompressDict cdict = new ZstdCompressDict(sut, 19)) {
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// Then every sticky-dictionary call returns the same context, for chaining
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assertThat(cctx.loadDictionary(sut)).isSameAs(cctx);
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assertThat(cctx.loadDictionary(nativeDict(arena, sut.toByteArray()))).isSameAs(cctx);
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assertThat(cctx.loadDictionary((ZstdDictionary) null)).isSameAs(cctx);
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assertThat(cctx.refDictionary(cdict)).isSameAs(cctx);
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assertThat(cctx.refDictionary(null)).isSameAs(cctx);
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}
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}
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@Test
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void loadAndRefReturnTheSameDecompressContext() {
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// Given a decompress context and dictionaries to load and reference
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try (Arena arena = Arena.ofConfined();
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ZstdDecompressCtx dctx = new ZstdDecompressCtx();
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ZstdDecompressDict ddict = new ZstdDecompressDict(sut)) {
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// Then every sticky-dictionary call returns the same context, for chaining
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assertThat(dctx.loadDictionary(sut)).isSameAs(dctx);
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assertThat(dctx.loadDictionary(nativeDict(arena, sut.toByteArray()))).isSameAs(dctx);
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assertThat(dctx.loadDictionary((ZstdDictionary) null)).isSameAs(dctx);
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assertThat(dctx.refDictionary(ddict)).isSameAs(dctx);
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assertThat(dctx.refDictionary(null)).isSameAs(dctx);
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}
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}
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private MemorySegment nativeDict(Arena arena, byte[] raw) {
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MemorySegment seg = arena.allocate(raw.length);
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MemorySegment.copy(raw, 0, seg, ValueLayout.JAVA_BYTE, 0, raw.length);

‎zstd/src/test/java/io/github/dfa1/zstd/ZstdFrameTest.java‎

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@@ -9,6 +9,7 @@
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import java.lang.foreign.MemorySegment;
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import java.nio.charset.StandardCharsets;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import static org.assertj.core.api.Assertions.assertThat;
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}
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assertThat(ZstdFrame.header(frame).hasChecksum()).isTrue();
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}
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@Test
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void reportsASaneBlockSizeMax() {
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// Given a default frame
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ZstdFrameHeader header = ZstdFrame.header(Zstd.compress(PAYLOAD));
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// Then blockSizeMax is the masked 32-bit field — a real block size, never
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// the all-ones value a sign-extension or wrong mask would produce
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assertThat(header.blockSizeMax()).isPositive().isLessThanOrEqualTo(128 * 1024L);
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}
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@Test
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void rejectsATruncatedHeader() {
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// Given the first two bytes of a frame — too short to hold a header
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byte[] truncated = Arrays.copyOf(Zstd.compress(PAYLOAD), 2);
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// When its header is parsed
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ThrowingCallable result = () -> ZstdFrame.header(truncated);
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// Then it fails instead of returning a bogus header
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assertThatThrownBy(result).isInstanceOf(ZstdException.class);
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}
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}
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@Nested
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assertThat(ZstdFrame.dictId(frame)).isEqualTo(dict.id());
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}
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@Test
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void matchesThroughTheSegmentOverload() {
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// Given a dictionary frame in a native segment
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ZstdDictionary dict = trainDict();
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byte[] frame;
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try (ZstdCompressCtx ctx = new ZstdCompressCtx()) {
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frame = ctx.compress(PAYLOAD, dict);
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}
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try (Arena arena = Arena.ofConfined()) {
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MemorySegment seg = Zstd.copyIn(arena, frame);
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// Then the segment overload reports the same non-zero id
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assertThat(ZstdFrame.dictId(seg)).isNotZero().isEqualTo(dict.id());
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}
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}
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private ZstdDictionary trainDict() {
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List<byte[]> samples = new ArrayList<>();
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for (int i = 0; i < 3000; i++) {
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assertThat(ZstdFrame.isSkippableFrame(seg)).isTrue();
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}
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}
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@Test
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void headerThroughTheSegmentOverloadMatchesTheByteArrayForm() {
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// Given a frame in a native segment
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byte[] frame = Zstd.compress(PAYLOAD);
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try (Arena arena = Arena.ofConfined()) {
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MemorySegment seg = Zstd.copyIn(arena, frame);
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// Then the parsed header equals the one from the byte[] overload
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assertThat(ZstdFrame.header(seg)).isEqualTo(ZstdFrame.header(frame));
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}
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}
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@Test
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void garbageNativeSegmentIsNotAFrame() {
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// Given non-frame bytes in a native segment
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try (Arena arena = Arena.ofConfined()) {
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MemorySegment seg = Zstd.copyIn(arena, "not a frame".getBytes(StandardCharsets.UTF_8));
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// Then the segment overload rejects it
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assertThat(ZstdFrame.isZstdFrame(seg)).isFalse();
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}
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}
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@Test
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void standardNativeFrameIsNotSkippable() {
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// Given a standard frame in a native segment
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try (Arena arena = Arena.ofConfined()) {
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MemorySegment seg = Zstd.copyIn(arena, Zstd.compress(PAYLOAD));
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// Then the segment overload reports it is not skippable
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assertThat(ZstdFrame.isSkippableFrame(seg)).isFalse();
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}
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}
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}
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}

