Fizzy apply (#125)

* add applyFuzzyTo and restoreFuzzy

* implement applyFuzzyTo and restoreFuzzy for EqualDelta

* add verifyChunk with fuzzy and delta

* implement fuzzy apply and add tests

* fix style

* extract method

* fix: assign lastPatchDelta and lastPatchEnd

* fix use explict import

* document EqualDelta#applyFuzzyToAt

* set access modifiers

* change test method name

* document empty method

* apply from first

* add more tests

* add more documentation about fuzz parameter

* fix documentation about fizzy patch

Co-authored-by: cowwoc <cowwoc2020@gmail.com>

Co-authored-by: cowwoc <cowwoc2020@gmail.com>

java-diff-utils/src/main/java/com/github/difflib/patch/AbstractDelta.java

@@ -70,6 +70,19 @@ public abstract class AbstractDelta<T> implements Serializable {
     
     protected abstract void restore(List<T> target);
     
+    /**
+     * Apply patch fuzzy.
+     *
+     * @param target the list this patch will be applied to
+     * @param fuzz the number of elements to ignore before/after the patched elements
+     * @param position the position this patch will be applied to. ignores {@code source.getPosition()}
+     * @see <a href="https://www.gnu.org/software/diffutils/manual/html_node/Inexact.html">Description of Fuzzy Patch</a> for more information.
+     */
+    @SuppressWarnings("RedundantThrows")
+    protected void applyFuzzyToAt(List<T> target, int fuzz, int position) throws PatchFailedException {
+        throw new UnsupportedOperationException(this.getClass().getSimpleName() + " does not supports applying patch fuzzy");
+    }
+
     /**
      * Create a new delta of the actual instance with customized chunk data.
      */

java-diff-utils/src/main/java/com/github/difflib/patch/ChangeDelta.java

@@ -66,6 +66,19 @@ public final class ChangeDelta<T> extends AbstractDelta<T> {
         }
     }
 
+    protected void applyFuzzyToAt(List<T> target, int fuzz, int position) throws PatchFailedException {
+        int size = getSource().size();
+        for (int i = fuzz; i < size - fuzz; i++) {
+            target.remove(position + fuzz);
+        }
+
+        int i = fuzz;
+        for (T line : getTarget().getLines().subList(fuzz, getTarget().size() - fuzz)) {
+            target.add(position + i, line);
+            i++;
+        }
+    }
+
     @Override
     public String toString() {
         return "[ChangeDelta, position: " + getSource().getPosition() + ", lines: "

java-diff-utils/src/main/java/com/github/difflib/patch/Chunk.java

@@ -95,10 +95,28 @@ public final class Chunk<T> implements Serializable {
      * @throws com.github.difflib.patch.PatchFailedException
      */
     public VerifyChunk verifyChunk(List<T> target) throws PatchFailedException {
-        if (position > target.size() || last() > target.size()) {
+        return verifyChunk(target, 0, getPosition());
+    }
+
+    /**
+     * Verifies that this chunk's saved text matches the corresponding text in
+     * the given sequence.
+     *
+     * @param target the sequence to verify against.
+     * @param fuzz the count of ignored prefix/suffix
+     * @param position the position of target
+     * @throws com.github.difflib.patch.PatchFailedException
+     */
+    public VerifyChunk verifyChunk(List<T> target, int fuzz, int position) throws PatchFailedException {
+        //noinspection UnnecessaryLocalVariable
+        int startIndex = fuzz;
+        int lastIndex = size() - fuzz;
+        int last = position + size() - 1;
+
+        if (position + fuzz > target.size() || last - fuzz > target.size()) {
             return VerifyChunk.POSITION_OUT_OF_TARGET;
         }
-        for (int i = 0; i < size(); i++) {
+        for (int i = startIndex; i < lastIndex; i++) {
             if (!target.get(position + i).equals(lines.get(i))) {
                 return VerifyChunk.CONTENT_DOES_NOT_MATCH_TARGET;
             }

java-diff-utils/src/main/java/com/github/difflib/patch/EqualDelta.java

@@ -35,6 +35,14 @@ public class EqualDelta<T> extends AbstractDelta<T> {
     protected void restore(List<T> target) {
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    protected void applyFuzzyToAt(List<T> target, int fuzz, int delta) {
+        // equals so no operations
+    }
+
     @Override
     public String toString() {
         return "[EqualDelta, position: " + getSource().getPosition() + ", lines: "

java-diff-utils/src/main/java/com/github/difflib/patch/Patch.java

@@ -66,6 +66,117 @@ public final class Patch<T> implements Serializable {
         return result;
     }
 
