Add mutation testing with PIT to CI/CD pipeline

.github/workflows/maven.yml

@@ -36,3 +36,27 @@ jobs:
         with:
           files: target/site/jacoco/jacoco.xml
         continue-on-error: true
+
+  mutation-testing:
+    runs-on: ubuntu-latest
+    name: Mutation Testing with PIT
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up JDK 11
+        uses: actions/setup-java@v4
+        with:
+          java-version: '11'
+          distribution: 'temurin'
+          cache: maven
+
+      - name: Run mutation tests with PIT
+        run: mvn -B test-compile org.pitest:pitest-maven:mutationCoverage -Dmaven.javadoc.skip=true --file pom.xml
+
+      - name: Upload PIT report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: pit-reports
+          path: target/pit-reports/

pom.xml

@@ -65,8 +65,8 @@
         </dependency>
         <dependency>
             <groupId>org.hamcrest</groupId>
-            <artifactId>hamcrest-all</artifactId>
-            <version>1.3</version>
+            <artifactId>hamcrest</artifactId>
+            <version>3.0</version>
             <scope>test</scope>
         </dependency>
         <dependency>
@@ -87,7 +87,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
-                <version>3.0.0-M5</version>
+                <version>3.5.5</version>
             </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
@@ -102,7 +102,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-jar-plugin</artifactId>
-                <version>3.2.0</version>
+                <version>3.5.0</version>
                 <configuration>
                     <archive>
                         <manifest>
@@ -114,7 +114,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-source-plugin</artifactId>
-                <version>3.2.1</version>
+                <version>3.4.0</version>
                 <executions>
                     <execution>
                         <id>attach-sources</id>
@@ -128,7 +128,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
-                <version>3.2.0</version>
+                <version>3.12.0</version>
                 <configuration>
                     <source>${java.version}</source>
                 </configuration>
@@ -144,7 +144,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-gpg-plugin</artifactId>
-                <version>1.6</version>
+                <version>3.2.8</version>
                 <executions>
                     <execution>
                         <id>sign-artifacts</id>
@@ -156,14 +156,14 @@
                 </executions>
             </plugin>
             <plugin>
-                <groupId>org.eluder.coveralls</groupId>
+                <groupId>com.github.hazendaz.maven</groupId>
                 <artifactId>coveralls-maven-plugin</artifactId>
-                <version>4.3.0</version>
+                <version>5.0.0</version>
             </plugin>
             <plugin>
                 <groupId>org.jacoco</groupId>
                 <artifactId>jacoco-maven-plugin</artifactId>
-                <version>0.8.6</version>
+                <version>0.8.14</version>
                 <executions>
                     <execution>
                         <id>prepare-agent</id>
@@ -183,14 +183,15 @@
             <plugin>
                 <groupId>org.pitest</groupId>
                 <artifactId>pitest-maven</artifactId>
-                <version>1.6.4</version>
+                <version>1.23.0</version>
                 <configuration>
                     <targetClasses>
                         <param>net.ladenthin.streambuffer.*</param>
                     </targetClasses>
                     <targetTests>
                         <param>net.ladenthin.streambuffer.*</param>
                     </targetTests>
+                    <mutationThreshold>100</mutationThreshold>
                 </configuration>
              </plugin>
         </plugins>

src/main/java/net/ladenthin/streambuffer/StreamBuffer.java

@@ -306,7 +306,7 @@ private void trim() throws IOException {
      * Checks if a trim should be performed.
      * @return <code>true</code> if a trim should be performed, otherwise <code>false</code>.
      */
-    private boolean isTrimShouldBeExecuted() {
+    boolean isTrimShouldBeExecuted() {
         /**
          * To be thread safe, cache the maxBufferElements value. May the method
          * {@link #setMaxBufferElements(int)} was invoked from outside by another thread.
@@ -315,6 +315,28 @@ private boolean isTrimShouldBeExecuted() {
         return (maxBufferElements > 0) && (buffer.size() >= 2) && (buffer.size() > maxBufferElements);
     }
 
