Support for IRR() function, see Bugzilla 50409. Includes fix for Bugzilla 50437

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1044370 13f79535-47bb-0310-9956-ffa450edef68

10 files changed, 373 insertions, 66 deletions

diff --git a/src/documentation/content/xdocs/index.xml b/src/documentation/content/xdocs/index.xml
index 5b77ebaa1f..2db376ab2d 100644
--- a/src/documentation/content/xdocs/index.xml
+++ b/src/documentation/content/xdocs/index.xml
@@ -35,7 +35,7 @@
     <section><title>29 October 2010 - POI 3.7 available</title>
      <p>The Apache POI team is pleased to announce the release of 3.7. This includes a large number of bug fixes, and some
         enhancements (especially text extraction). See the
-        <link href="http://www.apache.org/dist/poi/release/bin/RELEASE-NOTES.txt">full release notes</link> for more details.
+        <link href="http://www.apache.org/dist/poi/release/bin/RELEASE_NOTES.txt">full release notes</link> for more details.
       </p>
       <p>A full list of changes is available in the <link href="changes.html">change log</link>. 
       People interested should also follow the <link href="mailinglists.html">dev mailing list</link> to track further progress.</p>
diff --git a/src/documentation/content/xdocs/status.xml b/src/documentation/content/xdocs/status.xml
index 7854a2adc7..f120102386 100644
--- a/src/documentation/content/xdocs/status.xml
+++ b/src/documentation/content/xdocs/status.xml
@@ -34,8 +34,10 @@
 
     <changes>
         <release version="3.8-beta1" date="2010-??-??">
+           <action dev="POI-DEVELOPERS" type="add">50437 - Support passing ranges to NPV()</action>
+           <action dev="POI-DEVELOPERS" type="add">50409 - Added implementation for IRR()</action>
            <action dev="poi-developers" type="add">47405 - Improved performance of RowRecordsAggregate.getStartRowNumberForBlock / getEndRowNumberForBlock</action>
-           <action dev="poi-developers" type="add">50315 - Avoid crashing Excel when sorting XSSFSheet autofilter</action>
+           <action dev="poi-developers" type="fix">50315 - Avoid crashing Excel when sorting XSSFSheet autofilter</action>
            <action dev="poi-developers" type="add">50076 - Allow access from XSSFReader to sheet comments and headers/footers</action>
            <action dev="poi-developers" type="add">50076 - Refactor XSSFEventBasedExcelExtractor to make it easier for you to have control over outputting the cell contents</action>
            <action dev="poi-developers" type="fix">50258 - avoid corruption of XSSFWorkbook after applying XSSFRichTextRun#applyFont</action>
diff --git a/src/java/org/apache/poi/ss/formula/eval/FunctionEval.java b/src/java/org/apache/poi/ss/formula/eval/FunctionEval.java
index 85957dad48..01fc068fe9 100644
--- a/src/java/org/apache/poi/ss/formula/eval/FunctionEval.java
+++ b/src/java/org/apache/poi/ss/formula/eval/FunctionEval.java
@@ -100,6 +100,7 @@ public final class FunctionEval {
 		retval[58] = FinanceFunction.NPER;
 		retval[59] = FinanceFunction.PMT;
 
+		retval[62] = new Irr();
 		retval[63] = NumericFunction.RAND;
 		retval[64] = new Match();
 		retval[65] = DateFunc.instance;
diff --git a/src/java/org/apache/poi/ss/formula/functions/AggregateFunction.java b/src/java/org/apache/poi/ss/formula/functions/AggregateFunction.java
index a8cff4e130..7a047dc70a 100644
--- a/src/java/org/apache/poi/ss/formula/functions/AggregateFunction.java
+++ b/src/java/org/apache/poi/ss/formula/functions/AggregateFunction.java
@@ -67,7 +67,7 @@ public abstract class AggregateFunction extends MultiOperandNumericFunction {