+    private static class PatchApplyingContext<T> {
+        public final List<T> result;
+        public final int maxFuzz;
+
+        // the position last patch applied to.
+        public int lastPatchEnd = -1;
+
+        ///// passing values from find to apply
+        public int currentFuzz = 0;
+
+        public int defaultPosition;
+        public boolean beforeOutRange = false;
+        public boolean afterOutRange = false;
+
+        private PatchApplyingContext(List<T> result, int maxFuzz) {
+            this.result = result;
+            this.maxFuzz = maxFuzz;
+        }
+    }
+
+    public List<T> applyFuzzy(List<T> target, int maxFuzz) throws PatchFailedException {
+        PatchApplyingContext<T> ctx = new PatchApplyingContext<>(new ArrayList<>(target), maxFuzz);
+
+        // the difference between patch's position and actually applied position
+        int lastPatchDelta = 0;
+
+        for (AbstractDelta<T> delta : getDeltas()) {
+            ctx.defaultPosition = delta.getSource().getPosition() + lastPatchDelta;
+            int patchPosition = findPositionFuzzy(ctx, delta);
+            if (0 <= patchPosition) {
+                delta.applyFuzzyToAt(ctx.result, ctx.currentFuzz, patchPosition);
+                lastPatchDelta = patchPosition - delta.getSource().getPosition();
+                ctx.lastPatchEnd = delta.getSource().last() + lastPatchDelta;
+            } else {
+                conflictOutput.processConflict(VerifyChunk.CONTENT_DOES_NOT_MATCH_TARGET, delta, ctx.result);
+            }
+        }
+
+        return ctx.result;
+    }
+
+    // negative for not found
+    private int findPositionFuzzy(PatchApplyingContext<T> ctx, AbstractDelta<T> delta) throws PatchFailedException {
+        for (int fuzz = 0; fuzz <= ctx.maxFuzz; fuzz++) {
+            ctx.currentFuzz = fuzz;
+            int foundPosition = findPositionWithFuzz(ctx, delta, fuzz);
+            if (foundPosition >= 0) {
+                return foundPosition;
+            }
+        }
+        return -1;
+    }
+
+    // negative for not found
+    private int findPositionWithFuzz(PatchApplyingContext<T> ctx, AbstractDelta<T> delta, int fuzz) throws PatchFailedException {
+        if (delta.getSource().verifyChunk(ctx.result, fuzz, ctx.defaultPosition) == VerifyChunk.OK) {
+            return ctx.defaultPosition;
+        }
+
+        ctx.beforeOutRange = false;
+        ctx.afterOutRange = false;
+
+        // moreDelta >= 0: just for overflow guard, not a normal condition
+        //noinspection OverflowingLoopIndex
+        for (int moreDelta = 0; moreDelta >= 0; moreDelta++) {
+            int pos = findPositionWithFuzzAndMoreDelta(ctx, delta, fuzz, moreDelta);
+            if (pos >= 0) {
+                return pos;
+            }
+            if (ctx.beforeOutRange && ctx.afterOutRange) {
+                break;
+            }
+        }
+
+        return -1;
+    }
+
+    // negative for not found
+    private int findPositionWithFuzzAndMoreDelta(PatchApplyingContext<T> ctx, AbstractDelta<T> delta, int fuzz, int moreDelta) throws PatchFailedException {
+        // range check: can't apply before end of last patch
+        if (!ctx.beforeOutRange) {
+            int beginAt = ctx.defaultPosition - moreDelta + fuzz;
+            // We can't apply patch before end of last patch.
+            if (beginAt <= ctx.lastPatchEnd) {
+                ctx.beforeOutRange = true;
+            }
+        }
+        // range check: can't apply after end of result
+        if (!ctx.afterOutRange) {
+            int beginAt = ctx.defaultPosition + moreDelta + delta.getSource().size() - fuzz;
+            // We can't apply patch before end of last patch.
+            if (ctx.result.size() < beginAt) {
+                ctx.afterOutRange = true;
+            }
+        }
+
+        if (!ctx.beforeOutRange) {
+            VerifyChunk before = delta.getSource().verifyChunk(ctx.result, fuzz, ctx.defaultPosition - moreDelta);
+            if (before == VerifyChunk.OK) {
+                return ctx.defaultPosition - moreDelta;
+            }
+        }
+        if (!ctx.afterOutRange) {
+            VerifyChunk after = delta.getSource().verifyChunk(ctx.result, fuzz, ctx.defaultPosition + moreDelta);
+            if (after == VerifyChunk.OK) {
+                return ctx.defaultPosition + moreDelta;
+            }
+        }
+        return -1;
+    }
+
     /**
      * Standard Patch behaviour to throw an exception for pathching conflicts.
      */

