diff --git a/src/PhpSpreadsheet/Calculation/Calculation.php b/src/PhpSpreadsheet/Calculation/Calculation.php
index 98f36cde0b..c88656b4a0 100644
--- a/src/PhpSpreadsheet/Calculation/Calculation.php
+++ b/src/PhpSpreadsheet/Calculation/Calculation.php
@@ -4250,7 +4250,7 @@ private function internalParseFormula($formula, ?Cell $cell = null)
                     } elseif ($expectedArgumentCount != '*') {
                         $isOperandOrFunction = preg_match('/(\d*)([-+,])(\d*)/', $expectedArgumentCount, $argMatch);
                         self::doNothing($isOperandOrFunction);
-                        switch ($argMatch[2]) {
+                        switch ($argMatch[2] ?? '') {
                             case '+':
                                 if ($argumentCount < $argMatch[1]) {
                                     $argumentCountError = true;
diff --git a/src/PhpSpreadsheet/Reader/Xlsx.php b/src/PhpSpreadsheet/Reader/Xlsx.php
index 310fef74f8..ef2f48af0a 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx.php
@@ -134,7 +134,7 @@ private function loadZip(string $filename, string $ns = '', bool $replaceUnclose
         if ($replaceUnclosedBr) {
             $contents = str_replace('<br>', '<br/>', $contents);
         }
-        $rels = simplexml_load_string(
+        $rels = @simplexml_load_string(
             $this->getSecurityScannerOrThrow()->scan($contents),
             'SimpleXMLElement',
             Settings::getLibXmlLoaderOptions(),
diff --git a/tests/PhpSpreadsheetTests/Calculation/DefinedNamesCalculationTest.php b/tests/PhpSpreadsheetTests/Calculation/DefinedNamesCalculationTest.php
index d0a5aacb6b..4f450f57c5 100644
--- a/tests/PhpSpreadsheetTests/Calculation/DefinedNamesCalculationTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/DefinedNamesCalculationTest.php
@@ -71,7 +71,7 @@ public function testNamedFormulaeCalculationsWithAdjustedRateValue(string $cellA
         self::assertSame($expectedValue, $calculatedCellValue, "Failed calculation for cell {$cellAddress}");
     }
 
-    public function namedRangeCalculationTest1(): array
+    public static function namedRangeCalculationTest1(): array
     {
         return [
             ['C4', 56.25],
@@ -84,7 +84,7 @@ public function namedRangeCalculationTest1(): array
         ];
     }
 
-    public function namedRangeCalculationTest2(): array
+    public static function namedRangeCalculationTest2(): array
     {
         return [
             ['C4', 93.75],
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DAverageTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DAverageTest.php
index b1756b2a8e..777469525c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DAverageTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DAverageTest.php
@@ -35,12 +35,12 @@ public function testDAverageAsWorksheetFormula($expectedResult, array $database,
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDAverage(): array
+    public static function providerDAverage(): array
     {
         return [
             [
                 12,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree', 'Height'],
@@ -49,7 +49,7 @@ public function providerDAverage(): array
             ],
             [
                 268333.333333333333,
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Quarter', 'Sales Rep.'],
@@ -58,7 +58,7 @@ public function providerDAverage(): array
             ],
             [
                 372500,
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Quarter', 'Area'],
@@ -67,25 +67,25 @@ public function providerDAverage(): array
             ],
             'numeric column, in this case referring to age' => [
                 13,
-                $this->database1(),
+                self::database1(),
                 3,
-                $this->database1(),
+                self::database1(),
             ],
             'null field' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
             'field unknown column' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 'xyz',
-                $this->database1(),
+                self::database1(),
             ],
             'multiple criteria, omit equal sign' => [
                 10.5,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree', 'Height'],
@@ -95,7 +95,7 @@ public function providerDAverage(): array
             ],
             'multiple criteria for same field' => [
                 10,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree', 'Height', 'Age', 'Height'],
@@ -108,15 +108,15 @@ public function providerDAverage(): array
                content to return #VALUE! as an invalid name would */
             'field column number too high' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 99,
-                $this->database1(),
+                self::database1(),
             ],
             'field column number too low' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 0,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountATest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountATest.php
index 2fd1172311..0bbd0372af 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountATest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountATest.php
@@ -37,12 +37,12 @@ public function testDCountAAsWorksheetFormula($expectedResult, $database, $field
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDCountA(): array
+    public static function providerDCountA(): array
     {
         return [
             [
                 1,
-                $this->database1(),
+                self::database1(),
                 'Profit',
                 [
                     ['Tree', 'Height', 'Height'],
@@ -51,7 +51,7 @@ public function providerDCountA(): array
             ],
             [
                 2,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -60,7 +60,7 @@ public function providerDCountA(): array
             ],
             [
                 1,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -69,7 +69,7 @@ public function providerDCountA(): array
             ],
             [
                 3,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Score'],
@@ -78,7 +78,7 @@ public function providerDCountA(): array
             ],
             'invalid field name' => [
                 ExcelError::VALUE(),
-                $this->database3(),
+                self::database3(),
                 'Scorex',
                 [
                     ['Subject', 'Score'],
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountTest.php
index 9ed79801c7..a986e70048 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DCountTest.php
@@ -37,7 +37,7 @@ public function testDCountAsWorksheetFormula($expectedResult, $database, $field,
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    private function database4(): array
+    private static function database4(): array
     {
         return [
             ['Status', 'Value'],
@@ -52,12 +52,12 @@ private function database4(): array
         ];
     }
 
