diff --git a/phpstan.neon b/phpstan.neon
index 362ba447..ebd4bf30 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -4,7 +4,7 @@ includes:
     - vendor/thecodingmachine/phpstan-strict-rules/phpstan-strict-rules.neon
 
 parameters:
-    level: 8
+    level: 9
     paths:
         - src
 
diff --git a/src/Datasets.php b/src/Datasets.php
index c91de5e7..7f8013fe 100644
--- a/src/Datasets.php
+++ b/src/Datasets.php
@@ -98,7 +98,8 @@ final class Datasets
 
             foreach ($datasetCombination as $dataset_data) {
                 $partialDescriptions[] = $dataset_data['label'];
-                $values                = array_merge($values, $dataset_data['values']);
+                //@phpstan-ignore-next-line
+                $values = array_merge($values, $dataset_data['values']);
             }
 
             $dataSetDescriptions[] = $description . ' with ' . implode(' / ', $partialDescriptions);
@@ -152,10 +153,11 @@ final class Datasets
                 $datasets[$index] = iterator_to_array($datasets[$index]);
             }
 
+            //@phpstan-ignore-next-line
             foreach ($datasets[$index] as $key => $values) {
                 $values             = is_array($values) ? $values : [$values];
                 $processedDataset[] = [
-                    'label'  => self::getDataSetDescription($key, $values),
+                    'label'  => self::getDataSetDescription($key, $values), //@phpstan-ignore-line
                     'values' => $values,
                 ];
             }
@@ -169,7 +171,7 @@ final class Datasets
     /**
      * @param array<array<mixed>> $combinations
      *
-     * @return array<array<mixed>>
+     * @return array<array<array<mixed>>>
      */
     private static function getDataSetsCombinations(array $combinations): array
     {
@@ -184,6 +186,7 @@ final class Datasets
             $result = $tmp;
         }
 
+        //@phpstan-ignore-next-line
         return $result;
     }
 
diff --git a/src/Exceptions/ExpectationException.php b/src/Exceptions/ExpectationException.php
index ca14ce76..be68b40c 100644
--- a/src/Exceptions/ExpectationException.php
+++ b/src/Exceptions/ExpectationException.php
@@ -9,8 +9,13 @@ namespace Pest\Exceptions;
  */
 final class ExpectationException extends \Exception
 {
-    public static function invalidValue(string $expectationName, string $valueRequired): ExpectationException
+    public static function invalidCurrentValueType(string $expectationName, string $valueRequired): ExpectationException
     {
         return new ExpectationException(sprintf('%s expectation requires a %s value.', $expectationName, $valueRequired));
     }
+
+    public static function invalidExpectedValueType(string $expectationName, string $valueRequired): ExpectationException
+    {
+        return new ExpectationException(sprintf('%s expectation requires a %s as expected value.', $expectationName, $valueRequired));
+    }
 }
diff --git a/src/Expectation.php b/src/Expectation.php
index dada9447..5ee04b0b 100644
--- a/src/Expectation.php
+++ b/src/Expectation.php
@@ -70,7 +70,7 @@ final class Expectation
     public function json(): Expectation
     {
         if (!is_string($this->value)) {
-            throw ExpectationException::invalidValue('json', 'string');
+            throw ExpectationException::invalidCurrentValueType('json', 'string');
         }
 
         return $this->toBeJson()->and(json_decode($this->value, true));
@@ -360,8 +360,14 @@ final class Expectation
     {
         foreach ($needles as $needle) {
             if (is_string($this->value)) {
+                if (!is_string($needle)) {
+                    throw ExpectationException::invalidExpectedValueType('toContain', 'string');
+                }
                 Assert::assertStringContainsString($needle, $this->value);
             } else {
+                if (!is_iterable($this->value)) {
+                    throw ExpectationException::invalidCurrentValueType('toContain', 'iterable');
+                }
                 Assert::assertContains($needle, $this->value);
             }
         }
@@ -376,6 +382,10 @@ final class Expectation
      */
     public function toStartWith(string $expected): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toStartWith', 'string');
+        }
+
         Assert::assertStringStartsWith($expected, $this->value);
 
         return $this;
@@ -388,6 +398,10 @@ final class Expectation
      */
     public function toEndWith(string $expected): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toEndWith', 'string');
+        }
+
         Assert::assertStringEndsWith($expected, $this->value);
 
         return $this;
@@ -428,6 +442,10 @@ final class Expectation
      */
     public function toHaveCount(int $count): Expectation
     {
+        if (!is_countable($this->value) && !is_iterable($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toHaveCount', 'string');
+        }
+
         Assert::assertCount($count, $this->value);
 
         return $this;
@@ -440,6 +458,7 @@ final class Expectation
     {
         $this->toBeObject();
 