java-diff-utils/src/test/java/com/github/difflib/algorithm/myers/WithMeyersDiffWithLinearSpacePatchTest.java

@@ -2,6 +2,7 @@ package com.github.difflib.algorithm.myers;
 
 import com.github.difflib.patch.*;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.fail;
 
 import java.io.ByteArrayInputStream;
@@ -9,8 +10,13 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
+import java.util.Comparator;
 import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 
 import org.junit.jupiter.api.Test;
 
@@ -57,6 +63,104 @@ public class WithMeyersDiffWithLinearSpacePatchTest {
         }
     }
 
+    // region testPatch_fuzzyApply utils
+
+    private List<String> intRange(int count) {
+        return IntStream.range(0, count)
+                .mapToObj(Integer::toString)
+                .collect(Collectors.toList());
+    }
+
+    @SafeVarargs
+    private final List<String> join(List<String>... lists) {
+        return Arrays.stream(lists).flatMap(Collection::stream).collect(Collectors.toList());
+    }
+
+    private static class FuzzyApplyTestPair {
+        public final List<String> from;
+        public final List<String> to;
+        public final int requiredFuzz;
+
+        private FuzzyApplyTestPair(List<String> from, List<String> to, int requiredFuzz) {
+            this.from = from;
+            this.to = to;
+            this.requiredFuzz = requiredFuzz;
+        }
+    }
+
+    // endregion
+
+    @Test
+    public void fuzzyApply() throws PatchFailedException {
+        Patch<String> patch = new Patch<>();
+        List<String> deltaFrom = Arrays.asList("aaa", "bbb", "ccc", "ddd", "eee", "fff");
+        List<String> deltaTo = Arrays.asList("aaa", "bbb", "cxc", "dxd", "eee", "fff");
+        patch.addDelta(new ChangeDelta<>(
+                new Chunk<>(6, deltaFrom),
+                new Chunk<>(6, deltaTo)));
+
+        //noinspection unchecked
+        List<String>[] moves = new List[] {
+                intRange(6), // no patch move
+                intRange(3), // forward patch move
+                intRange(9), // backward patch move
+                intRange(0), // apply to the first
+        };
+
+        for (FuzzyApplyTestPair pair : FUZZY_APPLY_TEST_PAIRS) {
+            for (List<String> move : moves) {
+                List<String> from = join(move, pair.from);
+                List<String> to = join(move, pair.to);
+
+                for (int i = 0; i < pair.requiredFuzz; i++) {
+                    int maxFuzz = i;
+                    assertThrows(PatchFailedException.class, () ->
+                            patch.applyFuzzy(from, maxFuzz),
+                            () -> "fail for " + from + " -> " + to + " for fuzz " + maxFuzz + " required " + pair.requiredFuzz);
+                }
+                for (int i = pair.requiredFuzz; i < 4; i++) {
+                    int maxFuzz = i;
+                    assertEquals(to, patch.applyFuzzy(from, maxFuzz),
+                            () -> "with " + maxFuzz);
+                }
+            }
+        }
+    }
+
+    @Test
+    public void fuzzyApplyTwoSideBySidePatches() throws PatchFailedException {
+        Patch<String> patch = new Patch<>();
+        List<String> deltaFrom = Arrays.asList("aaa", "bbb", "ccc", "ddd", "eee", "fff");
+        List<String> deltaTo = Arrays.asList("aaa", "bbb", "cxc", "dxd", "eee", "fff");
+        patch.addDelta(new ChangeDelta<>(
+                new Chunk<>(0, deltaFrom),
+                new Chunk<>(0, deltaTo)));
+        patch.addDelta(new ChangeDelta<>(
+                new Chunk<>(6, deltaFrom),
+                new Chunk<>(6, deltaTo)));
+
+
+        assertEquals(join(deltaTo, deltaTo), patch.applyFuzzy(join(deltaFrom, deltaFrom), 0));
+    }
+
+    @Test
+    public void fuzzyApplyToNearest() throws PatchFailedException {
+        Patch<String> patch = new Patch<>();
+        List<String> deltaFrom = Arrays.asList("aaa", "bbb", "ccc", "ddd", "eee", "fff");
+        List<String> deltaTo = Arrays.asList("aaa", "bbb", "cxc", "dxd", "eee", "fff");
+        patch.addDelta(new ChangeDelta<>(
+                new Chunk<>(0, deltaFrom),
+                new Chunk<>(0, deltaTo)));
+        patch.addDelta(new ChangeDelta<>(
+                new Chunk<>(10, deltaFrom),
+                new Chunk<>(10, deltaTo)));