-    public function providerDCount(): array
+    public static function providerDCount(): array
     {
         return [
             [
                 1,
-                $this->database1(),
+                self::database1(),
                 'Age',
                 [
                     ['Tree', 'Height', 'Height'],
@@ -66,7 +66,7 @@ public function providerDCount(): array
             ],
             [
                 1,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -75,7 +75,7 @@ public function providerDCount(): array
             ],
             [
                 1,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -84,7 +84,7 @@ public function providerDCount(): array
             ],
             [
                 3,
-                $this->database4(),
+                self::database4(),
                 'Value',
                 [
                     ['Status'],
@@ -93,7 +93,7 @@ public function providerDCount(): array
             ],
             [
                 5,
-                $this->database4(),
+                self::database4(),
                 'Value',
                 [
                     ['Status'],
@@ -102,13 +102,13 @@ public function providerDCount(): array
             ],
             'field column number okay' => [
                 0,
-                $this->database1(),
+                self::database1(),
                 1,
-                $this->database1(),
+                self::database1(),
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database3(),
+                self::database3(),
                 null,
                 [
                     ['Subject', 'Score'],
@@ -121,15 +121,15 @@ public function providerDCount(): array
                content to return #VALUE! as an invalid name would */
             'field column number too high' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 99,
-                $this->database1(),
+                self::database1(),
             ],
             'field column number too low' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 0,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DGetTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DGetTest.php
index 5b0ce9bc6d..24394c7d9a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DGetTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DGetTest.php
@@ -37,12 +37,12 @@ public function testDGetAsWorksheetFormula($expectedResult, $database, $field, $
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDGet(): array
+    public static function providerDGet(): array
     {
         return [
             [
                 ExcelError::NAN(),
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree'],
@@ -52,7 +52,7 @@ public function providerDGet(): array
             ],
             [
                 10,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree', 'Height', 'Height'],
@@ -62,7 +62,7 @@ public function providerDGet(): array
             ],
             [
                 188000,
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Sales Rep.', 'Quarter'],
@@ -71,7 +71,7 @@ public function providerDGet(): array
             ],
             [
                 ExcelError::NAN(),
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Area', 'Quarter'],
@@ -80,9 +80,9 @@ public function providerDGet(): array
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMaxTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMaxTest.php
index d06e4972e1..a4dc9f9e74 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMaxTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMaxTest.php
@@ -37,12 +37,12 @@ public function testDMaxAsWorksheetFormula($expectedResult, $database, $field, $
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDMax(): array
+    public static function providerDMax(): array
     {
         return [
             [
                 96,
-                $this->database1(),
+                self::database1(),
                 'Profit',
                 [
                     ['Tree', 'Height', 'Height'],
@@ -52,7 +52,7 @@ public function providerDMax(): array
             ],
             [
                 340000,
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Quarter', 'Area'],
@@ -61,7 +61,7 @@ public function providerDMax(): array
             ],
             [
                 460000,
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Sales Rep.', 'Quarter'],
@@ -70,15 +70,15 @@ public function providerDMax(): array
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
             'field column number okay' => [
                 18,
-                $this->database1(),
+                self::database1(),
                 2,
-                $this->database1(),
+                self::database1(),
             ],
             /* Excel seems to return #NAME? when column number
                is too high or too low. This makes so little sense
@@ -86,15 +86,15 @@ public function providerDMax(): array
                content to return #VALUE! as an invalid name would */
             'field column number too high' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 99,
-                $this->database1(),
+                self::database1(),
             ],
             'field column number too low' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 0,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMinTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMinTest.php
index d49004eab7..c3257d2722 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMinTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DMinTest.php
@@ -37,12 +37,12 @@ public function testDMinAsWorksheetFormula($expectedResult, $database, $field, $
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDMin(): array
+    public static function providerDMin(): array
     {
         return [
             [
                 75,
-                $this->database1(),
+                self::database1(),
                 'Profit',
                 [
                     ['Tree', 'Height', 'Height'],
@@ -52,7 +52,7 @@ public function providerDMin(): array
             ],
             [
                 0.48,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Age'],
@@ -61,7 +61,7 @@ public function providerDMin(): array
             ],
             [
                 0.55,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -70,15 +70,15 @@ public function providerDMin(): array
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
             'field column number okay' => [
                 8,
-                $this->database1(),
+                self::database1(),
                 2,
-                $this->database1(),
+                self::database1(),
             ],
             /* Excel seems to return #NAME? when column number
                is too high or too low. This makes so little sense
@@ -86,15 +86,15 @@ public function providerDMin(): array
                content to return #VALUE! as an invalid name would */
             'field column number too high' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 99,
-                $this->database1(),
+                self::database1(),
             ],
             'field column number too low' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 0,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DProductTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DProductTest.php
index dc52d73eaa..6aca35b62c 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DProductTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DProductTest.php
@@ -38,7 +38,7 @@ public function testDProductAsWorksheetFormula($expectedResult, $database, $fiel
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    private function database5(): array
+    private static function database5(): array
     {
         return [
             ['Name', 'Date', 'Test', 'Score'],
@@ -57,12 +57,12 @@ private function database5(): array
         ];
     }
 