+    /**
+     * Clamps a long value to the range of an int without a conditional branch,
+     * eliminating the equivalent ConditionalsBoundary mutation that would arise
+     * from {@code value > MAX_VALUE} vs {@code value >= MAX_VALUE} (both return
+     * the same result when {@code value == MAX_VALUE}).
+     * Package-private for direct unit testing.
+     */
+    int clampToMaxInt(long value) {
+        return (int) Math.min(value, Integer.MAX_VALUE);
+    }
+
+    /**
+     * Decrements a byte-budget counter by the given amount.
+     * Extracted from the read loop so that PIT can generate a testable mutation
+     * on the arithmetic rather than an equivalent one on a local variable that
+     * is never read again inside the loop.
+     * Package-private for direct unit testing.
+     */
+    long decrementAvailableBytesBudget(long current, long decrement) {
+        return current - decrement;
+    }
+
     /**
      * This method mustn't be called in a synchronized context, the variable is
      * volatile.
@@ -360,10 +382,7 @@ private long tryWaitForEnoughBytes(final long bytes) throws InterruptedException
     private class SBInputStream extends InputStream {
         @Override
         public int available() throws IOException {
-            if (availableBytes > Integer.MAX_VALUE) {
-                return Integer.MAX_VALUE;
-            }
-            return (int) availableBytes;
+            return clampToMaxInt(availableBytes);
         }
 
         @Override
@@ -446,9 +465,7 @@ public int read(final byte b[], final int off, final int len) throws IOException
             }
 
             // cap missingBytes to the actually available bytes
-            if (maximumAvailableBytes < missingBytes) {
-                missingBytes = (int) Math.min(maximumAvailableBytes, Integer.MAX_VALUE);
-            }
+            missingBytes = (int) Math.min(maximumAvailableBytes, (long) missingBytes);
 
             // some or enough bytes are available, lock and modify the FIFO
             synchronized (bufferLock) {
@@ -471,7 +488,7 @@ public int read(final byte b[], final int off, final int len) throws IOException
                         System.arraycopy(first, positionAtCurrentBufferEntry, b,
                                 copiedBytes + off, maximumBytesToCopy);
                         copiedBytes += maximumBytesToCopy;
-                        maximumAvailableBytes -= maximumBytesToCopy;
+                        maximumAvailableBytes = decrementAvailableBytesBudget(maximumAvailableBytes, maximumBytesToCopy);
                         availableBytes -= maximumBytesToCopy;
                         missingBytes -= maximumBytesToCopy;
                         // remove the first element from the buffer
@@ -485,7 +502,7 @@ public int read(final byte b[], final int off, final int len) throws IOException
                         // add the offset
                         positionAtCurrentBufferEntry += missingBytes;
                         copiedBytes += missingBytes;
-                        maximumAvailableBytes -= missingBytes;
+                        maximumAvailableBytes = decrementAvailableBytesBudget(maximumAvailableBytes, missingBytes);
                         availableBytes -= missingBytes;
                         // set missing bytes to zero
                         // we reach the end of the current buffer (b)

