diff --git a/tests/PhpSpreadsheetTests/Calculation/CalculationTest.php b/tests/PhpSpreadsheetTests/Calculation/CalculationTest.php
index 86ca7a3e..4b81fbf4 100644
--- a/tests/PhpSpreadsheetTests/Calculation/CalculationTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/CalculationTest.php
@@ -52,7 +52,7 @@ class CalculationTest extends TestCase
      */
     public function testGetFunctions($category, $functionCall, $argumentCount)
     {
-        self::assertInternalType('callable', $functionCall);
+        self::assertIsCallable($functionCall);
     }
 
     public function providerGetFunctions()
diff --git a/tests/PhpSpreadsheetTests/Calculation/EngineeringTest.php b/tests/PhpSpreadsheetTests/Calculation/EngineeringTest.php
index 1ea22443..003ef206 100644
--- a/tests/PhpSpreadsheetTests/Calculation/EngineeringTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/EngineeringTest.php
@@ -970,25 +970,25 @@ class EngineeringTest extends TestCase
     public function testGetConversionGroups()
     {
         $result = Engineering::getConversionGroups();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
     }
 
     public function testGetConversionGroupUnits()
     {
         $result = Engineering::getConversionGroupUnits();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
     }
 
     public function testGetConversionGroupUnitDetails()
     {
         $result = Engineering::getConversionGroupUnitDetails();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
     }
 
     public function testGetConversionMultipliers()
     {
         $result = Engineering::getConversionMultipliers();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
     }
 
     /**
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php
index 08587336..6628322a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateTest.php
@@ -49,7 +49,7 @@ class DateTest extends TestCase
 
         $result = DateTime::DATE(2012, 1, 31);
         //    Must return an object...
-        $this->assertInternalType('object', $result);
+        self::assertIsObject($result);
         //    ... of the correct type
         $this->assertTrue(is_a($result, 'DateTimeInterface'));
         //    ... with the correct value
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php
index 937fc10a..2c4e96eb 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/DateValueTest.php
@@ -2,6 +2,7 @@
 
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\DateTime;
 
+use DateTimeInterface;
 use PhpOffice\PhpSpreadsheet\Calculation\DateTime;
 use PhpOffice\PhpSpreadsheet\Calculation\Functions;
 use PhpOffice\PhpSpreadsheet\Shared\Date;
@@ -47,9 +48,9 @@ class DateValueTest extends TestCase
 
         $result = DateTime::DATEVALUE('2012-1-31');
         //    Must return an object...
-        $this->assertInternalType('object', $result);
+        self::assertIsObject($result);
         //    ... of the correct type
-        $this->assertTrue(is_a($result, 'DateTimeInterface'));
+        $this->assertTrue(is_a($result, DateTimeInterface::class));
         //    ... with the correct value
         $this->assertEquals($result->format('d-M-Y'), '31-Jan-2012');
     }
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EDateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EDateTest.php
index 74c4a388..7f885096 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EDateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EDateTest.php
@@ -48,7 +48,7 @@ class EDateTest extends TestCase
 
         $result = DateTime::EDATE('2012-1-26', -1);
         //    Must return an object...
-        $this->assertInternalType('object', $result);
+        self::assertIsObject($result);
         //    ... of the correct type
         $this->assertTrue(is_a($result, 'DateTimeInterface'));
         //    ... with the correct value
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EoMonthTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EoMonthTest.php
index edb9d7ed..6092151a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EoMonthTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/EoMonthTest.php
@@ -48,7 +48,7 @@ class EoMonthTest extends TestCase
 
         $result = DateTime::EOMONTH('2012-1-26', -1);
         //    Must return an object...
-        $this->assertInternalType('object', $result);
+        self::assertIsObject($result);
         //    ... of the correct type
         $this->assertTrue(is_a($result, 'DateTimeInterface'));
         //    ... with the correct value
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php
index 5a0f3b00..61406f5a 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeTest.php
@@ -46,7 +46,7 @@ class TimeTest extends TestCase
 