-    public function providerDProduct(): array
+    public static function providerDProduct(): array
     {
         return [
             [
                 800.0,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree', 'Height', 'Height'],
@@ -72,7 +72,7 @@ public function providerDProduct(): array
             ],
             [
                 36.0,
-                $this->database5(),
+                self::database5(),
                 'Score',
                 [
                     ['Name', 'Date'],
@@ -81,7 +81,7 @@ public function providerDProduct(): array
             ],
             [
                 8.0,
-                $this->database5(),
+                self::database5(),
                 'Score',
                 [
                     ['Test', 'Date'],
@@ -90,9 +90,9 @@ public function providerDProduct(): array
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevPTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevPTest.php
index 9fb869c49e..1c73535732 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevPTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevPTest.php
@@ -37,12 +37,12 @@ public function testDStDevPAsWorksheetFormula($expectedResult, $database, $field
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDStDevP(): array
+    public static function providerDStDevP(): array
     {
         return [
             [
                 2.653299832284,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree'],
@@ -52,7 +52,7 @@ public function providerDStDevP(): array
             ],
             [
                 0.085244745684,
-                $this->database3FilledIn(),
+                self::database3FilledIn(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -61,7 +61,7 @@ public function providerDStDevP(): array
             ],
             [
                 0.160623784042,
-                $this->database3FilledIn(),
+                self::database3FilledIn(),
                 'Score',
                 [
                     ['Subject', 'Age'],
@@ -70,7 +70,7 @@ public function providerDStDevP(): array
             ],
             [
                 0.01,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -79,7 +79,7 @@ public function providerDStDevP(): array
             ],
             [
                 0,
-                $this->database3(),
+                self::database3(),
                 'Score',
                 [
                     ['Subject', 'Age'],
@@ -88,9 +88,9 @@ public function providerDStDevP(): array
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevTest.php
index 55fc5bdfee..7698e73ec4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DStDevTest.php
@@ -37,12 +37,12 @@ public function testDStDevAsWorksheetFormula($expectedResult, $database, $field,
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDStDev(): array
+    public static function providerDStDev(): array
     {
         return [
             [
                 2.966479394838,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree'],
@@ -52,7 +52,7 @@ public function providerDStDev(): array
             ],
             [
                 0.104403065089,
-                $this->database3FilledIn(),
+                self::database3FilledIn(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -61,7 +61,7 @@ public function providerDStDev(): array
             ],
             [
                 0.196723155729,
-                $this->database3FilledIn(),
+                self::database3FilledIn(),
                 'Score',
                 [
                     ['Subject', 'Age'],
@@ -70,9 +70,9 @@ public function providerDStDev(): array
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DSumTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DSumTest.php
index 4525d3edff..6f16c3e658 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DSumTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DSumTest.php
@@ -37,12 +37,12 @@ public function testDSumAsWorksheetFormula($expectedResult, $database, $field, $
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDSum(): array
+    public static function providerDSum(): array
     {
         return [
             [
                 225,
-                $this->database1(),
+                self::database1(),
                 'Profit',
                 [
                     ['Tree'],
@@ -51,7 +51,7 @@ public function providerDSum(): array
             ],
             [
                 247.8,
-                $this->database1(),
+                self::database1(),
                 'Profit',
                 [
                     ['Tree', 'Height', 'Height'],
@@ -61,7 +61,7 @@ public function providerDSum(): array
             ],
             [
                 1210000,
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Quarter', 'Area'],
@@ -70,7 +70,7 @@ public function providerDSum(): array
             ],
             [
                 710000,
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Quarter', 'Sales Rep.'],
@@ -79,7 +79,7 @@ public function providerDSum(): array
             ],
             [
                 705000,
-                $this->database2(),
+                self::database2(),
                 'Sales',
                 [
                     ['Quarter', 'Sales Rep.'],
@@ -88,9 +88,9 @@ public function providerDSum(): array
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarPTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarPTest.php
index 80db8f5638..3e12fd0a6a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarPTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarPTest.php
@@ -37,12 +37,12 @@ public function testDVarPAsWorksheetFormula($expectedResult, $database, $field,
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDVarP(): array
+    public static function providerDVarP(): array
     {
         return [
             [
                 7.04,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree'],
@@ -52,7 +52,7 @@ public function providerDVarP(): array
             ],
             [
                 0.025622222222,
-                $this->database3FilledIn(),
+                self::database3FilledIn(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -61,7 +61,7 @@ public function providerDVarP(): array
             ],
             [
                 0.011622222222,
-                $this->database3FilledIn(),
+                self::database3FilledIn(),
                 'Score',
                 [
                     ['Subject', 'Age'],
@@ -70,9 +70,9 @@ public function providerDVarP(): array
             ],
             'Omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarTest.php
index 46cc6eead1..da8c31c3d8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/DVarTest.php
@@ -37,12 +37,12 @@ public function testDVarAsWorksheetFormula($expectedResult, $database, $field, $
         self::assertEqualsWithDelta($expectedResult, $result, 1.0e-12);
     }
 
-    public function providerDVar(): array
+    public static function providerDVar(): array
     {
         return [
             [
                 8.8,
-                $this->database1(),
+                self::database1(),
                 'Yield',
                 [
                     ['Tree'],
@@ -52,7 +52,7 @@ public function providerDVar(): array
             ],
             [
                 0.038433333333,
-                $this->database3FilledIn(),
+                self::database3FilledIn(),
                 'Score',
                 [
                     ['Subject', 'Gender'],
@@ -61,7 +61,7 @@ public function providerDVar(): array
             ],
             [
                 0.017433333333,
-                $this->database3FilledIn(),
+                self::database3FilledIn(),
                 'Score',
                 [
                     ['Subject', 'Age'],
@@ -70,9 +70,9 @@ public function providerDVar(): array
             ],
             'omitted field name' => [
                 ExcelError::VALUE(),
-                $this->database1(),
+                self::database1(),
                 null,
-                $this->database1(),
+                self::database1(),
             ],
         ];
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/SetupTeardownDatabases.php b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/SetupTeardownDatabases.php
index d442a63357..9c79d9ae13 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/Database/SetupTeardownDatabases.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/Database/SetupTeardownDatabases.php
@@ -37,7 +37,7 @@ protected function tearDown(): void
         Functions::setCompatibilityMode(Functions::COMPATIBILITY_EXCEL);
     }
 
-    protected function database1(): array
+    protected static function database1(): array
     {
         return [
             ['Tree', 'Height', 'Age', 'Yield', 'Profit'],
@@ -50,7 +50,7 @@ protected function database1(): array
         ];
     }
 
-    protected function database2(): array
+    protected static function database2(): array
     {
         return [
             ['Quarter', 'Area', 'Sales Rep.', 'Sales'],
@@ -73,7 +73,7 @@ protected function database2(): array
         ];
     }
 
-    protected function database3(): array
+    protected static function database3(): array
     {
         return [
             ['Name', 'Gender', 'Age', 'Subject', 'Score'],
@@ -92,7 +92,7 @@ protected function database3(): array
         ];
     }
 
-    protected function database3FilledIn(): array
+    protected static function database3FilledIn(): array
     {
         // same as database3 except two omitted scores are filled in
         return [
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortByTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortByTest.php
index 345f732bdf..616ba93678 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortByTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortByTest.php
@@ -30,7 +30,7 @@ public function testSortByWithArgumentErrorReturns($sortIndex, $sortOrder = 1):
         self::assertSame(ExcelError::VALUE(), $result);
     }
 
-    public function providerSortWithScalarArgumentErrorReturns(): array
+    public static function providerSortWithScalarArgumentErrorReturns(): array
     {
         return [
             'Non-array sortIndex' => ['A', 1],
@@ -51,7 +51,7 @@ public function testSortByRow(array $expectedResult, array $matrix, ...$args): v
         self::assertSame($expectedResult, $result);
     }
 
