The `WORKDAY()` function accepts 2 "static" arguments that could be passed as arrays; but also accepts a set of trailing date arguments that are accepted as an array by the splat operator. Only the first two arguments should be tested for returning array values; but the logic still needs to work with the full argument set.

Provide a separate "subset" method in the `ArrayEnabled` Trait, that allows a subset of arguments to be tested for array returns.

Set up basic tests for `WORKDAY()`

src/PhpSpreadsheet/Calculation/ArrayEnabled.php

@@ -37,6 +37,27 @@ trait ArrayEnabled
         self::initialiseHelper($arguments);
         $arguments = self::$arrayArgumentHelper->arguments();
 
+        return self::processArguments($method, ...$arguments);
+    }
+
+    /**
+     * @param mixed ...$arguments
+     */
+    protected static function evaluateArrayArgumentsSubset(callable $method, int $limit, ...$arguments): array
+    {
+        self::initialiseHelper(array_slice($arguments, 0, $limit));
+        $trailingArguments = array_slice($arguments, $limit);
+        $arguments = self::$arrayArgumentHelper->arguments();
+        $arguments = array_merge($arguments, $trailingArguments);
+
+        return self::processArguments($method, ...$arguments);
+    }
+
+    /**
+     * @param mixed ...$arguments
+     */
+    private static function processArguments(callable $method, ...$arguments): array
+    {
         if (self::$arrayArgumentHelper->hasArrayArgument() === false) {
             return [$method(...$arguments)];
         }

src/PhpSpreadsheet/Calculation/DateTimeExcel/WorkDay.php

@@ -151,6 +151,7 @@ class WorkDay
             --$endDate;
             //    Adjust the calculated end date if it falls over a weekend
             $endDow = self::getWeekDay($endDate, 3);
+            /** int $endDoW */
             if ($endDow >= 5) {
                 $endDate += 4 - $endDow;
             }
@@ -183,6 +184,7 @@ class WorkDay
             }
             //    Adjust the calculated end date if it falls over a weekend
             $endDoW = self::getWeekDay($endDate, 3);
+            /** int $endDoW */
             if ($endDoW >= 5) {
                 $endDate += -$endDoW + 4;
             }

tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/WorkDayTest.php

@@ -2,6 +2,8 @@
 
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
+use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
+
 class WorkDayTest extends AllSetupTeardown
 {
     /**
@@ -49,4 +51,33 @@ class WorkDayTest extends AllSetupTeardown
     {
         return require 'tests/data/Calculation/DateTime/WORKDAY.php';
     }
+
+    /**
+     * @dataProvider providerWorkDayArray
+     */
+    public function testWorkDayArray(array $expectedResult, string $startDate, string $endDays, ?string $holidays): void
+    {
+        $calculation = Calculation::getInstance();
+
+        if ($holidays === null) {
+            $formula = "=WORKDAY({$startDate}, {$endDays})";
+        } else {
+            $formula = "=WORKDAY({$startDate}, {$endDays}, {$holidays})";
+        }
+        $result = $calculation->_calculateFormulaValue($formula);
+        self::assertEqualsWithDelta($expectedResult, $result, 1.0e-14);
+    }
+
+    public function providerWorkDayArray(): array
+    {
+        return [
+            'row vector #1' => [[[44595, 44596, 44599]], '{"2022-02-01", "2022-02-02", "2022-02-03"}', '2', null],
+            'column vector #1' => [[[44595], [44596], [44599]], '{"2022-02-01"; "2022-02-02"; "2022-02-03"}', '2', null],
+            'matrix #1' => [[[44595, 44596], [44599, 44600]], '{"2022-02-01", "2022-02-02"; "2022-02-03", "2022-02-04"}', '2', null],
+            'row vector #2' => [[[44595, 44596]], '"2022-02-01"', '{2, 3}', null],
+            'column vector #2' => [[[44595], [44596]], '"2022-02-01"', '{2; 3}', null],
+            'row vector with Holiday' => [[[44596, 44599]], '"2022-02-01"', '{2, 3}', '{"2022-02-02"}'],
+            'row vector with Holidays' => [[[44599, 44600]], '"2022-02-01"', '{2, 3}', '{"2022-02-02", "2022-02-03"}'],
+        ];
+    }
 }