ReducedNode.java

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/*******************************************************************************
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 * Copyright (C) 2026, Leo Galambos
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions are met:
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 *
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 * 1. Redistributions of source code must retain the above copyright notice,
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 *    this list of conditions and the following disclaimer.
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 *
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 * 2. Redistributions in binary form must reproduce the above copyright notice,
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 *    this list of conditions and the following disclaimer in the documentation
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 *    and/or other materials provided with the distribution.
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 *
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 * 3. Neither the name of the copyright holder nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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 * POSSIBILITY OF SUCH DAMAGE.
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 ******************************************************************************/
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package org.egothor.stemmer.trie;
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import java.util.LinkedHashMap;
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import java.util.Map;
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/**
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 * Canonical reduced node used during subtree merging.
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 *
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 * <p>
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 * The maps exposed by the accessors are the internal backing state of the
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 * canonical reduced node. They are returned directly for efficiency and are
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 * intended only for closely related trie-reduction infrastructure.
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 * </p>
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 *
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 * <p>
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 * Instances are mutable only during one builder compilation and are confined to
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 * its reduction context. They are converted to immutable {@link CompiledNode}
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 * instances before becoming observable to lookup callers.
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 * </p>
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 *
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 * @param <V> value type
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 */
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public final class ReducedNode<V> {
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    /**
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     * Reduction signature.
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     */
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    private final ReductionSignature<V> signature;
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    /**
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     * Aggregated local value counts.
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     */
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    private final Map<V, Integer> localCounts;
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    /**
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     * Canonical children by edge.
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     */
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    private final Map<Character, ReducedNode<V>> children;
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    /**
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     * Whether this reduced node accepts any remaining lookup input.
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     */
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    private final boolean acceptsRemainingInput;
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    /**
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     * Creates a new reduced node.
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     *
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     * @param signature   reduction signature
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     * @param localCounts local counts
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     * @param children    children
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     * @param acceptsRemainingInput whether this node accepts any remaining lookup
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     *                              input
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     */
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    public ReducedNode(final ReductionSignature<V> signature, final Map<V, Integer> localCounts,
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            final Map<Character, ReducedNode<V>> children, final boolean acceptsRemainingInput) {
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        this.signature = signature;
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        this.localCounts = new LinkedHashMap<>(localCounts);
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        this.children = new LinkedHashMap<>(children);
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        this.acceptsRemainingInput = acceptsRemainingInput;
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    }
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    /**
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     * Creates a new non-accepting reduced node.
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     *
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     * @param signature   reduction signature
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     * @param localCounts local counts
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     * @param children    children
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     */
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    public ReducedNode(final ReductionSignature<V> signature, final Map<V, Integer> localCounts,
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            final Map<Character, ReducedNode<V>> children) {
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        this(signature, localCounts, children, false);
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    }
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    /**
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     * Returns the reduction signature of this canonical node.
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     *
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     * @return reduction signature
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     */
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    public ReductionSignature<V> signature() {
110 1 1. signature : replaced return value with null for org/egothor/stemmer/trie/ReducedNode::signature → KILLED
 
        return this.signature;
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    }
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    /**
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     * Returns the internal aggregated local value-count map.
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     *
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     * <p>
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     * The returned map is the internal backing state of this canonical reduced node
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     * and is exposed only for efficient cooperation with trie-reduction
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     * infrastructure.
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     *
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     * @return internal aggregated local value-count map
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     */
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    public Map<V, Integer> localCounts() {
124 1 1. localCounts : replaced return value with Collections.emptyMap for org/egothor/stemmer/trie/ReducedNode::localCounts → KILLED
 
        return this.localCounts;
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    }
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    /**
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     * Returns the internal canonical child map indexed by transition character.
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     *
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     * <p>
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     * The returned map is the internal backing state of this canonical reduced node
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     * and is exposed only for efficient cooperation with trie-reduction
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     * infrastructure.
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     *
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     * @return internal canonical child map
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     */
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    public Map<Character, ReducedNode<V>> children() {
138 1 1. children : replaced return value with Collections.emptyMap for org/egothor/stemmer/trie/ReducedNode::children → KILLED
 
        return this.children;
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    }
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    /**
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     * Returns whether this node accepts any remaining lookup input.
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     *
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     * @return {@code true} for a contracted accepting leaf
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     */
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    public boolean acceptsRemainingInput() {
147 2 1. acceptsRemainingInput : replaced boolean return with false for org/egothor/stemmer/trie/ReducedNode::acceptsRemainingInput → KILLED
2. acceptsRemainingInput : replaced boolean return with true for org/egothor/stemmer/trie/ReducedNode::acceptsRemainingInput → KILLED
 