 			return new NumberEval(result);
 		}
 	}
-	private static final class ValueCollector extends MultiOperandNumericFunction {
+	static final class ValueCollector extends MultiOperandNumericFunction {
 		private static final ValueCollector instance = new ValueCollector();
 		public ValueCollector() {
 			super(false, false);
diff --git a/src/java/org/apache/poi/ss/formula/functions/FinanceLib.java b/src/java/org/apache/poi/ss/formula/functions/FinanceLib.java
index d61e7e020f..2a10fc9c39 100644
--- a/src/java/org/apache/poi/ss/formula/functions/FinanceLib.java
+++ b/src/java/org/apache/poi/ss/formula/functions/FinanceLib.java
@@ -56,7 +56,7 @@ package org.apache.poi.ss.formula.functions;
  * ny + p + f=0                            ...{when r=0}
  * </pre>
  */
-final class FinanceLib {
+public final class FinanceLib {
 
     private FinanceLib() {
         // no instances of this class
diff --git a/src/java/org/apache/poi/ss/formula/functions/Irr.java b/src/java/org/apache/poi/ss/formula/functions/Irr.java
new file mode 100644
index 0000000000..27f7232eb2
--- /dev/null
+++ b/src/java/org/apache/poi/ss/formula/functions/Irr.java
@@ -0,0 +1,120 @@
+/* ====================================================================
+   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.
+==================================================================== */
+
+package org.apache.poi.ss.formula.functions;
+
+import org.apache.poi.ss.formula.eval.*;
+
+/**
+ * Calculates the internal rate of return.
+ *
+ * Syntax is IRR(values) or IRR(values,guess)
+ *
+ * @author Marcel May
+ * @author Yegor Kozlov
+ *
+ * @see <a href="http://en.wikipedia.org/wiki/Internal_rate_of_return#Numerical_solution">Wikipedia on IRR</a>
+ * @see <a href="http://office.microsoft.com/en-us/excel-help/irr-HP005209146.aspx">Excel IRR</a>
+ */
+public final class Irr implements Function {
+
+
+    public ValueEval evaluate(final ValueEval[] args, final int srcRowIndex, final int srcColumnIndex) {
+        if(args.length == 0 || args.length > 2) {
+            // Wrong number of arguments
+            return ErrorEval.VALUE_INVALID;
+        }
+
+        try {
+            double[] values = AggregateFunction.ValueCollector.collectValues(args[0]);
+            double guess;
+            if(args.length == 2) {
+                guess = NumericFunction.singleOperandEvaluate(args[1], srcRowIndex, srcColumnIndex);
+            } else {
+                guess = 0.1d;
+            }
+            double result = irr(values, guess);
+            NumericFunction.checkValue(result);
+            return new NumberEval(result);
+        } catch (EvaluationException e){
+            return e.getErrorEval();
+        }
+    }
+
+    /**
+     * Computes the internal rate of return using an estimated irr of 10 percent.
+     *
+     * @param income the income values.
+     * @return the irr.
+     */
+    public static double irr(double[] income) {
+        return irr(income, 0.1d);
+    }
+
+
+    /**
+     * Calculates IRR using the Newton-Raphson Method.
+     * <p>
+     * Starting with the guess, the method cycles through the calculation until the result
+     * is accurate within 0.00001 percent. If IRR can't find a result that works
+     * after 20 tries, the Double.NaN<> is returned.
+     * </p>
+     * <p>
+     *   The implementation is inspired by the NewtonSolver from the Apache Commons-Math library,
+     *   @see {http://commons.apache.org/}
+     * </p>
+     *
+     * @param values        the income values.
+     * @param guess         the initial guess of irr.