-    public function providerSortByRow(): array
+    public static function providerSortByRow(): array
     {
         return [
             'Simple sort by age' => [
@@ -65,8 +65,8 @@ public function providerSortByRow(): array
                     ['Hector', 66],
                     ['Sal', 73],
                 ],
-                $this->sampleDataForSimpleSort(),
-                array_column($this->sampleDataForSimpleSort(), 1),
+                self::sampleDataForSimpleSort(),
+                array_column(self::sampleDataForSimpleSort(), 1),
             ],
             'Simple sort by name' => [
                 [
@@ -79,8 +79,8 @@ public function providerSortByRow(): array
                     ['Tom', 52],
                     ['Xi', 19],
                 ],
-                $this->sampleDataForSimpleSort(),
-                array_column($this->sampleDataForSimpleSort(), 0),
+                self::sampleDataForSimpleSort(),
+                array_column(self::sampleDataForSimpleSort(), 0),
             ],
             'Row vector' => [
                 [
@@ -93,7 +93,7 @@ public function providerSortByRow(): array
                     ['Tom', 52],
                     ['Xi', 19],
                 ],
-                $this->sampleDataForSimpleSort(),
+                self::sampleDataForSimpleSort(),
                 ['Tom', 'Fred', 'Amy', 'Sal', 'Fritz', 'Srivan', 'Xi', 'Hector'],
             ],
             'Column vector' => [
@@ -107,7 +107,7 @@ public function providerSortByRow(): array
                     ['Tom', 52],
                     ['Xi', 19],
                 ],
-                $this->sampleDataForSimpleSort(),
+                self::sampleDataForSimpleSort(),
                 [['Tom'], ['Fred'], ['Amy'], ['Sal'], ['Fritz'], ['Srivan'], ['Xi'], ['Hector']],
             ],
             'Sort by region asc, name asc' => [
@@ -121,10 +121,10 @@ public function providerSortByRow(): array
                     ['West', 'Fred', 65],
                     ['West', 'Srivan', 39],
                 ],
-                $this->sampleDataForMultiSort(),
-                array_column($this->sampleDataForMultiSort(), 0),
+                self::sampleDataForMultiSort(),
+                array_column(self::sampleDataForMultiSort(), 0),
                 Sort::ORDER_ASCENDING,
-                array_column($this->sampleDataForMultiSort(), 1),
+                array_column(self::sampleDataForMultiSort(), 1),
             ],
             'Sort by region asc, age desc' => [
                 [
@@ -137,16 +137,16 @@ public function providerSortByRow(): array
                     ['West', 'Fred', 65],
                     ['West', 'Srivan', 39],
                 ],
-                $this->sampleDataForMultiSort(),
-                array_column($this->sampleDataForMultiSort(), 0),
+                self::sampleDataForMultiSort(),
+                array_column(self::sampleDataForMultiSort(), 0),
                 Sort::ORDER_ASCENDING,
-                array_column($this->sampleDataForMultiSort(), 2),
+                array_column(self::sampleDataForMultiSort(), 2),
                 Sort::ORDER_DESCENDING,
             ],
         ];
     }
 
-    private function sampleDataForSimpleSort(): array
+    private static function sampleDataForSimpleSort(): array
     {
         return [
             ['Tom', 52],
@@ -160,7 +160,7 @@ private function sampleDataForSimpleSort(): array
         ];
     }
 
-    private function sampleDataForMultiSort(): array
+    private static function sampleDataForMultiSort(): array
     {
         return [
             ['North', 'Amy', 22],
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortTest.php
index bd120e301c..1cd2a138c8 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/LookupRef/SortTest.php
@@ -30,7 +30,7 @@ public function testSortWithScalarArgumentErrorReturns($sortIndex, $sortOrder =
         self::assertSame(ExcelError::VALUE(), $result);
     }
 
-    public function providerSortWithScalarArgumentErrorReturns(): array
+    public static function providerSortWithScalarArgumentErrorReturns(): array
     {
         return [
             'Negative sortIndex' => [-1, -1],
@@ -58,17 +58,17 @@ public function testSortByRow(array $expectedResult, array $matrix, int $sortInd
         self::assertSame($expectedResult, $result);
     }
 
-    public function providerSortByRow(): array
+    public static function providerSortByRow(): array
     {
         return [
             [
                 [[142], [378], [404], [445], [483], [622], [650], [691], [783], [961]],
-                $this->sampleDataForRow(),
+                self::sampleDataForRow(),
                 1,
             ],
             [
                 [[961], [783], [691], [650], [622], [483], [445], [404], [378], [142]],
-                $this->sampleDataForRow(),
+                self::sampleDataForRow(),
                 1,
                 Sort::ORDER_DESCENDING,
             ],
@@ -89,7 +89,7 @@ public function testSortByRowMultiLevel(array $expectedResult, array $matrix, ar
         self::assertSame($expectedResult, $result);
     }
 
-    public function providerSortByRowMultiLevel(): array
+    public static function providerSortByRowMultiLevel(): array
     {
         return [
             [
@@ -107,7 +107,7 @@ public function providerSortByRowMultiLevel(): array
                     ['West', 'Lemons', 34],
                     ['West', 'Oranges', 25],
                 ],
-                $this->sampleDataForMultiRow(),
+                self::sampleDataForMultiRow(),
                 [1, 2],
             ],
             [
@@ -125,7 +125,7 @@ public function providerSortByRowMultiLevel(): array
                     ['West', 'Apples', 30],
                     ['West', 'Lemons', 34],
                 ],
-                $this->sampleDataForMultiRow(),
+                self::sampleDataForMultiRow(),
                 [1, 3],
             ],
             [
@@ -143,7 +143,7 @@ public function providerSortByRowMultiLevel(): array
                     ['North', 'Peaches', 25],
                     ['South', 'Pears', 40],
                 ],
-                $this->sampleDataForMultiRow(),
+                self::sampleDataForMultiRow(),
                 [2, 3],
             ],
         ];
@@ -158,32 +158,32 @@ public function testSortByColumn(array $expectedResult, array $matrix, int $sort
         self::assertSame($expectedResult, $result);
     }
 
-    public function providerSortByColumn(): array
+    public static function providerSortByColumn(): array
     {
         return [
             [
                 [[142, 378, 404, 445, 483, 622, 650, 691, 783, 961]],
-                $this->sampleDataForColumn(),
+                self::sampleDataForColumn(),
                 1,
                 Sort::ORDER_ASCENDING,
             ],
             [
                 [[961, 783, 691, 650, 622, 483, 445, 404, 378, 142]],
-                $this->sampleDataForColumn(),
+                self::sampleDataForColumn(),
                 1,
                 Sort::ORDER_DESCENDING,
             ],
         ];
     }
 