+
+        assertEquals(join(deltaTo, deltaFrom, deltaTo),
+                patch.applyFuzzy(join(deltaFrom, deltaFrom, deltaFrom), 0));
+        assertEquals(join(intRange(1), deltaTo, deltaFrom, deltaTo),
+                patch.applyFuzzy(join(intRange(1), deltaFrom, deltaFrom, deltaFrom), 0));
+    }
+
     @Test
     public void testPatch_Serializable() throws IOException, ClassNotFoundException {
         final List<String> changeTest_from = Arrays.asList("aaa", "bbb", "ccc", "ddd");
@@ -101,4 +205,190 @@ public class WithMeyersDiffWithLinearSpacePatchTest {
             fail(e.getMessage());
         }
     }
+
+    static class FuzzyApplyTestDataGenerator {
+        private static String createList(List<String> values) {
+            return values.stream()
+                    .map(x -> '"' + x + '"')
+                    .collect(Collectors.joining(", ", "Arrays.asList(", ")"));
+        }
+
+        public static void main(String[] args) {
+            String[] deltaFrom = new String[] { "aaa", "bbb", "ccc", "ddd", "eee", "fff" };
+            String[] deltaTo = new String[] { "aaa", "bbb", "cxc", "dxd", "eee", "fff" };
+
+            List<FuzzyApplyTestPair> pairs = new ArrayList<>();
+
+            // create test data.
+            // Brute-force search
+            String[] changedValue = new String[]{"axa", "bxb", "czc", "dzd", "exe", "fxf"};
+            for (int i = 0; i < 1 << 6; i++) {
+                if ((i & 0b001100) != 0 && (i & 0b001100) != 0b001100) {
+                    continue;
+                }
+
+                String[] from = deltaFrom.clone();
+                String[] to = deltaTo.clone();
+                for (int j = 0; j < 6; j++) {
+                    if ((i & (1 << j)) != 0) {
+                        from[j] = changedValue[j];
+                        to[j] = changedValue[j];
+                    }
+                }
+
+                int requiredFuzz;
+                if ((i & 0b001100) != 0) {
+                    requiredFuzz = 3;
+                } else if ((i & 0b010010) != 0) {
+                    requiredFuzz = 2;
+                } else if ((i & 0b100001) != 0) {
+                    requiredFuzz = 1;
+                } else {
+                    requiredFuzz = 0;
+                }
+
+                pairs.add(new FuzzyApplyTestPair(Arrays.asList(from), Arrays.asList(to), requiredFuzz));
+            }
+            pairs.sort(Comparator.comparingInt(a -> a.requiredFuzz));
+            System.out.println("FuzzyApplyTestPair[] pairs = new FuzzyApplyTestPair[] {");
+            for (FuzzyApplyTestPair pair : pairs) {
+                System.out.println("        new FuzzyApplyTestPair(");
+                System.out.println("                " + createList(pair.from) + ",");
+                System.out.println("                " + createList(pair.to) + ",");
+                System.out.println("                " + pair.requiredFuzz + "),");
+            }
+            System.out.println("};");
+        }
+    }
+
+    private static final FuzzyApplyTestPair[] FUZZY_APPLY_TEST_PAIRS = new FuzzyApplyTestPair[] {
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bbb", "ccc", "ddd", "eee", "fff"),
+                    Arrays.asList("aaa", "bbb", "cxc", "dxd", "eee", "fff"),
+                    0),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bbb", "ccc", "ddd", "eee", "fff"),
+                    Arrays.asList("axa", "bbb", "cxc", "dxd", "eee", "fff"),
+                    1),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bbb", "ccc", "ddd", "eee", "fxf"),
+                    Arrays.asList("aaa", "bbb", "cxc", "dxd", "eee", "fxf"),
+                    1),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bbb", "ccc", "ddd", "eee", "fxf"),
+                    Arrays.asList("axa", "bbb", "cxc", "dxd", "eee", "fxf"),
+                    1),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bxb", "ccc", "ddd", "eee", "fff"),
+                    Arrays.asList("aaa", "bxb", "cxc", "dxd", "eee", "fff"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bxb", "ccc", "ddd", "eee", "fff"),
+                    Arrays.asList("axa", "bxb", "cxc", "dxd", "eee", "fff"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bbb", "ccc", "ddd", "exe", "fff"),