+     * @return the irr value. The method returns <code>Double.NaN</code>
+     *  if the maximum iteration count is exceeded
+     *
+     * @see {http://en.wikipedia.org/wiki/Internal_rate_of_return#Numerical_solution}
+     * @see {http://en.wikipedia.org/wiki/Newton%27s_method}
+     */
+    public static double irr(double[] values, double guess) {
+        int maxIterationCount = 20;
+        double absoluteAccuracy = 1E-7;
+
+        double x0 = guess;
+        double x1;
+
+        int i = 0;
+        while (i < maxIterationCount) {
+
+            // the value of the function (NPV) and its derivate can be calculated in the same loop
+            double fValue = 0;
+            double fDerivative = 0;
+            for (int k = 0; k < values.length; k++) {
+                fValue += values[k] / Math.pow(1.0 + x0, k);
+                fDerivative += -k * values[k] / Math.pow(1.0 + x0, k + 1);
+            }
+
+            // the essense of the Newton-Raphson Method
+            x1 = x0 - fValue/fDerivative;
+
+            if (Math.abs(x1 - x0) <= absoluteAccuracy) {
+                return x1;
+            }
+
+            x0 = x1;
+            ++i;
+        }
+        // maximum number of iterations is exceeded
+        return Double.NaN;
+    }
+}
diff --git a/src/java/org/apache/poi/ss/formula/functions/Npv.java b/src/java/org/apache/poi/ss/formula/functions/Npv.java
index 3d86ad6dd6..8ca7f8555c 100644
--- a/src/java/org/apache/poi/ss/formula/functions/Npv.java
+++ b/src/java/org/apache/poi/ss/formula/functions/Npv.java
@@ -17,11 +17,14 @@
 
 package org.apache.poi.ss.formula.functions;
 
+import org.apache.poi.ss.formula.TwoDEval;
 import org.apache.poi.ss.formula.eval.ErrorEval;
 import org.apache.poi.ss.formula.eval.EvaluationException;
 import org.apache.poi.ss.formula.eval.NumberEval;
 import org.apache.poi.ss.formula.eval.ValueEval;
 
+import java.util.Arrays;
+
 /**
  * Calculates the net present value of an investment by using a discount rate
  * and a series of future payments (negative values) and income (positive
@@ -30,78 +33,27 @@ import org.apache.poi.ss.formula.eval.ValueEval;
  * income.
  *
  * @author SPetrakovsky
+ * @author Marcel May
  */
-public final class Npv implements Function2Arg, Function3Arg, Function4Arg {
-
-
-	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1) {
-		double result;
-		try {
-			double rate = NumericFunction.singleOperandEvaluate(arg0, srcRowIndex, srcColumnIndex);
-			double d1 = NumericFunction.singleOperandEvaluate(arg1, srcRowIndex, srcColumnIndex);
-			result = evaluate(rate, d1);
-			NumericFunction.checkValue(result);
-		} catch (EvaluationException e) {
-			return e.getErrorEval();
-		}
-		return new NumberEval(result);
-	}
-	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1,
-			ValueEval arg2) {
-		double result;
-		try {
-			double rate = NumericFunction.singleOperandEvaluate(arg0, srcRowIndex, srcColumnIndex);
-			double d1 = NumericFunction.singleOperandEvaluate(arg1, srcRowIndex, srcColumnIndex);
-			double d2 = NumericFunction.singleOperandEvaluate(arg2, srcRowIndex, srcColumnIndex);
-			result = evaluate(rate, d1, d2);
-			NumericFunction.checkValue(result);
-		} catch (EvaluationException e) {
-			return e.getErrorEval();
-		}
-		return new NumberEval(result);
-	}
-	public ValueEval evaluate(int srcRowIndex, int srcColumnIndex, ValueEval arg0, ValueEval arg1,
-			ValueEval arg2, ValueEval arg3) {
-		double result;
-		try {
-			double rate = NumericFunction.singleOperandEvaluate(arg0, srcRowIndex, srcColumnIndex);
-			double d1 = NumericFunction.singleOperandEvaluate(arg1, srcRowIndex, srcColumnIndex);