-    public function sampleDataForRow(): array
+    public static function sampleDataForRow(): array
     {
         return [
             [622], [961], [691], [445], [378], [483], [650], [783], [142], [404],
         ];
     }
 
-    public function sampleDataForMultiRow(): array
+    public static function sampleDataForMultiRow(): array
     {
         return [
             ['South', 'Pears', 40],
@@ -201,7 +201,7 @@ public function sampleDataForMultiRow(): array
         ];
     }
 
-    public function sampleDataForColumn(): array
+    public static function sampleDataForColumn(): array
     {
         return [
             [622, 961, 691, 445, 378, 483, 650, 783, 142, 404],
diff --git a/tests/PhpSpreadsheetTests/Cell/CellTest.php b/tests/PhpSpreadsheetTests/Cell/CellTest.php
index 2ed095bfe1..2008153744 100644
--- a/tests/PhpSpreadsheetTests/Cell/CellTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/CellTest.php
@@ -301,7 +301,7 @@ public function testAppliedStyleSingleCell(string $cellAddress, string $fillStyl
         }
     }
 
-    public function appliedStyling(): array
+    public static function appliedStyling(): array
     {
         return [
             'A1 - Conditional with Match' => ['A1', Fill::FILL_SOLID, Color::COLOR_RED],
diff --git a/tests/PhpSpreadsheetTests/Custom/ComplexAssert.php b/tests/PhpSpreadsheetTests/Custom/ComplexAssert.php
index 0b3f18f4c4..0341041279 100644
--- a/tests/PhpSpreadsheetTests/Custom/ComplexAssert.php
+++ b/tests/PhpSpreadsheetTests/Custom/ComplexAssert.php
@@ -15,6 +15,11 @@ class ComplexAssert extends TestCase
     /** @var float */
     private $delta = 0.0;
 
+    public function __construct()
+    {
+        parent::__construct('complexAssert');
+    }
+
     /**
      * @param mixed $expected
      * @param mixed $actual
diff --git a/tests/PhpSpreadsheetTests/Helper/SampleTest.php b/tests/PhpSpreadsheetTests/Helper/SampleTest.php
index 384011e83d..387597f7d1 100644
--- a/tests/PhpSpreadsheetTests/Helper/SampleTest.php
+++ b/tests/PhpSpreadsheetTests/Helper/SampleTest.php
@@ -16,16 +16,14 @@ class SampleTest extends TestCase
      */
     public function testSample(string $sample): void
     {
-        // Suppress output to console
-        $this->setOutputCallback(function (): void {
-        });
-
+        ob_start();
         require $sample;
+        ob_end_clean();
 
         self::assertTrue(true);
     }
 
-    public function providerSample(): array
+    public static function providerSample(): array
     {
         $skipped = [
         ];
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlLibxmlTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlLibxmlTest.php
new file mode 100644
index 0000000000..d5f5044aa0
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlLibxmlTest.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
+
+use PhpOffice\PhpSpreadsheet\Reader\Html;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Dom loadHtml usually succeeds even with invalid Html,
+ * although it will generate warning messages.
+ * This member demonstrates a method less intrusive than
+ * set_error_handler to detect if there has been a problem.
+ * I want it run in a separate
+ * process because I am nervous about libxml_use_internal_errors.
+ *
+ * @runTestsInSeparateProcesses
+ */
+class HtmlLibxmlTest extends TestCase
+{
+    /** @var bool */
+    private $useErrors;
+
+    protected function setUp(): void
+    {
+        $this->useErrors = libxml_use_internal_errors(true);
+    }
+
+    protected function tearDown(): void
+    {
+        libxml_use_internal_errors($this->useErrors);
+    }
+
+    public function testLoadInvalidString(): void
+    {
+        $html = '<table<>';
+        (new Html())->loadFromString($html);
+        self::assertNotEmpty(libxml_get_errors());
+    }
+
+    public function testLoadValidString(): void
+    {
+        $html = '<table>';
+        (new Html())->loadFromString($html);
+        self::assertEmpty(libxml_get_errors());
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlLoadStringTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlLoadStringTest.php
index 91869dc6a0..5fa7ccf43f 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlLoadStringTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlLoadStringTest.php
@@ -40,12 +40,14 @@ public function testCanLoadFromString(): void
 
     public function testLoadInvalidString(): void
     {
-        $this->expectException(ReaderException::class);
-        $html = '<table<>';
-        $spreadsheet = (new Html())->loadFromString($html);
-        $firstSheet = $spreadsheet->getSheet(0);
-        $cellStyle = $firstSheet->getStyle('A1');
-        self::assertFalse($cellStyle->getAlignment()->getWrapText());
+        if (method_exists($this, 'setOutputCallback')) {
+            $this->expectException(ReaderException::class);
+            $html = '<table<>';
+            (new Html())->loadFromString($html);
+        } else {
+            // The meat of this test runs in HtmlPhpunit10Test
+            self::assertTrue(true);
+        }
     }
 
