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Add PlusMinusOptmizer to analyse sequences of +-><, addressing #28 
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‎src/main/groovy/net/zomis/brainf/analyze/analyzers/BrainfuckAnalyzers.groovy‎

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@@ -13,6 +13,7 @@ class BrainfuckAnalyzers {
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new WhileLoopAnalysis(),
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new CommandCountAnalysis(),
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new MemoryIndexAnalysis(),
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new PlusMinusOptimizer(),
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]
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analyzers
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}

‎src/main/groovy/net/zomis/brainf/analyze/analyzers/PlusMinusOptimizer.groovy‎

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package net.zomis.brainf.analyze.analyzers
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import net.zomis.brainf.analyze.Brainalyze
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import net.zomis.brainf.analyze.BrainfuckAnalyzer
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import net.zomis.brainf.analyze.InspectionResult
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import net.zomis.brainf.analyze.MemoryCell
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import net.zomis.brainf.model.BrainfuckCommand
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import net.zomis.brainf.model.BrainfuckRunner
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import net.zomis.brainf.model.classic.BrainFCommand
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class PlusMinusOptimizer implements BrainfuckAnalyzer {
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private static final Set<BrainfuckCommand> handlableCommands = [BrainFCommand.ADD, BrainFCommand.SUBTRACT,
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BrainFCommand.NEXT, BrainFCommand.PREVIOUS] as Set
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private final List<InspectionResult> results = []
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private List<Integer> changesLeft = new ArrayList<>()
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private List<Integer> changesRight = new ArrayList<>()
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private int pointerChange
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private int commandStart
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private int commandsUsed
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@Override
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void after(Brainalyze analyze, BrainfuckRunner runner) {
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finishAndReset(runner)
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results.each {
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analyze.addInspectionResult(it)
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}
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}
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@Override
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void beforePerform(MemoryCell cell, BrainfuckRunner runner, BrainfuckCommand command) {
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if (!(command instanceof BrainFCommand)) {
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return
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}
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if (command == BrainFCommand.NONE) {
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return
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}
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if (!handlableCommands.contains(command)) {
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finishAndReset(runner)
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return
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}
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BrainFCommand cmd = (BrainFCommand) command
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switch (cmd) {
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case BrainFCommand.PREVIOUS:
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pointerMove(-1)
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break
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case BrainFCommand.NEXT:
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pointerMove(1)
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break
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case BrainFCommand.SUBTRACT:
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valueChange(-1)
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break
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case BrainFCommand.ADD:
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valueChange(1)
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break
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default:
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throw new IllegalStateException('Unexpected command: ' + command)
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}
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commandsUsed++
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}
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void valueChange(int i) {
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int index = pointerChange
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List list
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if (pointerChange >= 0) {
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list = changesRight
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} else {
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index = Math.abs(pointerChange) - 1
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list = changesLeft
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}
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while (list.size() <= index) {
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list.add(0)
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}
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list.set(index, list.get(index) + i)
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}
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void pointerMove(int i) {
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pointerChange += i
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}
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boolean finishAndReset(BrainfuckRunner runner) {
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trim(changesLeft)
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trim(changesRight)
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// find out if it's better to go to the `pointerChange` from left or right
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// >>>>> + <<<<< <<<<< <<<<< - > + for example is better to go right first, then left
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int leftCost = changesLeft.size() + pointerChange
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int rightCost = changesRight.size() - 1 - pointerChange
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boolean fromLeftToEnd = leftCost < rightCost
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StringBuilder str = new StringBuilder()
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if (fromLeftToEnd) {
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if (!changesRight.isEmpty()) {
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str.append(code(changesRight, '>' as char))
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str.append('<' * (changesRight.size() - 1))
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}
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if (!changesLeft.isEmpty()) {
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str.append('<')
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str.append(code(changesLeft, '<' as char))
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}
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if (leftCost > 0) {
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str.append('>' * leftCost)
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} else {
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str.append('<' * -leftCost)
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}
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} else {
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if (!changesLeft.isEmpty()) {
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str.append('<')
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str.append(code(changesLeft, '<' as char))
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str.append('>' * changesLeft.size())
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}
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if (!changesRight.isEmpty()) {
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str.append(code(changesRight, '>' as char))
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}
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if (rightCost > 0) {
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str.append('<' * rightCost)
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} else {
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str.append('>' * -rightCost)
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}
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}
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String shortestCode = str.toString()
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if (shortestCode.length() < this.commandsUsed) {
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this.results.add(new InspectionResult(InspectionResult.InspectionSeverity.HINT,
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commandStart, runner.code.commandIndex,
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"Code is unnecessarily complicated. Can be written as '$shortestCode'"))
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}
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changesLeft.clear()
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changesRight.clear()
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pointerChange = 0
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commandStart = 0
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commandsUsed = 0
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}
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static String code(List<Integer> list, char ch) {
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StringBuilder str = new StringBuilder()
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def it = list.listIterator()
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while (it.hasNext()) {
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int value = it.next()
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if (value > 0) {
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str.append('+' * value)
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}
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if (value < 0) {
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value = Math.abs(value)
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str.append('-' * value)
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}
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if (it.hasNext()) {
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str.append(ch)
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}
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}
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str.toString()
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}
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static void trim(List<Integer> integers) {
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while (!integers.isEmpty() && integers.get(integers.size() - 1) == 0) {
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integers.remove(integers.size() - 1)
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}
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}
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}

‎src/test/groovy/net/zomis/brainf/OptimizeTest.java‎

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package net.zomis.brainf;
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import net.zomis.brainf.analyze.InspectionResult;
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import net.zomis.brainf.analyze.analyzers.PlusMinusOptimizer;
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import org.junit.Assert;
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import org.junit.Test;
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import org.junit.runner.RunWith;
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import org.junit.runners.Parameterized;
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import java.util.Arrays;
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import java.util.Collection;
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import java.util.List;
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@RunWith(Parameterized.class)
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public class OptimizeTest extends BrainfuckTest {
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@Parameterized.Parameters
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public static Collection<Object[]> data() {
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return Arrays.asList(new Object[][]{
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{"+>+++<++>--<->+>", "++>++>"},
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{">>>+++<<< <+> >>--", "<+>>>-->+++<"}, // -1, +3, end at +2. from right to pos
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{"<<<<< + >>>>> >+< <", null}, // -5, +1, end at -1. from right to pos
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{"+>+", null},
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{"+-", ""},
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{"<>", ""},
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{"+-<>", ""},
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{"+>-<->+<", ""},
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{"+>-<+>-<", "++>--<"},
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{"<+>-<+>-", "<++>--"},
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});
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}
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@Parameterized.Parameter(0)
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public String original;
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@Parameterized.Parameter(1)
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public String cleaned;
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@Test
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public void test() {
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getSource().addCommands(original);
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analyze(new PlusMinusOptimizer());
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System.out.println(getAnalyze().getInspectionResults());
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List<InspectionResult> results = getAnalyze().getInspectionResults();
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String actual = results.isEmpty() ? null : results.get(0).getDescription();
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String str = String.format("%s resulted in %s and not the expected %s", original, actual, cleaned);
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if (cleaned == null) {
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Assert.assertTrue(str, getAnalyze().getInspectionResults().isEmpty());
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return;
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}
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Assert.assertFalse(str, getAnalyze().getInspectionResults().isEmpty());
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Assert.assertTrue(str, getAnalyze().getInspectionResults().get(0).getDescription()
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.contains(cleaned));
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}
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}

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