diff --git a/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/Fixture/rename.php.inc b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/Fixture/rename.php.inc
new file mode 100644
index 00000000..415cd038
--- /dev/null
+++ b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/Fixture/rename.php.inc
@@ -0,0 +1,37 @@
+<?php
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithCamelCaseRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class RenameTest extends TestCase
+{
+    public function test_me()
+    {
+    }
+
+    public function test_this_is_a_long_test_case()
+    {
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithCamelCaseRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class RenameTest extends TestCase
+{
+    public function testMe()
+    {
+    }
+
+    public function testThisIsALongTestCase()
+    {
+    }
+}
+
+?>
diff --git a/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/Fixture/skip_existing_name.php.inc b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/Fixture/skip_existing_name.php.inc
new file mode 100644
index 00000000..c001f833
--- /dev/null
+++ b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/Fixture/skip_existing_name.php.inc
@@ -0,0 +1,16 @@
+<?php
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithCamelCaseRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class SkipExistingNameTest extends TestCase
+{
+    public function test_me()
+    {
+    }
+
+    public function testMe()
+    {
+    }
+}
diff --git a/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/PreferTestsWithCamelCaseRectorTest.php b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/PreferTestsWithCamelCaseRectorTest.php
new file mode 100644
index 00000000..62b56edf
--- /dev/null
+++ b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/PreferTestsWithCamelCaseRectorTest.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithCamelCaseRector;
+
+use Iterator;
+use PHPUnit\Framework\Attributes\DataProvider;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+final class PreferTestsWithCamelCaseRectorTest extends AbstractRectorTestCase
+{
+    #[DataProvider('provideData')]
+    public function test(string $filePath): void
+    {
+        $this->doTestFile($filePath);
+    }
+
+    public static function provideData(): Iterator
+    {
+        return self::yieldFilesFromDirectory(__DIR__ . '/Fixture');
+    }
+
+    public function provideConfigFilePath(): string
+    {
+        return __DIR__ . '/config/configured_rule.php';
+    }
+}
diff --git a/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/config/configured_rule.php b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/config/configured_rule.php
new file mode 100644
index 00000000..641703e9
--- /dev/null
+++ b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector/config/configured_rule.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\PHPUnit\CodeQuality\Rector\Class_\PreferTestsWithCamelCaseRector;
+
+return static function (RectorConfig $rectorConfig): void {
+    $rectorConfig->rule(PreferTestsWithCamelCaseRector::class);
+};
diff --git a/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/Fixture/rename.php.inc b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/Fixture/rename.php.inc
new file mode 100644
index 00000000..4a25ebed
--- /dev/null
+++ b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/Fixture/rename.php.inc
@@ -0,0 +1,37 @@
+<?php
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithSnakeCaseRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class RenameTest extends TestCase
+{
+    public function testMe()
+    {
+    }
+
+    public function testThisIsALongTestCase()
+    {
+    }
+}
+
+?>
+-----
+<?php
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithSnakeCaseRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class RenameTest extends TestCase
+{
+    public function test_me()
+    {
+    }
+
+    public function test_this_is_a_long_test_case()
+    {
+    }
+}
+
+?>
diff --git a/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/Fixture/skip_existing_name.php.inc b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/Fixture/skip_existing_name.php.inc
new file mode 100644
index 00000000..748670a0
--- /dev/null
+++ b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/Fixture/skip_existing_name.php.inc
@@ -0,0 +1,16 @@
+<?php
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithSnakeCaseRector\Fixture;
+
+use PHPUnit\Framework\TestCase;
+
+final class SkipExistingNameTest extends TestCase
+{
+    public function testMe()
+    {
+    }
+
+    public function test_me()
+    {
+    }
+}
diff --git a/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/PreferTestsWithSnakeCaseRectorTest.php b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/PreferTestsWithSnakeCaseRectorTest.php
new file mode 100644
index 00000000..2a21d476
--- /dev/null
+++ b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/PreferTestsWithSnakeCaseRectorTest.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithSnakeCaseRector;
+
+use Iterator;
+use PHPUnit\Framework\Attributes\DataProvider;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+final class PreferTestsWithSnakeCaseRectorTest extends AbstractRectorTestCase
+{
+    #[DataProvider('provideData')]
+    public function test(string $filePath): void
+    {
+        $this->doTestFile($filePath);
+    }
+
+    public static function provideData(): Iterator
+    {
+        return self::yieldFilesFromDirectory(__DIR__ . '/Fixture');
+    }
+
+    public function provideConfigFilePath(): string
+    {
+        return __DIR__ . '/config/configured_rule.php';
+    }
+}
diff --git a/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/config/configured_rule.php b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/config/configured_rule.php
new file mode 100644
index 00000000..0232f132
--- /dev/null
+++ b/rules-tests/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector/config/configured_rule.php
@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\PHPUnit\CodeQuality\Rector\Class_\PreferTestsWithSnakeCaseRector;
+
