main/src/test/java/org/apache/poi/ss/formula/eval/TestFormulasFromSpreadsheet.java

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   this work for additional information regarding copyright ownership.
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package org.apache.poi.ss.formula.eval;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.junit.jupiter.api.Assertions.fail;

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;
import java.util.stream.Stream;

import org.apache.poi.hssf.HSSFTestDataSamples;
import org.apache.poi.hssf.usermodel.HSSFFormulaEvaluator;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.formula.functions.TestMathX;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellType;
import org.apache.poi.ss.usermodel.CellValue;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.util.LocaleUtil;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.Arguments;
import org.junit.jupiter.params.provider.MethodSource;

/**
 * Tests formulas and operators as loaded from a test data spreadsheet.<p>
 * This class does not test implementors of <tt>Function</tt> and <tt>OperationEval</tt> in
 * isolation.  Much of the evaluation engine (i.e. <tt>HSSFFormulaEvaluator</tt>, ...) gets
 * exercised as well.  Tests for bug fixes and specific/tricky behaviour can be found in the
 * corresponding test class (<tt>TestXxxx</tt>) of the target (<tt>Xxxx</tt>) implementor,
 * where execution can be observed more easily.
 */
public final class TestFormulasFromSpreadsheet {

    private static HSSFWorkbook workbook;
    private static Sheet sheet;
    private static HSSFFormulaEvaluator evaluator;
    private static Locale userLocale;

    /**
	 * This class defines constants for navigating around the test data spreadsheet used for these tests.
	 */
	private interface SS {

		/**
		 * Name of the test spreadsheet (found in the standard test data folder)
		 */
		String FILENAME = "FormulaEvalTestData.xls";
		/**
		 * Row (zero-based) in the test spreadsheet where the operator examples start.
		 */
		int START_OPERATORS_ROW_INDEX = 22; // Row '23'
		/**
		 * Row (zero-based) in the test spreadsheet where the function examples start.
		 */
		int START_FUNCTIONS_ROW_INDEX = 95; // Row '96'
		/**
		 * Index of the column that contains the function names
		 */
		int COLUMN_INDEX_FUNCTION_NAME = 1; // Column 'B'

		/**
		 * Used to indicate when there are no more functions left
		 */
		String FUNCTION_NAMES_END_SENTINEL = "<END-OF-FUNCTIONS>";

		/**
		 * Index of the column where the test values start (for each function)
		 */
		short COLUMN_INDEX_FIRST_TEST_VALUE = 3; // Column 'D'

		/**
		 * Each function takes 4 rows in the test spreadsheet
		 */
		int NUMBER_OF_ROWS_PER_FUNCTION = 4;
	}

    @AfterAll
    public static void closeResource() throws Exception {
        LocaleUtil.setUserLocale(userLocale);
        workbook.close();
    }

    public static Stream<Arguments> data() {
        // Function "Text" uses custom-formats which are locale specific
        // can't set the locale on a per-testrun execution, as some settings have been
        // already set, when we would try to change the locale by then
        userLocale = LocaleUtil.getUserLocale();
        LocaleUtil.setUserLocale(Locale.ROOT);

        workbook = HSSFTestDataSamples.openSampleWorkbook(SS.FILENAME);
        sheet = workbook.getSheetAt( 0 );
        evaluator = new HSSFFormulaEvaluator(workbook);

        List<Arguments> data = new ArrayList<>();

        processFunctionGroup(data, SS.START_OPERATORS_ROW_INDEX);
        processFunctionGroup(data, SS.START_FUNCTIONS_ROW_INDEX);
        // example for debugging individual functions/operators:
        // processFunctionGroup(data, SS.START_OPERATORS_ROW_INDEX, "ConcatEval");
        // processFunctionGroup(data, SS.START_FUNCTIONS_ROW_INDEX, "Text");

        return data.stream();
    }

    /**
     * @param startRowIndex row index in the spreadsheet where the first function/operator is found
     * Typically pass <code>null</code> to test all functions
     */
    private static void processFunctionGroup(List<Arguments> data, int startRowIndex) {
        for (int rowIndex = startRowIndex; true; rowIndex += SS.NUMBER_OF_ROWS_PER_FUNCTION) {
            Row r = sheet.getRow(rowIndex);
            String targetFunctionName = getTargetFunctionName(r);
            assertNotNull(targetFunctionName, "Test spreadsheet cell empty on row ("
                    + (rowIndex+1) + "). Expected function name or '"
                    + SS.FUNCTION_NAMES_END_SENTINEL + "'");
            if(targetFunctionName.equals(SS.FUNCTION_NAMES_END_SENTINEL)) {
                // found end of functions list
                break;
            }