     public function testCanLoadFromStringIntoExistingSpreadsheet(): void
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlPhpunit10Test.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlPhpunit10Test.php
new file mode 100644
index 0000000000..fce30b121a
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlPhpunit10Test.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Html;
+
+use PhpOffice\PhpSpreadsheet\Reader\Html;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * There were problems running this test in HtmlTest with PhpUnit 10.
+ * This replacement seem to work. I want it run in a separate
+ * process because I am nervous about set_error_handler.
+ *
+ * @runTestsInSeparateProcesses
+ */
+class HtmlPhpunit10Test extends TestCase
+{
+    /** @var string */
+    private static $errorString;
+
+    protected function setUp(): void
+    {
+        self::$errorString = '';
+        set_error_handler([self::class, 'errorHandler']);
+    }
+
+    protected function tearDown(): void
+    {
+        restore_error_handler();
+    }
+
+    public static function errorHandler(int $errno, string $errstr): bool
+    {
+        if ($errno === E_WARNING) {
+            self::$errorString = $errstr;
+
+            return true; // stop error handling
+        }
+
+        return false; // continue error handling
+    }
+
+    public function testBadHtml(): void
+    {
+        $filename = 'tests/data/Reader/HTML/badhtml.html';
+        $reader = new Html();
+        self::assertTrue($reader->canRead($filename));
+        $reader->load($filename);
+        self::assertStringContainsString('DOMDocument::loadHTML', self::$errorString);
+    }
+
+    public function testLoadInvalidString(): void
+    {
+        $html = '<table<>';
+        (new Html())->loadFromString($html);
+        self::assertStringContainsString('DOMDocument::loadHTML', self::$errorString);
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Reader/Html/HtmlTest.php b/tests/PhpSpreadsheetTests/Reader/Html/HtmlTest.php
index 38379b8ab1..5f80b2581b 100644
--- a/tests/PhpSpreadsheetTests/Reader/Html/HtmlTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Html/HtmlTest.php
@@ -25,8 +25,12 @@ public function testBadHtml(): void
         $reader = new Html();
         self::assertTrue($reader->canRead($filename));
 
-        $this->expectException(ReaderException::class);
-        $reader->load($filename);
+        if (method_exists($this, 'setOutputCallback')) {
+            // The meat of this test is moved to HtmlPhpunit10Test
+            // to run under all PhpUnit versions.
+            $this->expectException(ReaderException::class);
+            $reader->load($filename);
+        }
     }
 
     public function testNonHtml(): void
@@ -46,7 +50,7 @@ public function testInvalidFilename(): void
         self::assertFalse($reader->canRead(''));
     }
 
-    public function providerCanReadVerySmallFile(): array
+    public static function providerCanReadVerySmallFile(): array
     {
         $padding = str_repeat('a', 2048);
 
diff --git a/tests/PhpSpreadsheetTests/Reader/Xml/XmlTest.php b/tests/PhpSpreadsheetTests/Reader/Xml/XmlTest.php
index def2d63ec8..e2e1a9ce0c 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xml/XmlTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xml/XmlTest.php
@@ -13,13 +13,16 @@ class XmlTest extends TestCase
      */
     public function testInvalidSimpleXML(string $filename): void
     {
-        $this->expectException(\PhpOffice\PhpSpreadsheet\Reader\Exception::class);
-
         $xmlReader = new Xml();
-        $xmlReader->trySimpleXMLLoadString($filename);
+        if (method_exists($this, 'setOutputCallback')) {
+            $this->expectException(\PhpOffice\PhpSpreadsheet\Reader\Exception::class);
+            self::assertFalse($xmlReader->trySimpleXMLLoadString($filename));
+        }
+
+        self::assertFalse(@$xmlReader->trySimpleXMLLoadString($filename));
     }
 
-    public function providerInvalidSimpleXML(): array
+    public static function providerInvalidSimpleXML(): array
     {
         $tests = [];
         $glob = glob('tests/data/Reader/Xml/XEETestInvalidSimpleXML*.xml');
@@ -54,7 +57,8 @@ public function testLoadCorruptedFile(): void
         $this->expectException(\PhpOffice\PhpSpreadsheet\Reader\Exception::class);
 
         $xmlReader = new Xml();
-        $xmlReader->load('tests/data/Reader/Xml/CorruptedXmlFile.xml');
+        $spreadsheet = /** @scrutinizer ignore-unhandled */ @$xmlReader->load('tests/data/Reader/Xml/CorruptedXmlFile.xml');
+        self::assertNotSame('', $spreadsheet->getID());
     }
 
     public function testListWorksheetNamesCorruptedFile(): void
@@ -62,7 +66,8 @@ public function testListWorksheetNamesCorruptedFile(): void
         $this->expectException(\PhpOffice\PhpSpreadsheet\Reader\Exception::class);
 
         $xmlReader = new Xml();
-        $xmlReader->listWorksheetNames('tests/data/Reader/Xml/CorruptedXmlFile.xml');
+        $names = /** @scrutinizer ignore-unhandled */ @$xmlReader->listWorksheetNames('tests/data/Reader/Xml/CorruptedXmlFile.xml');
+        self::assertNotEmpty($names);
     }
 
     public function testListWorksheetInfoCorruptedFile(): void
@@ -70,6 +75,7 @@ public function testListWorksheetInfoCorruptedFile(): void
         $this->expectException(\PhpOffice\PhpSpreadsheet\Reader\Exception::class);
 
         $xmlReader = new Xml();
-        $xmlReader->listWorksheetInfo('tests/data/Reader/Xml/CorruptedXmlFile.xml');
+        $info = /** @scrutinizer ignore-unhandled */ @$xmlReader->listWorksheetInfo('tests/data/Reader/Xml/CorruptedXmlFile.xml');
+        self::assertNotEmpty($info);
     }
 }
diff --git a/tests/PhpSpreadsheetTests/Shared/OLEPhpunit10Test.php b/tests/PhpSpreadsheetTests/Shared/OLEPhpunit10Test.php
new file mode 100644
index 0000000000..2bf88b3ff3
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Shared/OLEPhpunit10Test.php
@@ -0,0 +1,63 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Shared;
+
+use PhpOffice\PhpSpreadsheet\Shared\OLE;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * There were problems running these tests in OLETest with PhpUnit 10.
+ * These replacements seem to work. I want them run in separate
+ * processes because I am nervous about set_error_handler.
+ *
+ * @runTestsInSeparateProcesses
+ */
+class OLEPhpunit10Test extends TestCase
+{
+    /** @var string */
+    private static $errorString;
+
+    protected function setUp(): void
+    {
+        self::$errorString = '';
+        set_error_handler([self::class, 'errorHandler']);
+    }
+
+    protected function tearDown(): void
+    {
+        restore_error_handler();
+    }
+
+    public static function errorHandler(int $errno, string $errstr): bool
+    {
+        if ($errno === E_USER_WARNING) {
+            self::$errorString = $errstr;
+
+            return true; // stop error handling
+        }
+
+        return false; // continue error handling
+    }
+
+    public function testChainedWriteMode(): void
+    {
+        self::assertSame('', self::$errorString);
+        $ole = new OLE\ChainedBlockStream();
+        $openedPath = '';
+        self::assertFalse($ole->stream_open('whatever', 'w', 0, $openedPath));
+
+        $ole->stream_open('whatever', 'w', STREAM_REPORT_ERRORS, $openedPath);
+        self::assertSame('Only reading is supported', self::$errorString);
+    }
+
+    public function testChainedBadPath(): void
+    {
+        self::assertSame('', self::$errorString);
+        $ole = new OLE\ChainedBlockStream();
+        $openedPath = '';
+        self::assertFalse($ole->stream_open('whatever', 'r', 0, $openedPath));
+
+        $ole->stream_open('whatever', 'r', STREAM_REPORT_ERRORS, $openedPath);
+        self::assertSame('OLE stream not found', self::$errorString);
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Shared/OLETest.php b/tests/PhpSpreadsheetTests/Shared/OLETest.php
index bef137f27c..db81272c55 100644
--- a/tests/PhpSpreadsheetTests/Shared/OLETest.php
+++ b/tests/PhpSpreadsheetTests/Shared/OLETest.php
@@ -46,11 +46,14 @@ public function testChainedWriteMode(): void
         $openedPath = '';
         self::assertFalse($ole->stream_open('whatever', 'w', 0, $openedPath));
 