         $result = DateTime::TIME(7, 30, 20);
         //    Must return an object...
-        $this->assertInternalType('object', $result);
+        self::assertIsObject($result);
         //    ... of the correct type
         $this->assertTrue(is_a($result, 'DateTimeInterface'));
         //    ... with the correct value
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeValueTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeValueTest.php
index 6a45f6a3..4fc09a2d 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeValueTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/DateTime/TimeValueTest.php
@@ -46,7 +46,7 @@ class TimeValueTest extends TestCase
 
         $result = DateTime::TIMEVALUE('7:30:20');
         //    Must return an object...
-        $this->assertInternalType('object', $result);
+        self::assertIsObject($result);
         //    ... of the correct type
         $this->assertTrue(is_a($result, 'DateTimeInterface'));
         //    ... with the correct value
diff --git a/tests/PhpSpreadsheetTests/Cell/DataTypeTest.php b/tests/PhpSpreadsheetTests/Cell/DataTypeTest.php
index c450e6e1..1e1b5ecc 100644
--- a/tests/PhpSpreadsheetTests/Cell/DataTypeTest.php
+++ b/tests/PhpSpreadsheetTests/Cell/DataTypeTest.php
@@ -10,7 +10,7 @@ class DataTypeTest extends TestCase
     public function testGetErrorCodes()
     {
         $result = DataType::getErrorCodes();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
         self::assertGreaterThan(0, count($result));
         self::assertArrayHasKey('#NULL!', $result);
     }
diff --git a/tests/PhpSpreadsheetTests/Reader/OdsTest.php b/tests/PhpSpreadsheetTests/Reader/OdsTest.php
index 59ae006b..bec85f7b 100644
--- a/tests/PhpSpreadsheetTests/Reader/OdsTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/OdsTest.php
@@ -240,28 +240,28 @@ class OdsTest extends TestCase
 
         $properties = $spreadsheet->getProperties();
         // Core Properties
-//        $this->assertSame('Mark Baker', $properties->getCreator());
-        $this->assertSame('Property Test File', $properties->getTitle());
-        $this->assertSame('Testing for Properties', $properties->getSubject());
-        $this->assertSame('TEST ODS PHPSpreadsheet', $properties->getKeywords());
+//        self::assertSame('Mark Baker', $properties->getCreator());
+        self::assertSame('Property Test File', $properties->getTitle());
+        self::assertSame('Testing for Properties', $properties->getSubject());
+        self::assertSame('TEST ODS PHPSpreadsheet', $properties->getKeywords());
 
         // Extended Properties
-//        $this->assertSame('PHPOffice', $properties->getCompany());
-//        $this->assertSame('The Big Boss', $properties->getManager());
+//        self::assertSame('PHPOffice', $properties->getCompany());
+//        self::assertSame('The Big Boss', $properties->getManager());
 
         // Custom Properties
         $customProperties = $properties->getCustomProperties();
-        $this->assertInternalType('array', $customProperties);
+        self::assertIsArray($customProperties);
         $customProperties = array_flip($customProperties);
-        $this->assertArrayHasKey('TestDate', $customProperties);
+        self::assertArrayHasKey('TestDate', $customProperties);
 
         foreach ($customPropertySet as $propertyName => $testData) {
-            $this->assertTrue($properties->isCustomPropertySet($propertyName));
-            $this->assertSame($testData['type'], $properties->getCustomPropertyType($propertyName));
+            self::assertTrue($properties->isCustomPropertySet($propertyName));
+            self::assertSame($testData['type'], $properties->getCustomPropertyType($propertyName));
             if ($properties->getCustomPropertyType($propertyName) == Properties::PROPERTY_TYPE_DATE) {
-                $this->assertSame($testData['value'], date('Y-m-d', $properties->getCustomPropertyValue($propertyName)));
+                self::assertSame($testData['value'], date('Y-m-d', $properties->getCustomPropertyValue($propertyName)));
             } else {
-                $this->assertSame($testData['value'], $properties->getCustomPropertyValue($propertyName));
+                self::assertSame($testData['value'], $properties->getCustomPropertyValue($propertyName));
             }
         }
     }
diff --git a/tests/PhpSpreadsheetTests/Reader/Security/XmlScannerTest.php b/tests/PhpSpreadsheetTests/Reader/Security/XmlScannerTest.php
index c1d7fa38..0d9fc13f 100644
--- a/tests/PhpSpreadsheetTests/Reader/Security/XmlScannerTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Security/XmlScannerTest.php
@@ -82,7 +82,7 @@ class XmlScannerTest extends TestCase
         $scanner = $fileReader->getSecurityScanner();
 