+return static function (RectorConfig $rectorConfig): void {
+    $rectorConfig->rule(PreferTestsWithSnakeCaseRector::class);
+};
diff --git a/rules/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector.php b/rules/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector.php
new file mode 100644
index 00000000..0a4d5f29
--- /dev/null
+++ b/rules/CodeQuality/Rector/Class_/PreferTestsWithCamelCaseRector.php
@@ -0,0 +1,107 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\PHPUnit\CodeQuality\Rector\Class_;
+
+use PhpParser\Node;
+use PhpParser\Node\Stmt\Class_;
+use Rector\PHPUnit\NodeAnalyzer\TestsNodeAnalyzer;
+use Rector\Rector\AbstractRector;
+use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
+use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;
+
+/**
+ * @see \Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithCamelCaseRector\PreferTestsWithCamelCaseRectorTest
+ */
+final class PreferTestsWithCamelCaseRector extends AbstractRector
+{
+    public function __construct(
+        private readonly TestsNodeAnalyzer $testsNodeAnalyzer,
+    ) {
+    }
+
+    public function getRuleDefinition(): RuleDefinition
+    {
+        return new RuleDefinition('Changes PHPUnit test methods to camel case', [
+            new CodeSample(
+                <<<'CODE_SAMPLE'
+use PHPUnit\Framework\TestCase;
+
+final class SomeClass extends TestCase
+{
+    public function test_something()
+    {
+    }
+}
+CODE_SAMPLE
+                ,
+                <<<'CODE_SAMPLE'
+use PHPUnit\Framework\TestCase;
+
+final class SomeClass extends TestCase
+{
+    public function testSomething()
+    {
+    }
+}
+CODE_SAMPLE
+            ),
+        ]);
+    }
+
+    /**
+     * @return array<class-string<Node>>
+     */
+    public function getNodeTypes(): array
+    {
+        return [Class_::class];
+    }
+
+    /**
+     * @param Class_ $node
+     */
+    public function refactor(Node $node): ?Node
+    {
+        if (! $this->testsNodeAnalyzer->isInTestClass($node)) {
+            return null;
+        }
+
+        $hasChanged = false;
+
+        foreach ($node->getMethods() as $classMethod) {
+            if (! $this->testsNodeAnalyzer->isTestClassMethod($classMethod)) {
+                continue;
+            }
+
+            $currentName = $classMethod->name->toString();
+            $newName = $this->toCamelCase($currentName);
+
+            if ($currentName === $newName) {
+                continue;
+            }
+
+            // avoid name collision with an existing method
+            if ($node->getMethod($newName) instanceof Node) {
+                continue;
+            }
+
+            $classMethod->name = new Node\Identifier($newName);
+            $hasChanged = true;
+        }
+
+        if ($hasChanged === false) {
+            return null;
+        }
+
+        return $node;
+    }
+
+    private function toCamelCase(string $value): string
+    {
+        $words = explode(' ', str_replace(['-', '_'], ' ', $value));
+        $words = array_map(fn (string $word): string => ucfirst($word), $words);
+
+        return lcfirst(implode($words));
+    }
+}
diff --git a/rules/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector.php b/rules/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector.php
new file mode 100644
index 00000000..6e5a3838
--- /dev/null
+++ b/rules/CodeQuality/Rector/Class_/PreferTestsWithSnakeCaseRector.php
@@ -0,0 +1,111 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\PHPUnit\CodeQuality\Rector\Class_;
+
+use PhpParser\Node;
+use PhpParser\Node\Stmt\Class_;
+use Rector\PHPUnit\NodeAnalyzer\TestsNodeAnalyzer;
+use Rector\Rector\AbstractRector;
+use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
+use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;
+
+/**
+ * @see \Rector\PHPUnit\Tests\CodeQuality\Rector\Class_\PreferTestsWithSnakeCaseRector\PreferTestsWithSnakeCaseRectorTest
+ */
+final class PreferTestsWithSnakeCaseRector extends AbstractRector
+{
+    public function __construct(
+        private readonly TestsNodeAnalyzer $testsNodeAnalyzer,
+    ) {
+    }
+
+    public function getRuleDefinition(): RuleDefinition
+    {
+        return new RuleDefinition('Changes PHPUnit test methods to snake case', [
+            new CodeSample(
+                <<<'CODE_SAMPLE'
+use PHPUnit\Framework\TestCase;
+
+final class SomeClass extends TestCase
+{
+    public function testSomething()
+    {
+    }
+}
+CODE_SAMPLE
+                ,
+                <<<'CODE_SAMPLE'
+use PHPUnit\Framework\TestCase;
+
+final class SomeClass extends TestCase
+{
+    public function test_something()
+    {
+    }
+}
+CODE_SAMPLE
+            ),
+        ]);
+    }
+
+    /**
+     * @return array<class-string<Node>>
+     */
+    public function getNodeTypes(): array
+    {
+        return [Class_::class];
+    }
+
+    /**
+     * @param Class_ $node
+     */
+    public function refactor(Node $node): ?Node
+    {
+        if (! $this->testsNodeAnalyzer->isInTestClass($node)) {
+            return null;
+        }
+
+        $hasChanged = false;
+
+        foreach ($node->getMethods() as $classMethod) {
+            if (! $this->testsNodeAnalyzer->isTestClassMethod($classMethod)) {
+                continue;
+            }
+
+            $currentName = $classMethod->name->toString();
+            $newName = $this->toSnakeCase($currentName);
+
+            if ($currentName === $newName) {
+                continue;
+            }
+
+            // avoid name collision with an existing method
+            if ($node->getMethod($newName) instanceof Node) {
+                continue;
+            }
+
+            $classMethod->name = new Node\Identifier($newName);
+            $hasChanged = true;
+        }
+
+        if ($hasChanged === false) {
+            return null;
+        }
+
+        return $node;
+    }
+
+    private function toSnakeCase(string $value): string
+    {
+        if (ctype_lower($value)) {
+            return $value;
+        }
+
+        $value = (string) preg_replace('/\s+/u', '', ucwords($value));
+        $value = (string) preg_replace('/(.)(?=[A-Z])/u', '$1_', $value);
+
+        return strtolower($value);
+    }
+}