-			double d2 = NumericFunction.singleOperandEvaluate(arg2, srcRowIndex, srcColumnIndex);
-			double d3 = NumericFunction.singleOperandEvaluate(arg3, srcRowIndex, srcColumnIndex);
-			result = evaluate(rate, d1, d2, d3);
-			NumericFunction.checkValue(result);
-		} catch (EvaluationException e) {
-			return e.getErrorEval();
-		}
-		return new NumberEval(result);
-	}
+public final class Npv implements Function {
 
 	public ValueEval evaluate(ValueEval[] args, int srcRowIndex, int srcColumnIndex) {
 		int nArgs = args.length;
-		if (nArgs<2) {
+		if (nArgs < 2) {
 			return ErrorEval.VALUE_INVALID;
 		}
-		int np = nArgs-1;
-		double[] ds = new double[np];
-		double result;
-		try {
+
+        try {
 			double rate = NumericFunction.singleOperandEvaluate(args[0], srcRowIndex, srcColumnIndex);
-			for (int i = 0; i < ds.length; i++) {
-				ds[i] =  NumericFunction.singleOperandEvaluate(args[i+1], srcRowIndex, srcColumnIndex);
-			}
-			result = evaluate(rate, ds);
+            // convert tail arguments into an array of doubles
+            ValueEval[] vargs = Arrays.copyOfRange(args, 1 , args.length);
+            double[] values = AggregateFunction.ValueCollector.collectValues(vargs);
+
+            double result = FinanceLib.npv(rate, values);
 			NumericFunction.checkValue(result);
+            return new NumberEval(result);
 		} catch (EvaluationException e) {
 			return e.getErrorEval();
 		}
-		return new NumberEval(result);
-	}
-
-	private static double evaluate(double rate, double...ds) {
-		double sum = 0;
-		for (int i = 0; i < ds.length; i++) {
-			sum += ds[i] / Math.pow(rate + 1, i);
-		}
-		return sum;
 	}
 }
diff --git a/src/testcases/org/apache/poi/ss/formula/functions/TestIrr.java b/src/testcases/org/apache/poi/ss/formula/functions/TestIrr.java
new file mode 100644
index 0000000000..7606d3fefa
--- /dev/null
+++ b/src/testcases/org/apache/poi/ss/formula/functions/TestIrr.java
@@ -0,0 +1,128 @@
+/* ====================================================================
+   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.
+==================================================================== */
+
+package org.apache.poi.ss.formula.functions;
+
+import junit.framework.TestCase;
+import junit.framework.AssertionFailedError;
+import org.apache.poi.hssf.usermodel.*;
+import org.apache.poi.hssf.HSSFTestDataSamples;
+import org.apache.poi.ss.usermodel.CellValue;
+
+/**
+ * Tests for {@link Irr}
+ *
+ * @author Marcel May
+ */
+public final class TestIrr extends TestCase {
+
+    public void testIrr() {
+        // http://en.wikipedia.org/wiki/Internal_rate_of_return#Example
+        double[] incomes = {-4000d, 1200d, 1410d, 1875d, 1050d};
+        double irr = Irr.irr(incomes);
+        double irrRounded = Math.round(irr * 1000d) / 1000d;
+        assertEquals("irr", 0.143d, irrRounded);
+
+        // http://www.techonthenet.com/excel/formulas/irr.php
+        incomes = new double[]{-7500d, 3000d, 5000d, 1200d, 4000d};
+        irr = Irr.irr(incomes);
+        irrRounded = Math.round(irr * 100d) / 100d;
+        assertEquals("irr", 0.28d, irrRounded);
+
+        incomes = new double[]{-10000d, 3400d, 6500d, 1000d};
+        irr = Irr.irr(incomes);
+        irrRounded = Math.round(irr * 100d) / 100d;
+        assertEquals("irr", 0.05, irrRounded);
+
+        incomes = new double[]{100d, -10d, -110d};
+        irr = Irr.irr(incomes);
+        irrRounded = Math.round(irr * 100d) / 100d;
+        assertEquals("irr", 0.1, irrRounded);
+
+        incomes = new double[]{-70000d, 12000, 15000};
+        irr = Irr.irr(incomes, -0.1);