‎zstd/src/test/java/io/github/dfa1/zstd/ZstdParameterTest.java‎

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@@ -216,6 +216,59 @@ void decompressContextStillDecodesAfterReset() {
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}
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}
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@Test
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void resetReturnsTheSameContext() {
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// Given both contexts
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try (ZstdCompressCtx cctx = new ZstdCompressCtx();
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ZstdDecompressCtx dctx = new ZstdDecompressCtx()) {
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// Then reset returns the same instance, for chaining
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assertThat(cctx.reset(ZstdResetDirective.SESSION_ONLY)).isSameAs(cctx);
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assertThat(dctx.reset(ZstdResetDirective.SESSION_ONLY)).isSameAs(dctx);
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}
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}
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@Test
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void sessionOnlyKeepsTheCachedLevelForTheLegacyDictionaryPath() {
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// Given a level-19 context reset for the session only, then compressing
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// against a dictionary — the legacy path that reads the cached level field
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ZstdDictionary dict =
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ZstdDictionary.of("dictionary sample payload ".repeat(64).getBytes(StandardCharsets.UTF_8));
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byte[] afterSessionReset;
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try (ZstdCompressCtx sut = new ZstdCompressCtx().level(19)) {
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sut.compress(PAYLOAD, dict);
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sut.reset(ZstdResetDirective.SESSION_ONLY);
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afterSessionReset = sut.compress(PAYLOAD, dict);
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}
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byte[] freshLevel19;
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try (ZstdCompressCtx ctx = new ZstdCompressCtx().level(19)) {
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freshLevel19 = ctx.compress(PAYLOAD, dict);
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}
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// Then the cached level survives the session-only reset
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assertThat(afterSessionReset).isEqualTo(freshLevel19);
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}
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@Test
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void parameterResetClearsTheCachedLevelForTheLegacyDictionaryPath() {
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// Given a level-19 context with parameters reset, then compressing against
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// a dictionary via the legacy path that reads the cached level field
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ZstdDictionary dict =
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ZstdDictionary.of("dictionary sample payload ".repeat(64).getBytes(StandardCharsets.UTF_8));
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byte[] afterParameterReset;
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try (ZstdCompressCtx sut = new ZstdCompressCtx().level(19)) {
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sut.compress(PAYLOAD, dict);
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sut.reset(ZstdResetDirective.PARAMETERS);
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afterParameterReset = sut.compress(PAYLOAD, dict);
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}
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byte[] freshDefaultLevel;
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try (ZstdCompressCtx ctx = new ZstdCompressCtx()) {
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freshDefaultLevel = ctx.compress(PAYLOAD, dict);
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}
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// Then the cached level fell back to the default
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assertThat(afterParameterReset).isEqualTo(freshDefaultLevel);
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}
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@Test
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void rejectsNullDirective() {
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// Given a compression context

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