diff --git a/test/Calculator/LuhnTest.php b/test/Calculator/LuhnTest.php
index caf9f96431..4711dc2f07 100644
--- a/test/Calculator/LuhnTest.php
+++ b/test/Calculator/LuhnTest.php
@@ -33,7 +33,7 @@ public function checkDigitProvider()
     public function testComputeCheckDigit($partialNumber, $checkDigit): void
     {
         self::assertIsString($checkDigit);
-        self::assertEquals($checkDigit, Luhn::computeCheckDigit($partialNumber));
+        self::assertEquals($checkDigit, Luhn::computeCheckDigit((string) $partialNumber));
     }
 
     public function validatorProvider()
@@ -59,7 +59,7 @@ public function validatorProvider()
      */
     public function testIsValid($number, $isValid): void
     {
-        self::assertEquals($isValid, Luhn::isValid($number));
+        self::assertEquals($isValid, Luhn::isValid((string) $number));
     }
 
     public function testGenerateLuhnNumberWithInvalidPrefix(): void
diff --git a/test/Provider/BaseTest.php b/test/Provider/BaseTest.php
index 73e685a961..8a2e88d94c 100644
--- a/test/Provider/BaseTest.php
+++ b/test/Provider/BaseTest.php
@@ -90,7 +90,7 @@ public function testRandomFloat(): void
 
         $result = BaseProvider::randomFloat($nbMaxDecimals, $min, $max);
 
-        $parts = explode('.', $result);
+        $parts = explode('.', (string) $result);
 
         self::assertIsFloat($result);
         self::assertGreaterThanOrEqual($min, $result);
diff --git a/test/Provider/nl_BE/PaymentTest.php b/test/Provider/nl_BE/PaymentTest.php
index c8680248f7..8631682afd 100644
--- a/test/Provider/nl_BE/PaymentTest.php
+++ b/test/Provider/nl_BE/PaymentTest.php
@@ -34,7 +34,7 @@ private function validateChecksum($vat): void
         self::assertStringStartsWith('0', $numbers);
 
         // Mod97 check on first 8 digits
-        $checksum = 97 - fmod(substr($numbers, 0, 8), 97);
+        $checksum = 97 - fmod((float) substr($numbers, 0, 8), 97);
         // Make sure checksum is 2 characters long
         $checksum = sprintf('%02d', $checksum);
 
diff --git a/test/Provider/ro_RO/PersonTest.php b/test/Provider/ro_RO/PersonTest.php
index 229a14d680..ad4e86a72a 100644
--- a/test/Provider/ro_RO/PersonTest.php
+++ b/test/Provider/ro_RO/PersonTest.php
@@ -209,7 +209,7 @@ protected function isValidMaleCnp($value)
     protected function isValidCnp($cnp)
     {
         if (preg_match(self::TEST_CNP_REGEX, $cnp) !== false) {
-            $checkNumber = 279146358279;
+            $checkNumber = '279146358279';
 
             $checksum = 0;