+        irrRounded = Math.round(irr * 100d) / 100d;
+        assertEquals("irr", -0.44, irrRounded);
+    }
+
+    public void testEvaluateInSheet() {
+        HSSFWorkbook wb = new HSSFWorkbook();
+        HSSFSheet sheet = wb.createSheet("Sheet1");
+        HSSFRow row = sheet.createRow(0);
+
+        row.createCell(0).setCellValue(-4000d);
+        row.createCell(1).setCellValue(1200d);
+        row.createCell(2).setCellValue(1410d);
+        row.createCell(3).setCellValue(1875d);
+        row.createCell(4).setCellValue(1050d);
+
+        HSSFCell cell = row.createCell(5);
+        cell.setCellFormula("IRR(A1:E1)");
+
+        HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+        fe.clearAllCachedResultValues();
+        fe.evaluateFormulaCell(cell);
+        double res = cell.getNumericCellValue();
+        assertEquals(0.143d, Math.round(res * 1000d) / 1000d);
+    }
+
+    public void testIrrFromSpreadsheet(){
+        HSSFWorkbook wb = HSSFTestDataSamples.openSampleWorkbook("IrrNpvTestCaseData.xls");
+        HSSFSheet sheet = wb.getSheet("IRR-NPV");
+        HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+        StringBuffer failures = new StringBuffer();
+        int failureCount = 0;
+        // TODO YK: Formulas in rows 16 and 17 operate with ArrayPtg which isn't yet supported
+        // FormulaEvaluator as of r1041407 throws "Unexpected ptg class (org.apache.poi.ss.formula.ptg.ArrayPtg)"
+        for(int rownum = 9; rownum <= 15; rownum++){
+            HSSFRow row = sheet.getRow(rownum);
+            HSSFCell cellA = row.getCell(0);
+            try {
+                CellValue cv = fe.evaluate(cellA);
+                assertFormulaResult(cv, cellA);
+            } catch (Throwable e){
+                if(failures.length() > 0) failures.append('\n');
+                failures.append("Row[" + (cellA.getRowIndex() + 1)+ "]: " + cellA.getCellFormula() + " ");
+                failures.append(e.getMessage());
+                failureCount++;
+            }
+
+            HSSFCell cellC = row.getCell(2); //IRR-NPV relationship: NPV(IRR(values), values) = 0
+            try {
+                CellValue cv = fe.evaluate(cellC);
+                assertEquals(0, cv.getNumberValue(), 0.0001);  // should agree within 0.01%
+            } catch (Throwable e){
+                if(failures.length() > 0) failures.append('\n');
+                failures.append("Row[" + (cellC.getRowIndex() + 1)+ "]: " + cellC.getCellFormula() + " ");
+                failures.append(e.getMessage());
+                failureCount++;
+            }
+        }
+
+        if(failures.length() > 0) {
+            throw new AssertionFailedError(failureCount + " IRR assertions failed:\n" + failures.toString());
+        }
+
+    }
+
+    private static void assertFormulaResult(CellValue cv, HSSFCell cell){
+        double actualValue = cv.getNumberValue();
+        double expectedValue = cell.getNumericCellValue(); // cached formula result calculated by Excel
+        assertEquals("Invalid formula result: " + cv.toString(), HSSFCell.CELL_TYPE_NUMERIC, cv.getCellType());
+        assertEquals(expectedValue, actualValue, 1E-4); // should agree within 0.01%
+    }
+}
diff --git a/src/testcases/org/apache/poi/ss/formula/functions/TestNpv.java b/src/testcases/org/apache/poi/ss/formula/functions/TestNpv.java
new file mode 100644
index 0000000000..247138a4b6
--- /dev/null
+++ b/src/testcases/org/apache/poi/ss/formula/functions/TestNpv.java
@@ -0,0 +1,104 @@
+/* ====================================================================
+   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.