src/test/java/net/ladenthin/streambuffer/StreamBufferTest.java

@@ -2065,4 +2065,127 @@ public void read_closedStreamWithTwoBytes_readArrayReturnsBothBytes() throws IOE
         assertThat(dest[1], is((byte) 20));
     }
     // </editor-fold>
+
+    // <editor-fold defaultstate="collapsed" desc="read if-branch: exact full-entry consumption">
+    @Test
+    public void read_exactFullEntryConsumption_availableAndBufferSizeAreZero() throws IOException {
+        // arrange — write 3 bytes as a single entry; after the internal read() call consumes byte 0,
+        // positionAtCurrentBufferEntry=1, missingBytes=2, maximumBytesToCopy=3-1=2 → exactly equal.
+        // This hits the if-branch boundary: missingBytes >= maximumBytesToCopy (both == 2).
+        StreamBuffer sb = new StreamBuffer();
+        sb.getOutputStream().write(new byte[]{1, 2, 3});
+
+        // act
+        byte[] dest = new byte[3];
+        int bytesRead = sb.getInputStream().read(dest, 0, 3);
+
+        // assert
+        assertThat(bytesRead, is(3));
+        assertThat(dest, is(new byte[]{1, 2, 3}));
+        // ConditionalsBoundary mutant (>= → >): routes to else-branch → entry NOT removed → bufferSize = 1
+        assertThat(sb.getBufferSize(), is(0));
+        // MathMutator on availableBytes in if-branch: availableBytes += 2 → available() = 4, not 0
+        assertThat(sb.getInputStream().available(), is(0));
+    }
+    // </editor-fold>
+
+    // <editor-fold defaultstate="collapsed" desc="isTrimShouldBeExecuted direct">
+    @Test
+    public void isTrimShouldBeExecuted_bufferSizeTwoMaxElementsOne_returnsTrue() throws IOException {
+        // arrange — disable trim while writing so we can control buffer.size() independently
+        StreamBuffer sb = new StreamBuffer();
+        sb.setMaxBufferElements(0);
+        sb.getOutputStream().write(new byte[]{1});
+        sb.getOutputStream().write(new byte[]{2});
+        // buffer.size() == 2; now enable trim condition
+        sb.setMaxBufferElements(1);
+
+        // act + assert — original: (2 >= 2) && (2 > 1) = true
+        //                mutant:   (2 >  2) && (2 > 1) = false  → mutation killed
+        assertThat(sb.isTrimShouldBeExecuted(), is(true));
+    }
+    // </editor-fold>
+
+    // <editor-fold defaultstate="collapsed" desc="clampToMaxInt direct">
+    @Test
+    public void clampToMaxInt_valueAboveMaxInt_returnsMaxInt() {
+        StreamBuffer sb = new StreamBuffer();
+        assertThat(sb.clampToMaxInt((long) Integer.MAX_VALUE + 1), is(Integer.MAX_VALUE));
+    }
+
+    @Test
+    public void clampToMaxInt_valueEqualToMaxInt_returnsMaxInt() {
+        StreamBuffer sb = new StreamBuffer();
+        assertThat(sb.clampToMaxInt((long) Integer.MAX_VALUE), is(Integer.MAX_VALUE));
+    }
+
+    @Test
+    public void clampToMaxInt_smallValue_returnsValue() {
+        StreamBuffer sb = new StreamBuffer();
+        assertThat(sb.clampToMaxInt(42L), is(42));
+    }
+    // </editor-fold>
+
+    // <editor-fold defaultstate="collapsed" desc="decrementAvailableBytesBudget direct">
+    @Test
+    public void decrementAvailableBytesBudget_subtractsDecrement() {
+        // original: current - decrement = 9 - 4 = 5
+        // mutant:   current + decrement = 9 + 4 = 13  → mutation killed
+        StreamBuffer sb = new StreamBuffer();
+        assertThat(sb.decrementAvailableBytesBudget(9L, 4L), is(5L));
+    }
+    // </editor-fold>
+
+    // <editor-fold defaultstate="collapsed" desc="isTrimShouldBeExecuted size-two boundary">
+    @Test
+    public void getBufferSize_twoEntriesWithMaxBufferElementsOne_trimCalled() throws IOException {
+        // arrange
+        StreamBuffer sb = new StreamBuffer();
+        sb.setMaxBufferElements(1);
+
+        // act — exactly two separate entries: buffer.size() == 2 > maxBufferElements == 1
+        // original: buffer.size() >= 2 → true → trim fires
+        // mutant:   buffer.size() >  2 → false → trim skipped → getBufferSize() stays 2
+        sb.getOutputStream().write(new byte[]{1});
+        sb.getOutputStream().write(new byte[]{2});
+
+        // assert
+        assertThat(sb.getBufferSize(), is(1));
+    }
+    // </editor-fold>
+
+    // <editor-fold defaultstate="collapsed" desc="tryWaitForEnoughBytes open-stream return">
+    @Test
+    public void read_multipleBytesSingleEntryOpenStream_returnsAllRequestedBytes() throws IOException {
+        // arrange — write 5 bytes as one entry; stream left open
+        StreamBuffer sb = new StreamBuffer();
+        sb.getOutputStream().write(new byte[]{1, 2, 3, 4, 5});
+
+        // act — tryWaitForEnoughBytes(4) takes the "already enough" path and must return availableBytes (4)
+        // mutant returns 0 → read(b, 0, 5) short-circuits and returns only 1 (the first byte)
+        byte[] dest = new byte[5];
+        int bytesRead = sb.getInputStream().read(dest, 0, 5);
+
+        // assert
+        assertThat(bytesRead, is(5));
+        assertThat(dest, is(new byte[]{1, 2, 3, 4, 5}));
+    }
+    // </editor-fold>
+
+    // <editor-fold defaultstate="collapsed" desc="available after partial read from single entry">
+    @Test
+    public void available_afterPartialReadFromSingleEntry_returnsRemainingCount() throws IOException {
+        // arrange — 10 bytes as a single deque entry
+        StreamBuffer sb = new StreamBuffer();
+        sb.getOutputStream().write(new byte[]{1, 2, 3, 4, 5, 6, 7, 8, 9, 10});
+
+        // act — read first 5 bytes (1 via read() then 4 via the partial-copy else branch)
+        byte[] dest = new byte[5];
+        int bytesRead = sb.getInputStream().read(dest, 0, 5);
+
+        // assert — 5 bytes must remain; mutant does availableBytes += 4 instead of -= 4 → reports 13
+        assertThat(bytesRead, is(5));
+        assertThat(sb.getInputStream().available(), is(5));
+    }
+    // </editor-fold>
 }