Added test to highlight caveats of the ignoreCase() method

src/test/java/org/ahocorasick/trie/PrioritizeLeftLongestMatchTest.java

@@ -0,0 +1,83 @@
+package org.ahocorasick.trie;
+
+import org.junit.Test;
+
+import java.util.Collection;
+import java.util.Iterator;
+
+import static org.junit.Assert.assertEquals;
+
+public class PrioritizeLeftLongestMatchTest {
+
+    /**
+     * This test shows correct matching of the longest, left-most matches
+     */
+    @Test
+    public void testPrioritizeLeftLongestMatchExpectedBehaviour() {
+        final Trie trie = Trie.builder()
+                .ignoreCase()
+                .ignoreOverlaps()
+                .onlyWholeWords()
+                .addKeyword("RESPIRATORY TRACT INFECTIONS")  // correct: match
+                .addKeyword("URINARY TRACT INFECTIONS")  // correct: match
+                .addKeyword("URINARY")  // correct: no match
+                .addKeyword("INTRA-ABDOMINAL INFECTIONS")  // correct: match
+                .build();
+
+        final Collection<Emit> emits = trie.parseText(
+                "lower respiratory tract infections, urinary tract infections, intra-abdominal infections, and more.");
+
+        assertEquals(3, emits.size()); // she @ 3, he @ 3, hers @ 5
+        final Iterator<Emit> iterator = emits.iterator();
+
+        // expected as longest match on start index 6
+        checkEmit(iterator.next(), 6, 33, "RESPIRATORY TRACT INFECTIONS");
+
+        // expected as longest match on start index 36
+        checkEmit(iterator.next(), 36, 59, "URINARY TRACT INFECTIONS");
+
+        // expected, as longest match on start index 62
+        checkEmit(iterator.next(), 62, 87, "INTRA-ABDOMINAL INFECTIONS");
+
+    }
+
+    /**
+     * This test shows that when exchanging the keyword "intra-abdominal infections" for "infections, intra-abdominal",
+     * the 2nd match from left to right in the text is wrong, as "urinary" is matched over "urinary tract infections"
+     */
+    @Test
+    public void testPrioritizeLeftLongestMatchUnexpectedBehaviour() {
+        final Trie trie = Trie.builder()
+                .ignoreCase()
+                .ignoreOverlaps()
+                .onlyWholeWords()
+                .addKeyword("RESPIRATORY TRACT INFECTIONS")  // correct: match
+                .addKeyword("URINARY TRACT INFECTIONS")  // incorrect: no match
+                .addKeyword("URINARY")  // incorrect: match
+                .addKeyword("INFECTIONS, INTRA-ABDOMINAL")  // incorrect: match
+                .build();
+
+        final Collection<Emit> emits = trie.parseText(
+                "lower respiratory tract infections, urinary tract infections, intra-abdominal infections, and more.");
+
+        assertEquals(3, emits.size()); // she @ 3, he @ 3, hers @ 5
+        final Iterator<Emit> iterator = emits.iterator();
+
+        // expected as longest match on start index 6
+        checkEmit(iterator.next(), 6, 33, "RESPIRATORY TRACT INFECTIONS");
+
+        // unexpected, as "urinary tract infections" shares same start index 6 and "urinary" is a shorter match
+        checkEmit(iterator.next(), 36, 42, "URINARY");
+
+        // unexpected, as "urinary tract infections" should be the left-longest match from previous iteration and
+        // "infections" starting at index 50 should not be considered anymore
+        checkEmit(iterator.next(), 50, 76, "INFECTIONS, INTRA-ABDOMINAL");
+    }
+
+  private void checkEmit( Emit next, int expectedStart, int expectedEnd,
+                          String expectedKeyword ) {
+    assertEquals("Start of emit should have been " + expectedStart, expectedStart, next.getStart());
+    assertEquals("End of emit should have been " + expectedEnd, expectedEnd, next.getEnd());
+    assertEquals(expectedKeyword, next.getKeyword());
+  }
+}