+                    Arrays.asList("aaa", "bbb", "cxc", "dxd", "exe", "fff"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bbb", "ccc", "ddd", "exe", "fff"),
+                    Arrays.asList("axa", "bbb", "cxc", "dxd", "exe", "fff"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bxb", "ccc", "ddd", "exe", "fff"),
+                    Arrays.asList("aaa", "bxb", "cxc", "dxd", "exe", "fff"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bxb", "ccc", "ddd", "exe", "fff"),
+                    Arrays.asList("axa", "bxb", "cxc", "dxd", "exe", "fff"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bxb", "ccc", "ddd", "eee", "fxf"),
+                    Arrays.asList("aaa", "bxb", "cxc", "dxd", "eee", "fxf"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bxb", "ccc", "ddd", "eee", "fxf"),
+                    Arrays.asList("axa", "bxb", "cxc", "dxd", "eee", "fxf"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bbb", "ccc", "ddd", "exe", "fxf"),
+                    Arrays.asList("aaa", "bbb", "cxc", "dxd", "exe", "fxf"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bbb", "ccc", "ddd", "exe", "fxf"),
+                    Arrays.asList("axa", "bbb", "cxc", "dxd", "exe", "fxf"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bxb", "ccc", "ddd", "exe", "fxf"),
+                    Arrays.asList("aaa", "bxb", "cxc", "dxd", "exe", "fxf"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bxb", "ccc", "ddd", "exe", "fxf"),
+                    Arrays.asList("axa", "bxb", "cxc", "dxd", "exe", "fxf"),
+                    2),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bbb", "czc", "dzd", "eee", "fff"),
+                    Arrays.asList("aaa", "bbb", "czc", "dzd", "eee", "fff"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bbb", "czc", "dzd", "eee", "fff"),
+                    Arrays.asList("axa", "bbb", "czc", "dzd", "eee", "fff"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bxb", "czc", "dzd", "eee", "fff"),
+                    Arrays.asList("aaa", "bxb", "czc", "dzd", "eee", "fff"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bxb", "czc", "dzd", "eee", "fff"),
+                    Arrays.asList("axa", "bxb", "czc", "dzd", "eee", "fff"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bbb", "czc", "dzd", "exe", "fff"),
+                    Arrays.asList("aaa", "bbb", "czc", "dzd", "exe", "fff"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bbb", "czc", "dzd", "exe", "fff"),
+                    Arrays.asList("axa", "bbb", "czc", "dzd", "exe", "fff"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bxb", "czc", "dzd", "exe", "fff"),
+                    Arrays.asList("aaa", "bxb", "czc", "dzd", "exe", "fff"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bxb", "czc", "dzd", "exe", "fff"),
+                    Arrays.asList("axa", "bxb", "czc", "dzd", "exe", "fff"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bbb", "czc", "dzd", "eee", "fxf"),
+                    Arrays.asList("aaa", "bbb", "czc", "dzd", "eee", "fxf"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bbb", "czc", "dzd", "eee", "fxf"),
+                    Arrays.asList("axa", "bbb", "czc", "dzd", "eee", "fxf"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bxb", "czc", "dzd", "eee", "fxf"),
+                    Arrays.asList("aaa", "bxb", "czc", "dzd", "eee", "fxf"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bxb", "czc", "dzd", "eee", "fxf"),
+                    Arrays.asList("axa", "bxb", "czc", "dzd", "eee", "fxf"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bbb", "czc", "dzd", "exe", "fxf"),
+                    Arrays.asList("aaa", "bbb", "czc", "dzd", "exe", "fxf"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bbb", "czc", "dzd", "exe", "fxf"),
+                    Arrays.asList("axa", "bbb", "czc", "dzd", "exe", "fxf"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("aaa", "bxb", "czc", "dzd", "exe", "fxf"),
+                    Arrays.asList("aaa", "bxb", "czc", "dzd", "exe", "fxf"),
+                    3),
+            new FuzzyApplyTestPair(
+                    Arrays.asList("axa", "bxb", "czc", "dzd", "exe", "fxf"),
+                    Arrays.asList("axa", "bxb", "czc", "dzd", "exe", "fxf"),
+                    3),
+    };
 }

