Fixing #320: Correcting the delta computation

src/main/java/org/codehaus/mojo/versions/rewriting/ModifiedPomXMLEventReader.java

@@ -462,7 +462,7 @@ public void replace( String replacement )
             return;
         }
         pom.replace( start, end, replacement );
-        int delta = replacement.length() - lastEnd - lastStart;
+        int delta = replacement.length() - ( lastEnd - lastStart );
         nextDelta += delta;
         for ( int i = 0; i < MAX_MARKS; i++ )
         {
@@ -563,7 +563,7 @@ public void replaceMark( int index, String replacement )
             return;
         }
         pom.replace( start, end, replacement );
-        int delta = replacement.length() - markEnd[index] - markStart[index];
+        int delta = replacement.length() - ( markEnd[index] - markStart[index] );
         nextDelta += delta;
         if ( lastStart == markStart[index] && lastEnd == markEnd[index] )
         {

src/test/java/org/codehaus/mojo/versions/rewriting/ModifiedPomXMLEventReaderTest.java

@@ -0,0 +1,138 @@
+package org.codehaus.mojo.versions.rewriting;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+
+import javax.xml.stream.Location;
+import javax.xml.stream.XMLEventReader;
+import javax.xml.stream.XMLInputFactory;
+import javax.xml.stream.XMLStreamException;
+import javax.xml.stream.events.XMLEvent;
+
+import java.io.StringReader;
+
+import org.apache.maven.plugin.testing.AbstractMojoTestCase;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.core.Is.is;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.when;
+
+/**
+ * Unit tests for {@link ModifiedPomXMLEventReaderTest}
+ *
+ * @author Andrzej Jarmoniuk
+ */
+
+@RunWith( MockitoJUnitRunner.class )
+public class ModifiedPomXMLEventReaderTest extends AbstractMojoTestCase
+{
+    private static final String[] STR = {"xyz", "0123456789abcdef"};
+    private static final String REPLACEMENT = "abcdef";
+
+    @Mock
+    private Location location;
+
+    @Mock
+    private XMLEvent xmlEvent;
+
+    @Mock
+    private XMLEventReader xmlEventReader;
+
+    @Mock
+    private XMLInputFactory xmlInputFactory;
+
+    private ModifiedPomXMLEventReader pomXMLEventReader;
+
+    @Before
+    public void setUp() throws Exception
+    {
+        super.setUp();
+
+        when( location.getCharacterOffset() )
+                .thenReturn( STR[0].length() )
+                .thenReturn( STR[0].length() + STR[1].length() );
+
+        when( xmlEvent.isCharacters() ).thenReturn( true );
+        when( xmlEvent.getLocation() ).thenReturn( location );
+
+        when( xmlEventReader.hasNext() )
+                .thenReturn( true ).thenReturn( true )  // str[0]
+                .thenReturn( true ).thenReturn( true )  // str[1]
+                .thenReturn( false );                      // ∅
+        when( xmlEventReader.nextEvent() )
+                .thenReturn( xmlEvent )
+                .thenReturn( xmlEvent );
+        when( xmlEventReader.peek() )
+                .thenReturn( xmlEvent );
+
+        when( xmlInputFactory.createXMLEventReader( any( StringReader.class ) ) )
+                .thenReturn( xmlEventReader );
+
+        pomXMLEventReader =
+                new ModifiedPomXMLEventReader( new StringBuilder( STR[0] ).append( STR[1] ), xmlInputFactory, "" );
+    }
+
+    @Test
+    public void testReplace() throws XMLStreamException, IllegalAccessException
+    {
+        assertThat( pomXMLEventReader.hasNext(), is( true ) );
+        assertThat( pomXMLEventReader.nextEvent(), is( xmlEvent ) );
+
+        assertThat( pomXMLEventReader.hasNext(), is( true ) );
+        assertThat( pomXMLEventReader.nextEvent(), is( xmlEvent ) );
+
+        pomXMLEventReader.replace( REPLACEMENT );
+        assertThat( pomXMLEventReader.asStringBuilder().toString(), is( STR[0] + REPLACEMENT ) );
+
+        pomXMLEventReader.mark( 0 );
+        assertThat( pomXMLEventReader.getMarkVerbatim( 0 ), is( REPLACEMENT ) );
+
+        // more dangerous test since this touches the implementation
+        assertThat( getVariableValueFromObject( pomXMLEventReader, "lastEnd" ),
+                is( ( STR[0] + REPLACEMENT ).length() ) );
+    }
+
+    @Test
+    public void testReplaceMark() throws XMLStreamException, IllegalAccessException
+    {
+        assertThat( pomXMLEventReader.hasNext(), is( true ) );
+        assertThat( pomXMLEventReader.nextEvent(), is( xmlEvent ) );
+
+        assertThat( pomXMLEventReader.hasNext(), is( true ) );
+        assertThat( pomXMLEventReader.nextEvent(), is( xmlEvent ) );
+
+        pomXMLEventReader.mark( 0 );
+
+        pomXMLEventReader.replaceMark( 0, REPLACEMENT );
+        assertThat( pomXMLEventReader.asStringBuilder().toString(), is( STR[0] + REPLACEMENT ) );
+
+        pomXMLEventReader.mark( 0 );
+        assertThat( pomXMLEventReader.getMarkVerbatim( 0 ), is( REPLACEMENT ) );
+
+        // more dangerous test since this touches the implementation
+        assertThat( getVariableValueFromObject( pomXMLEventReader, "lastEnd" ),
+                is( ( STR[0] + REPLACEMENT ).length() ) );
+    }
+}