+==================================================================== */
+
+package org.apache.poi.ss.formula.functions;
+
+import junit.framework.TestCase;
+import junit.framework.AssertionFailedError;
+import org.apache.poi.hssf.usermodel.*;
+import org.apache.poi.hssf.HSSFTestDataSamples;
+import org.apache.poi.ss.usermodel.Cell;
+import org.apache.poi.ss.usermodel.Row;
+import org.apache.poi.ss.usermodel.CellValue;
+
+/**
+ * Tests for {@link Npv}
+ *
+ * @author Marcel May
+ * @see <a href="http://office.microsoft.com/en-us/excel-help/npv-HP005209199.aspx">Excel Help</a>
+ */
+public final class TestNpv extends TestCase {
+
+    public void testEvaluateInSheetExample2() {
+        HSSFWorkbook wb = new HSSFWorkbook();
+        HSSFSheet sheet = wb.createSheet("Sheet1");
+        HSSFRow row = sheet.createRow(0);
+
+        sheet.createRow(1).createCell(0).setCellValue(0.08d);
+        sheet.createRow(2).createCell(0).setCellValue(-40000d);
+        sheet.createRow(3).createCell(0).setCellValue(8000d);
+        sheet.createRow(4).createCell(0).setCellValue(9200d);
+        sheet.createRow(5).createCell(0).setCellValue(10000d);
+        sheet.createRow(6).createCell(0).setCellValue(12000d);
+        sheet.createRow(7).createCell(0).setCellValue(14500d);
+
+        HSSFCell cell = row.createCell(8);
+        HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+
+        // Enumeration
+        cell.setCellFormula("NPV(A2, A4,A5,A6,A7,A8)+A3");
+        fe.clearAllCachedResultValues();
+        fe.evaluateFormulaCell(cell);
+        double res = cell.getNumericCellValue();
+        assertEquals(1922.06d, Math.round(res * 100d) / 100d);
+
+        // Range
+        cell.setCellFormula("NPV(A2, A4:A8)+A3");
+
+        fe.clearAllCachedResultValues();
+        fe.evaluateFormulaCell(cell);
+        res = cell.getNumericCellValue();
+        assertEquals(1922.06d, Math.round(res * 100d) / 100d);
+    }
+
+    /**
+     * evaluate formulas with NPV and compare the result with
+     * the cached formula result pre-calculated by Excel
+     */
+    public void testNpvFromSpreadsheet(){
+        HSSFWorkbook wb = HSSFTestDataSamples.openSampleWorkbook("IrrNpvTestCaseData.xls");
+        HSSFSheet sheet = wb.getSheet("IRR-NPV");
+        HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+        StringBuffer failures = new StringBuffer();
+        int failureCount = 0;
+        // TODO YK: Formulas in rows 16 and 17 operate with ArrayPtg which isn't yet supported
+        // FormulaEvaluator as of r1041407 throws "Unexpected ptg class (org.apache.poi.ss.formula.ptg.ArrayPtg)"
+        for(int rownum = 9; rownum <= 15; rownum++){
+            HSSFRow row = sheet.getRow(rownum);
+            HSSFCell cellB = row.getCell(1);
+            try {
+                CellValue cv = fe.evaluate(cellB);
+                assertFormulaResult(cv, cellB);
+            } catch (Throwable e){
+                if(failures.length() > 0) failures.append('\n');
+                failures.append("Row[" + (cellB.getRowIndex() + 1)+ "]: " + cellB.getCellFormula() + " ");
+                failures.append(e.getMessage());
+                failureCount++;
+            }
+        }
+
+        if(failures.length() > 0) {
+            throw new AssertionFailedError(failureCount + " IRR evaluations failed:\n" + failures.toString());
+        }
+    }
+
+    private static void assertFormulaResult(CellValue cv, HSSFCell cell){
+        double actualValue = cv.getNumberValue();
+        double expectedValue = cell.getNumericCellValue(); // cached formula result calculated by Excel
+        assertEquals(expectedValue, actualValue, 1E-4); // should agree within 0.01%
+    }
+}
diff --git a/test-data/spreadsheet/IrrNpvTestCaseData.xls b/test-data/spreadsheet/IrrNpvTestCaseData.xls
new file mode 100644
index 0000000000..667493b463
--- /dev/null
+++ b/test-data/spreadsheet/IrrNpvTestCaseData.xls