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/* Copyright (C) 2013-2019 TU Dortmund
* This file is part of AutomataLib, http://www.automatalib.net/.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package net.automatalib.util.automata.conformance;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import net.automatalib.automata.UniversalDeterministicAutomaton;
import net.automatalib.commons.util.collections.AbstractThreeLevelIterator;
import net.automatalib.commons.util.collections.CollectionsUtil;
import net.automatalib.commons.util.collections.ReusableIterator;
import net.automatalib.util.automata.cover.Covers;
import net.automatalib.util.automata.equivalence.CharacterizingSets;
import net.automatalib.words.Word;
import net.automatalib.words.WordBuilder;
/**
* Iterator that returns test words generated by the W Method.
*
* See "Testing software design modeled by finite-state machines" by Tsun S. Chow.
*
* @param
* input symbol type
*
* @author Malte Isberner
*/
public class WMethodTestsIterator extends AbstractThreeLevelIterator, Word, Word, Word> {
private final Iterable> prefixes;
private final Iterable> suffixes;
private final WordBuilder wordBuilder = new WordBuilder<>();
public WMethodTestsIterator(UniversalDeterministicAutomaton automaton,
Collection inputs,
int maxDepth) {
super(CollectionsUtil.allTuples(inputs, 0, maxDepth).iterator());
this.prefixes = new ReusableIterator<>(Covers.transitionCoverIterator(automaton, inputs),
new ArrayList<>(automaton.size() * inputs.size()));
final Iterator> characterizingSet = CharacterizingSets.characterizingSetIterator(automaton, inputs);
// Special case: List of characterizing suffixes may be empty,
// but in this case we still need to iterate over the prefixes!
if (!characterizingSet.hasNext()) {
this.suffixes = Collections.singletonList(Word.epsilon());
} else {
this.suffixes = new ReusableIterator<>(characterizingSet);
}
}
@Override
protected Iterator> l2Iterator(List l1Object) {
return prefixes.iterator();
}
@Override
protected Iterator> l3Iterator(List l1Object, Word l2Object) {
return suffixes.iterator();
}
@Override
protected Word combine(List middle, Word prefix, Word suffix) {
wordBuilder.ensureAdditionalCapacity(prefix.size() + middle.size() + suffix.size());
Word word = wordBuilder.append(prefix).append(middle).append(suffix).toWord();
wordBuilder.clear();
return word;
}
}