+        //@phpstan-ignore-next-line
         Assert::assertTrue(property_exists($this->value, $name));
 
         if (func_num_args() > 1) {
@@ -651,6 +670,8 @@ final class Expectation
     public function toBeJson(): Expectation
     {
         Assert::assertIsString($this->value);
+
+        //@phpstan-ignore-next-line
         Assert::assertJson($this->value);
 
         return $this;
@@ -721,6 +742,10 @@ final class Expectation
      */
     public function toBeDirectory(): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toBeDirectory', 'string');
+        }
+
         Assert::assertDirectoryExists($this->value);
 
         return $this;
@@ -731,6 +756,10 @@ final class Expectation
      */
     public function toBeReadableDirectory(): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toBeReadableDirectory', 'string');
+        }
+
         Assert::assertDirectoryIsReadable($this->value);
 
         return $this;
@@ -741,6 +770,10 @@ final class Expectation
      */
     public function toBeWritableDirectory(): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toBeWritableDirectory', 'string');
+        }
+
         Assert::assertDirectoryIsWritable($this->value);
 
         return $this;
@@ -751,6 +784,10 @@ final class Expectation
      */
     public function toBeFile(): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toBeFile', 'string');
+        }
+
         Assert::assertFileExists($this->value);
 
         return $this;
@@ -761,6 +798,9 @@ final class Expectation
      */
     public function toBeReadableFile(): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toBeReadableFile', 'string');
+        }
         Assert::assertFileIsReadable($this->value);
 
         return $this;
@@ -771,6 +811,9 @@ final class Expectation
      */
     public function toBeWritableFile(): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toBeWritableFile', 'string');
+        }
         Assert::assertFileIsWritable($this->value);
 
         return $this;
@@ -815,6 +858,9 @@ final class Expectation
     public function toMatchObject(iterable|object $object): Expectation
     {
         foreach ((array) $object as $property => $value) {
+            if (!is_object($this->value) && !is_string($this->value)) {
+                throw ExpectationException::invalidCurrentValueType('toMatchObject', 'object|string');
+            }
             Assert::assertTrue(property_exists($this->value, $property));
 
             /* @phpstan-ignore-next-line */
@@ -838,6 +884,9 @@ final class Expectation
      */
     public function toMatch(string $expression): Expectation
     {
+        if (!is_string($this->value)) {
+            throw ExpectationException::invalidCurrentValueType('toMatch', 'string');
+        }
         Assert::assertMatchesRegularExpression($expression, $this->value);
 
         return $this;
@@ -897,10 +946,10 @@ final class Expectation
         }
 
         if (!class_exists($exception)) {
-            throw new ExpectationFailedException("Exception with message \"{$exception}\" not thrown.");
+            throw new ExpectationFailedException("Exception with message \"$exception\" not thrown.");
         }
 
-        throw new ExpectationFailedException("Exception \"{$exception}\" not thrown.");
+        throw new ExpectationFailedException("Exception \"$exception\" not thrown.");
     }
 
     /**
@@ -925,7 +974,7 @@ final class Expectation
      */
     public function __call(string $method, array $parameters)
     {
-        if (!static::hasExtend($method)) {
+        if (!Expectation::hasExtend($method)) {
             /* @phpstan-ignore-next-line */
             return new HigherOrderExpectation($this, $this->value->$method(...$parameters));
         }
@@ -939,7 +988,8 @@ final class Expectation
      */
     public function __get(string $name): Expectation|OppositeExpectation|Each|HigherOrderExpectation
     {
-        if (!method_exists($this, $name) && !static::hasExtend($name)) {
+        if (!method_exists($this, $name) && !Expectation::hasExtend($name)) {
+            //@phpstan-ignore-next-line
             return new HigherOrderExpectation($this, $this->retrieve($name, $this->value));
         }
 
diff --git a/src/Support/Container.php b/src/Support/Container.php
index 57b82f54..1f6b45cd 100644
--- a/src/Support/Container.php
+++ b/src/Support/Container.php
@@ -37,7 +37,7 @@ final class Container
      *
      * @param class-string $id
      *
-     * @return object
+     * @return mixed
      */
     public function get(string $id)
     {
diff --git a/src/Support/HigherOrderMessageCollection.php b/src/Support/HigherOrderMessageCollection.php
index cb69a3a9..54bef82a 100644
--- a/src/Support/HigherOrderMessageCollection.php
+++ b/src/Support/HigherOrderMessageCollection.php
@@ -40,6 +40,7 @@ final class HigherOrderMessageCollection
     public function chain(object $target): void
     {
         foreach ($this->messages as $message) {
+            //@phpstan-ignore-next-line
             $target = $message->call($target) ?? $target;
         }
     }