java-diff-utils/src/test/java/com/github/difflib/patch/ChunkTest.java

@@ -0,0 +1,43 @@
+package com.github.difflib.patch;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ChunkTest {
+    @Test
+    void verifyChunk() throws PatchFailedException {
+        Chunk<Character> chunk = new Chunk<>(7, toCharList("test"));
+
+        // normal check
+        assertEquals(VerifyChunk.OK,
+                chunk.verifyChunk(toCharList("prefix test suffix")));
+        assertEquals(VerifyChunk.CONTENT_DOES_NOT_MATCH_TARGET,
+                chunk.verifyChunk(toCharList("prefix  es  suffix"), 0, 7));
+
+        // position
+        assertEquals(VerifyChunk.OK,
+                chunk.verifyChunk(toCharList("short test suffix"), 0, 6));
+        assertEquals(VerifyChunk.OK,
+                chunk.verifyChunk(toCharList("loonger test suffix"), 0, 8));
+        assertEquals(VerifyChunk.CONTENT_DOES_NOT_MATCH_TARGET,
+                chunk.verifyChunk(toCharList("prefix test suffix"), 0, 6));
+        assertEquals(VerifyChunk.CONTENT_DOES_NOT_MATCH_TARGET,
+                chunk.verifyChunk(toCharList("prefix test suffix"), 0, 8));
+
+        // fuzz
+        assertEquals(VerifyChunk.OK,
+                chunk.verifyChunk(toCharList("prefix test suffix"), 1, 7));
+        assertEquals(VerifyChunk.OK,
+                chunk.verifyChunk(toCharList("prefix  es  suffix"), 1, 7));
+        assertEquals(VerifyChunk.CONTENT_DOES_NOT_MATCH_TARGET,
+                chunk.verifyChunk(toCharList("prefix      suffix"), 1, 7));
+    }
+
+    private List<Character> toCharList(String str) {
+        return str.chars().mapToObj(x -> (char) x).collect(Collectors.toList());
+    }
+}