diff --git a/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFRichTextString.java b/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFRichTextString.java
index c58795075..13a1de914 100644
--- a/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFRichTextString.java
+++ b/src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFRichTextString.java
@@ -135,9 +135,10 @@ public class XSSFRichTextString implements RichTextString {
      */
     public void applyFont(int startIndex, int endIndex, Font font) {
         if (startIndex > endIndex)
-            throw new IllegalArgumentException("Start index must be less than end index.");
+            throw new IllegalArgumentException("Start index must be less than end index, but had " + startIndex + " and " + endIndex);
         if (startIndex < 0 || endIndex > length())
-            throw new IllegalArgumentException("Start and end index not in range.");
+            throw new IllegalArgumentException("Start and end index not in range, but had " + startIndex + " and " + endIndex);
+
         if (startIndex == endIndex)
             return;
 
diff --git a/src/ooxml/testcases/org/apache/poi/xssf/usermodel/TestXSSFRichTextString.java b/src/ooxml/testcases/org/apache/poi/xssf/usermodel/TestXSSFRichTextString.java
index 3daa570b9..8edf1930e 100644
--- a/src/ooxml/testcases/org/apache/poi/xssf/usermodel/TestXSSFRichTextString.java
+++ b/src/ooxml/testcases/org/apache/poi/xssf/usermodel/TestXSSFRichTextString.java
@@ -25,6 +25,7 @@ import junit.framework.TestCase;
 import org.apache.poi.ss.usermodel.Row;
 import org.apache.poi.ss.usermodel.Sheet;
 import org.apache.poi.xssf.XSSFTestDataSamples;
+import org.apache.poi.xssf.model.StylesTable;
 import org.junit.Test;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTRPrElt;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTRst;
@@ -38,7 +39,6 @@ import org.openxmlformats.schemas.spreadsheetml.x2006.main.STXstring;
 public final class TestXSSFRichTextString extends TestCase {
 
     public void testCreate() {
-
         XSSFRichTextString rt = new XSSFRichTextString("Apache POI");
         assertEquals("Apache POI", rt.getString());
 
@@ -53,9 +53,14 @@ public final class TestXSSFRichTextString extends TestCase {
         assertEquals("Apache POI is cool stuff", rt.getString());
     }
 
+    public void testEmpty() {
+        XSSFRichTextString rt = new XSSFRichTextString();
+        assertEquals(0, rt.getIndexOfFormattingRun(9999));
+        assertEquals(-1, rt.getLengthOfFormattingRun(9999));
+        assertNull(rt.getFontAtIndex(9999));
+    }
 
     public void testApplyFont() {
-
         XSSFRichTextString rt = new XSSFRichTextString();
         rt.append("123");
         rt.append("4567");
@@ -82,6 +87,65 @@ public final class TestXSSFRichTextString extends TestCase {
         assertEquals(7, rt.getIndexOfFormattingRun(3));
         assertEquals(2, rt.getLengthOfFormattingRun(3));
         assertEquals("89", rt.getCTRst().getRArray(3).getT());
+        
+        
+        assertEquals(-1, rt.getIndexOfFormattingRun(9999));
+        assertEquals(-1, rt.getLengthOfFormattingRun(9999));
+        assertNull(rt.getFontAtIndex(9999));
+    }
+
+    public void testApplyFontIndex() {
+        XSSFRichTextString rt = new XSSFRichTextString("Apache POI");
+        rt.applyFont(0, 10, (short)1);
+        
+        rt.applyFont((short)1);
+        
+        assertNotNull(rt.getFontAtIndex(0));
+    }
+
+    public void testApplyFontWithStyles() {
+        XSSFRichTextString rt = new XSSFRichTextString("Apache POI");
+        
+        StylesTable tbl = new StylesTable();
+        rt.setStylesTableReference(tbl);
+        
+        try {
+            rt.applyFont(0, 10, (short)1);
+            fail("Fails without styles in the table");
+        } catch (IndexOutOfBoundsException e) {
+            // expected
+        }
+        
+        tbl.putFont(new XSSFFont());
+        rt.applyFont(0, 10, (short)1);
+        rt.applyFont((short)1);
+    }
+
+    public void testApplyFontException() {
+        XSSFRichTextString rt = new XSSFRichTextString("Apache POI");
+        
+        rt.applyFont(0, 0, (short)1);
+
+        try {
+            rt.applyFont(11, 10, (short)1);
+            fail("Should catch Exception here");
+        } catch (IllegalArgumentException e) {
+            assertTrue(e.getMessage().contains("11"));
+        }
+
+        try {
+            rt.applyFont(-1, 10, (short)1);
+            fail("Should catch Exception here");
+        } catch (IllegalArgumentException e) {
+            assertTrue(e.getMessage().contains("-1"));
+        }
+
+        try {
+            rt.applyFont(0, 555, (short)1);
+            fail("Should catch Exception here");
+        } catch (IllegalArgumentException e) {
+            assertTrue(e.getMessage().contains("555"));
+        }
     }
 
     public void testClearFormatting() {
@@ -431,4 +495,13 @@ public final class TestXSSFRichTextString extends TestCase {
         assertNotNull(rt.getFontOfFormattingRun(2));
         assertEquals(9, rt.getLengthOfFormattingRun(2));
     }
+
+    public void testToString() {
+        XSSFRichTextString rt = new XSSFRichTextString("Apache POI");
+        assertNotNull(rt.toString());
+        
+        // TODO: normally toString() should never return null, should we adjust this?
+        rt = new XSSFRichTextString();
+        assertNull(rt.toString());
+    }
 }