-        try {
-            $ole->stream_open('whatever', 'w', STREAM_REPORT_ERRORS, $openedPath);
-            self::fail('Error in statement above should be caught');
-        } catch (Throwable $e) {
-            self::assertSame('Only reading is supported', $e->getMessage());
+        // Test moved to OLEPhpunit10Test for PhpUnit 10
+        if (method_exists($this, 'setOutputCallback')) {
+            try {
+                $ole->stream_open('whatever', 'w', STREAM_REPORT_ERRORS, $openedPath);
+                self::fail('Error in statement above should be caught');
+            } catch (Throwable $e) {
+                self::assertSame('Only reading is supported', $e->getMessage());
+            }
         }
     }
 
@@ -60,11 +63,14 @@ public function testChainedBadPath(): void
         $openedPath = '';
         self::assertFalse($ole->stream_open('whatever', 'r', 0, $openedPath));
 
-        try {
-            $ole->stream_open('whatever', 'r', STREAM_REPORT_ERRORS, $openedPath);
-            self::fail('Error in statement above should be caught');
-        } catch (Throwable $e) {
-            self::assertSame('OLE stream not found', $e->getMessage());
+        // Not sure how to do this test with PhpUnit 10
+        if (method_exists($this, 'setOutputCallback')) {
+            try {
+                $ole->stream_open('whatever', 'r', STREAM_REPORT_ERRORS, $openedPath);
+                self::fail('Error in statement above should be caught');
+            } catch (Throwable $e) {
+                self::assertSame('OLE stream not found', $e->getMessage());
+            }
         }
     }
 }
diff --git a/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorEmptyTest.php b/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorEmptyTest.php
index 70cc39ec13..47c403729b 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorEmptyTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/ColumnIteratorEmptyTest.php
@@ -45,7 +45,7 @@ public function testIteratorEmptyColumn(string $columnId, bool $expectedEmpty):
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function emptyColumnBasic(): array
+    public static function emptyColumnBasic(): array
     {
         return [
             ['A', false],
@@ -75,7 +75,7 @@ public function testIteratorEmptyColumnWithNull(string $columnId, bool $expected
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function emptyColumnNullAsEmpty(): array
+    public static function emptyColumnNullAsEmpty(): array
     {
         return [
             ['A', false],
@@ -105,7 +105,7 @@ public function testIteratorEmptyColumnWithEmptyString(string $columnId, bool $e
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function emptyColumnEmptyStringAsEmpty(): array
+    public static function emptyColumnEmptyStringAsEmpty(): array
     {
         return [
             ['A', false],
@@ -137,7 +137,7 @@ public function testIteratorEmptyColumnWithNullAndEmptyString(string $columnId,
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function emptyColumnNullAndEmptyStringAsEmpty(): array
+    public static function emptyColumnNullAndEmptyStringAsEmpty(): array
     {
         return [
             ['A', false],
diff --git a/tests/PhpSpreadsheetTests/Worksheet/MergeBehaviourTest.php b/tests/PhpSpreadsheetTests/Worksheet/MergeBehaviourTest.php
index 7d7a2c8366..ab79ad8302 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/MergeBehaviourTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/MergeBehaviourTest.php
@@ -11,7 +11,7 @@ class MergeBehaviourTest extends AbstractFunctional
     /**
      * @var array
      */
-    private $testDataRaw = [
+    private static $testDataRaw = [
         [1.1, 2.2, '=ROUND(A1+B1, 1)'],
         [4.4, 5.5, '=ROUND(A2+B2, 1)'],
         ['=ROUND(A1+A2, 1)', '=ROUND(B1+B2, 1)', '=ROUND(A3+B3, 1)'],
@@ -35,7 +35,7 @@ public function testMergeCellsDefaultBehaviour(): void
         $mergeRange = 'A1:C3';
         $spreadsheet = new Spreadsheet();
         $worksheet = $spreadsheet->getActiveSheet();
-        $worksheet->fromArray($this->testDataRaw, null, 'A1', true);
+        $worksheet->fromArray(self::$testDataRaw, null, 'A1', true);
         $worksheet->mergeCells($mergeRange);
 
         $mergeResult = $worksheet->toArray(null, true, false, false);
@@ -72,7 +72,7 @@ public function testMergeCellsHideBehaviour(): void
         $mergeRange = 'A1:C3';
         $spreadsheet = new Spreadsheet();
         $worksheet = $spreadsheet->getActiveSheet();
-        $worksheet->fromArray($this->testDataRaw, null, 'A1', true);
+        $worksheet->fromArray(self::$testDataRaw, null, 'A1', true);
         $worksheet->mergeCells($mergeRange, Worksheet::MERGE_CELL_CONTENT_HIDE);
 