         //    Must return an object...
-        $this->assertInternalType('object', $scanner);
+        self::assertIsObject($scanner);
         //    ... of the correct type
         $this->assertInstanceOf(XmlScanner::class, $scanner);
     }
diff --git a/tests/PhpSpreadsheetTests/Reader/XlsxTest.php b/tests/PhpSpreadsheetTests/Reader/XlsxTest.php
index 5cf6f93f..1180aacc 100644
--- a/tests/PhpSpreadsheetTests/Reader/XlsxTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/XlsxTest.php
@@ -40,7 +40,7 @@ class XlsxTest extends TestCase
 
         // Custom Properties
         $customProperties = $properties->getCustomProperties();
-        $this->assertInternalType('array', $customProperties);
+        self::assertIsArray($customProperties);
         $customProperties = array_flip($customProperties);
         $this->assertArrayHasKey('Publisher', $customProperties);
 
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/ColumnTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/ColumnTest.php
index 9ce636d8..855de2bc 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/ColumnTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilter/ColumnTest.php
@@ -127,7 +127,7 @@ class ColumnTest extends TestCase
         $this->testAutoFilterColumnObject->setAttributes($attributeSet);
 
         $result = $this->testAutoFilterColumnObject->getAttributes();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
         self::assertCount(count($attributeSet), $result);
     }
 
diff --git a/tests/PhpSpreadsheetTests/Worksheet/AutoFilterTest.php b/tests/PhpSpreadsheetTests/Worksheet/AutoFilterTest.php
index 6766aac8..aa66eb8e 100644
--- a/tests/PhpSpreadsheetTests/Worksheet/AutoFilterTest.php
+++ b/tests/PhpSpreadsheetTests/Worksheet/AutoFilterTest.php
@@ -111,7 +111,7 @@ class AutoFilterTest extends TestCase
     {
         //  There should be no columns yet defined
         $result = $this->testAutoFilterObject->getColumns();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
         self::assertCount(0, $result);
     }
 
@@ -151,7 +151,7 @@ class AutoFilterTest extends TestCase
         $result = $this->testAutoFilterObject->getColumns();
         //  Result should be an array of \PhpOffice\PhpSpreadsheet\Worksheet\Worksheet\AutoFilter\Column
         //    objects for each column we set indexed by the column ID
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
         self::assertCount(1, $result);
         self::assertArrayHasKey($expectedResult, $result);
         self::assertInstanceOf(Column::class, $result[$expectedResult]);
@@ -178,7 +178,7 @@ class AutoFilterTest extends TestCase
         $result = $this->testAutoFilterObject->getColumns();
         //  Result should be an array of \PhpOffice\PhpSpreadsheet\Worksheet\Worksheet\AutoFilter\Column
         //    objects for each column we set indexed by the column ID
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
         self::assertCount(1, $result);
         self::assertArrayHasKey($expectedResult, $result);
         self::assertInstanceOf(Column::class, $result[$expectedResult]);
@@ -211,7 +211,7 @@ class AutoFilterTest extends TestCase
         $result = $this->testAutoFilterObject->getColumns();
         //  Result should be an array of \PhpOffice\PhpSpreadsheet\Worksheet\Worksheet\AutoFilter\Column
         //    objects for each column we set indexed by the column ID
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
         self::assertCount(count($columnIndexes), $result);
         foreach ($columnIndexes as $columnIndex) {
             self::assertArrayHasKey($columnIndex, $result);
@@ -288,7 +288,7 @@ class AutoFilterTest extends TestCase
 
         //  Column array should be cleared
         $result = $this->testAutoFilterObject->getColumns();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
         self::assertCount(0, $result);
     }
 
@@ -318,7 +318,7 @@ class AutoFilterTest extends TestCase
         //  Only columns that existed in the original range and that
         //    still fall within the new range should be retained
         $result = $this->testAutoFilterObject->getColumns();
-        self::assertInternalType('array', $result);
+        self::assertIsArray($result);
         self::assertCount(count($columnIndexes1), $result);
     }