        return this.acceptsRemainingInput;
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    }
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    /**
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     * Merges additional local counts into this node.
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     *
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     * @param additionalCounts additional local counts
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     * @throws ArithmeticException if an aggregated count exceeds
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     *                             {@link Integer#MAX_VALUE}
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     */
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    public void mergeLocalCounts(final Map<V, Integer> additionalCounts) {
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        for (Map.Entry<V, Integer> entry : additionalCounts.entrySet()) {
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            final Integer previous = this.localCounts.get(entry.getKey());
160 1 1. mergeLocalCounts : negated conditional → KILLED
 
            if (previous == null) {
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                this.localCounts.put(entry.getKey(), entry.getValue());
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            } else {
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                this.localCounts.put(entry.getKey(), Math.addExact(previous, entry.getValue()));
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            }
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        }
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    }
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    /**
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     * Merges child references into this node.
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     *
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     * <p>
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     * For nodes with the same reduction signature, child edge sets and child
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     * signatures must be compatible. This method therefore only needs to verify
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     * consistency and store the canonical child instance.
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     *
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     * @param additionalChildren additional children
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     */
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    public void mergeChildren(final Map<Character, ReducedNode<V>> additionalChildren) {
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        for (Map.Entry<Character, ReducedNode<V>> entry : additionalChildren.entrySet()) {
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            final ReducedNode<V> existing = this.children.get(entry.getKey());
181 1 1. mergeChildren : negated conditional → KILLED
 
            if (existing == null) {
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                this.children.put(entry.getKey(), entry.getValue());
183 1 1. mergeChildren : negated conditional → KILLED
 
            } else if (existing != entry.getValue()) { // NOPMD - we have canonical instances
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                throw new IllegalStateException("Incompatible canonical child encountered during reduction.");
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            }
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        }
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    }
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}

Mutations

110

1.1
Location : signature
Killed by : org.egothor.stemmer.trie.ReductionSignatureTest.[engine:junit-jupiter]/[class:org.egothor.stemmer.trie.ReductionSignatureTest]/[method:shouldIncludeChildSignaturesInEquality()] replaced return value with null for org/egothor/stemmer/trie/ReducedNode::signature → KILLED

124

1.1
Location : localCounts
Killed by : org.egothor.stemmer.trie.ReducedNodeTest.[engine:junit-jupiter]/[class:org.egothor.stemmer.trie.ReducedNodeTest]/[method:shouldExposeInternalBackingLocalCountsMap()] replaced return value with Collections.emptyMap for org/egothor/stemmer/trie/ReducedNode::localCounts → KILLED

138

1.1
Location : children
Killed by : org.egothor.stemmer.trie.ReducedNodeTest.[engine:junit-jupiter]/[class:org.egothor.stemmer.trie.ReducedNodeTest]/[method:shouldExposeInternalBackingChildrenMap()] replaced return value with Collections.emptyMap for org/egothor/stemmer/trie/ReducedNode::children → KILLED

147

1.1
Location : acceptsRemainingInput
Killed by : org.egothor.stemmer.FrequencyTrieTest.[engine:junit-jupiter]/[class:org.egothor.stemmer.FrequencyTrieTest]/[method:shouldPreserveUniformSubtreeContractionWhenMappingValues()] replaced boolean return with false for org/egothor/stemmer/trie/ReducedNode::acceptsRemainingInput → KILLED

2.2
Location : acceptsRemainingInput
Killed by : org.egothor.stemmer.FrequencyTrieTest.[engine:junit-jupiter]/[class:org.egothor.stemmer.FrequencyTrieTest]/[method:trieRejectsNullLookupKeys()] replaced boolean return with true for org/egothor/stemmer/trie/ReducedNode::acceptsRemainingInput → KILLED

160

1.1
Location : mergeLocalCounts
Killed by : org.egothor.stemmer.trie.ReducedNodeTest.[engine:junit-jupiter]/[class:org.egothor.stemmer.trie.ReducedNodeTest]/[method:shouldMergeLocalCountsBySummingAndAppending()] negated conditional → KILLED

181

1.1
Location : mergeChildren
Killed by : org.egothor.stemmer.trie.ReducedNodeTest.[engine:junit-jupiter]/[class:org.egothor.stemmer.trie.ReducedNodeTest]/[method:shouldAppendChildWhenEdgeIsAbsent()] negated conditional → KILLED

183

1.1
Location : mergeChildren
Killed by : org.egothor.stemmer.trie.ReducedNodeTest.[engine:junit-jupiter]/[class:org.egothor.stemmer.trie.ReducedNodeTest]/[method:shouldAllowSameCanonicalChildInstanceForSameEdge()] negated conditional → KILLED

Active mutators

Tests examined


Report generated by PIT 1.22.1