         $mergeResult = $worksheet->toArray(null, true, false, false);
@@ -115,11 +115,11 @@ public function testMergeCellsMergeBehaviour(array $testData, string $mergeRange
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function mergeCellsMergeBehaviourProvider(): array
+    public static function mergeCellsMergeBehaviourProvider(): array
     {
         return [
             'With Calculated Values' => [
-                $this->testDataRaw,
+                self::$testDataRaw,
                 'A1:C3',
                 [
                     ['1.1 2.2 1.1 4.4 5.5 0 1.1 0 0', null, null],
diff --git a/tests/PhpSpreadsheetTests/Worksheet/RowIteratorEmptyTest.php b/tests/PhpSpreadsheetTests/Worksheet/RowIteratorEmptyTest.php
index c971f6dfe8..ec062a032f 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/RowIteratorEmptyTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/RowIteratorEmptyTest.php
@@ -47,7 +47,7 @@ public function testIteratorEmptyRow(int $rowId, bool $expectedEmpty): void
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function emptyRowBasic(): array
+    public static function emptyRowBasic(): array
     {
         return [
             [1, false],
@@ -77,7 +77,7 @@ public function testIteratorEmptyRowWithNull(int $rowId, bool $expectedEmpty): v
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function emptyRowNullAsEmpty(): array
+    public static function emptyRowNullAsEmpty(): array
     {
         return [
             [1, false],
@@ -107,7 +107,7 @@ public function testIteratorEmptyRowWithEmptyString(int $rowId, bool $expectedEm
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function emptyRowEmptyStringAsEmpty(): array
+    public static function emptyRowEmptyStringAsEmpty(): array
     {
         return [
             [1, false],
@@ -139,7 +139,7 @@ public function testIteratorEmptyRowWithNullAndEmptyString(int $rowId, bool $exp
         $spreadsheet->disconnectWorksheets();
     }
 
-    public function emptyRowNullAndEmptyStringAsEmpty(): array
+    public static function emptyRowNullAndEmptyStringAsEmpty(): array
     {
         return [
             [1, false],
diff --git a/tests/PhpSpreadsheetTests/Worksheet/Table/TableTest.php b/tests/PhpSpreadsheetTests/Worksheet/Table/TableTest.php
index 26e537ba42..8c7a4e8eae 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/Table/TableTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/Table/TableTest.php
@@ -36,7 +36,7 @@ public function testValidTableNames(string $name, string $expected): void
         self::assertEquals($expected, $table->getName());
     }
 
-    public function validTableNamesProvider(): array
+    public static function validTableNamesProvider(): array
     {
         return [
             ['', ''],
@@ -61,7 +61,7 @@ public function testInvalidTableNames(string $name): void
         $table->setName($name);
     }
 
-    public function invalidTableNamesProvider(): array
+    public static function invalidTableNamesProvider(): array
     {
         return [
             ['C'],
@@ -152,12 +152,10 @@ public function testGetRange(): void
     }
 
     /**
-     * @dataProvider validTableRangeProvider
-     *
      * @param AddressRange|array<int>|string $fullRange
      * @param string $fullRange
      */
-    public function testSetRangeValidRange($fullRange, string $actualRange): void
+    public function xtestSetRangeValidRange($fullRange, string $actualRange): void
     {
         $table = new Table(self::INITIAL_RANGE);
 
@@ -166,7 +164,14 @@ public function testSetRangeValidRange($fullRange, string $actualRange): void
         self::assertEquals($actualRange, $table->getRange());
     }
 
-    public function validTableRangeProvider(): array
+    public function testSetRangeValidRange(): void
+    {
+        foreach ($this->validTableRanges() as $arrayEntry) {
+            $this->xtestSetRangeValidRange($arrayEntry[0], $arrayEntry[1]);
+        }
+    }
+
+    public function validTableRanges(): array
     {
         $sheet = $this->getSheet();
         $title = $sheet->getTitle();
@@ -203,7 +208,7 @@ public function testSetRangeInvalidRange(string $range): void
         new Table($range);
     }
 
-    public function invalidTableRangeProvider(): array
+    public static function invalidTableRangeProvider(): array
     {
         return [
             ['A1'],
diff --git a/tests/PhpSpreadsheetTests/Writer/Xls/WorkbookTest.php b/tests/PhpSpreadsheetTests/Writer/Xls/WorkbookTest.php
index 160a665ad3..ed3deb3e6a 100644
--- a/tests/PhpSpreadsheetTests/Writer/Xls/WorkbookTest.php
+++ b/tests/PhpSpreadsheetTests/Writer/Xls/WorkbookTest.php
@@ -15,9 +15,23 @@ class WorkbookTest extends TestCase
      */
     private $workbook;
 
-    protected function setUp(): void
+    /** @var ?Spreadsheet */
+    private $spreadsheet;
+
+    protected function tearDown(): void
+    {
+        if ($this->spreadsheet !== null) {
+            $this->spreadsheet->disconnectWorksheets();
+            $this->spreadsheet = null;
+        }
+    }
+
+    private function setUpWorkbook(): void
     {
-        $spreadsheet = new Spreadsheet();
+        if ($this->spreadsheet !== null) {
+            $this->spreadsheet->disconnectWorksheets();
+        }
+        $this->spreadsheet = $spreadsheet = new Spreadsheet();
         $strTotal = 0;
         $strUnique = 0;
         $str_table = [];
@@ -27,10 +41,7 @@ protected function setUp(): void
         $this->workbook = new Workbook($spreadsheet, $strTotal, $strUnique, $str_table, $colors, $parser);
     }
 
-    /**
-     * @dataProvider providerAddColor
-     */
-    public function testAddColor(array $testColors, array $expectedResult): void
+    public function xtestAddColor(array $testColors, array $expectedResult): void
     {
         $workbookReflection = new ReflectionClass(Workbook::class);
         $methodAddColor = $workbookReflection->getMethod('addColor');
@@ -47,9 +58,20 @@ public function testAddColor(array $testColors, array $expectedResult): void
         self::assertEquals($expectedResult, $palette);
     }
 
-    public function providerAddColor(): array
+    public function testAddColor(): void
+    {
+        $i = 0;
+        $arrayEntries = $this->arrayAddColor();
+        while ($i < count($arrayEntries)) {
+            $this->xtestAddColor($arrayEntries[$i][0], $arrayEntries[$i][1]);
+            ++$i;
+            $arrayEntries = $this->arrayAddColor();
+        }
+    }
+
+    public function arrayAddColor(): array
     {
-        $this->setUp();
+        $this->setUpWorkbook();
 
         $workbookReflection = new ReflectionClass(Workbook::class);
         $propertyPalette = $workbookReflection->getProperty('palette');