            // expected results are on the row below
            Row expectedValuesRow = sheet.getRow(rowIndex + 1);
            int missingRowNum = rowIndex + 2; //+1 for 1-based, +1 for next row
            assertNotNull(expectedValuesRow, "Missing expected values row for function '"
                    + targetFunctionName + " (row " + missingRowNum + ")");

            data.add(Arguments.of(targetFunctionName, rowIndex, rowIndex + 1));
        }
    }

    @ParameterizedTest
    @MethodSource("data")
    void processFunctionRow(String targetFunctionName, int formulasRowIdx, int expectedValuesRowIdx) {
        Row formulasRow = sheet.getRow(formulasRowIdx);
        Row expectedValuesRow = sheet.getRow(expectedValuesRowIdx);

        short endcolnum = formulasRow.getLastCellNum();

       // iterate across the row for all the evaluation cases
       for (int colnum=SS.COLUMN_INDEX_FIRST_TEST_VALUE; colnum < endcolnum; colnum++) {
           Cell c = formulasRow.getCell(colnum);
           if (c == null || c.getCellType() != CellType.FORMULA) {
               continue;
           }

           CellValue actValue = evaluator.evaluate(c);
           Cell expValue = (expectedValuesRow == null) ? null : expectedValuesRow.getCell(colnum);

           String msg = String.format(Locale.ROOT, "Function '%s': Formula: %s @ %d:%d"
                   , targetFunctionName, c.getCellFormula(), formulasRow.getRowNum(), colnum);

           assertNotNull(expValue, msg + " - Bad setup data expected value is null");
           assertNotNull(actValue, msg + " - actual value was null");

           final CellType cellType = expValue.getCellType();
           switch (cellType) {
               case BLANK:
                   assertEquals(CellType.BLANK, actValue.getCellType(), msg);
                   break;
               case BOOLEAN:
                   assertEquals(CellType.BOOLEAN, actValue.getCellType(), msg);
                   assertEquals(expValue.getBooleanCellValue(), actValue.getBooleanValue(), msg);
                   break;
               case ERROR:
                   assertEquals(CellType.ERROR, actValue.getCellType(), msg);
                   assertEquals(ErrorEval.getText(expValue.getErrorCellValue()), ErrorEval.getText(actValue.getErrorValue()), msg);
                   break;
               case FORMULA: // will never be used, since we will call method after formula evaluation
                   fail("Cannot expect formula as result of formula evaluation: " + msg);
               case NUMERIC:
                   assertEquals(CellType.NUMERIC, actValue.getCellType(), msg);
                   TestMathX.assertDouble(msg, expValue.getNumericCellValue(), actValue.getNumberValue(), TestMathX.POS_ZERO, TestMathX.DIFF_TOLERANCE_FACTOR);
                   break;
               case STRING:
                   assertEquals(CellType.STRING, actValue.getCellType(), msg);
                   assertEquals(expValue.getRichStringCellValue().getString(), actValue.getStringValue(), msg);
                   break;
               default:
                   fail("Unexpected cell type: " + cellType);
           }
       }
   }
	/**
	 * @return <code>null</code> if cell is missing, empty or blank
	 */
	private static String getTargetFunctionName(Row r) {
		if(r == null) {
			System.err.println("Warning - given null row, can't figure out function name");
			return null;
		}
		Cell cell = r.getCell(SS.COLUMN_INDEX_FUNCTION_NAME);
		if(cell == null) {
			System.err.println("Warning - Row " + r.getRowNum() + " has no cell " + SS.COLUMN_INDEX_FUNCTION_NAME + ", can't figure out function name");
			return null;
		}

        CellType ct = cell.getCellType();
        assertTrue(ct == CellType.BLANK || ct == CellType.STRING,
            "Bad cell type for 'function name' column: (" + cell.getCellType() + ") row (" + (r.getRowNum() +1) + ")");

        return (ct == CellType.STRING) ? cell.getRichStringCellValue().getString() : null;
	}
}