diff --git a/phpstan.neon b/phpstan.neon
index cb841bf..824d929 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -16,6 +16,11 @@ services:
     - Rector\Skipper\Fnmatcher
     - Rector\Skipper\RealpathMatcher
 
+    -
+        class: BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\TestsExtendMockeryTestCaseRule
+        tags:
+            - phpstan.rules.rule
+
 parameters:
     level: max
     paths:
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/TestsExtendMockeryTestCaseRule.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/TestsExtendMockeryTestCaseRule.php
new file mode 100644
index 0000000..76276c1
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/TestsExtendMockeryTestCaseRule.php
@@ -0,0 +1,89 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule;
+
+use Mockery\Adapter\Phpunit\MockeryTestCase;
+use PhpParser\Node;
+use PhpParser\Node\Stmt\Class_;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\ReflectionProvider;
+use PHPStan\Rules\IdentifierRuleError;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use PHPStan\Testing\RuleTestCase;
+use PHPUnit\Framework\TestCase;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+use SlevomatCodingStandard\Sniffs\TestCase as SlevomatCodingStandardTestCase;
+use function sprintf;
+
+/**
+ * @implements Rule<Class_>
+ */
+class TestsExtendMockeryTestCaseRule implements Rule
+{
+    public function __construct(
+        private readonly ReflectionProvider $reflectionProvider,
+    ) {
+    }
+
+
+    public function getNodeType(): string
+    {
+        return Class_::class;
+    }
+
+
+    /**
+     * @param Class_ $node
+     *
+     * @return list<IdentifierRuleError>
+     */
+    public function processNode(Node $node, Scope $scope): array
+    {
+        if ($node->name === null || $node->isAbstract()) {
+            return [];
+        }
+
+        $namespacedName = $node->namespacedName;
+
+        if ($namespacedName === null) {
+            return [];
+        }
+
+        $className = $scope->resolveName($namespacedName);
+
+        if (!$this->reflectionProvider->hasClass($className)) {
+            return [];
+        }
+
+        $class = $this->reflectionProvider->getClass($className);
+
+        if (!$class->isSubclassOf(TestCase::class)) {
+            return [];
+        }
+
+        // Allow these code quality tools test cases as they are not using Mockery
+        if ($class->isSubclassOf(SlevomatCodingStandardTestCase::class)
+            || $class->isSubclassOf(AbstractRectorTestCase::class)
+            || $class->isSubclassOf(RuleTestCase::class)) {
+            return [];
+        }
+
+        if ($class->isSubclassOf(MockeryTestCase::class)) {
+            return [];
+        }
+
+        $ruleErrorMessage = sprintf(
+            'PHPUnit test %s must extend %s (directly or indirectly).',
+            $class->getName(),
+            MockeryTestCase::class,
+        );
+
+        return [
+            RuleErrorBuilder::message($ruleErrorMessage)
+                ->identifier('mockery.testCase')
+                ->nonIgnorable()
+                ->build(),
+        ];
+    }
+}
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/TestsExtendMockeryTestCaseRuleTest.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/TestsExtendMockeryTestCaseRuleTest.php
new file mode 100644
index 0000000..aba47d7
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/TestsExtendMockeryTestCaseRuleTest.php
@@ -0,0 +1,90 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<TestsExtendMockeryTestCaseRule>
+ */
+class TestsExtendMockeryTestCaseRuleTest extends RuleTestCase
+{
+    protected function getRule(): Rule
+    {
+        return new TestsExtendMockeryTestCaseRule($this->createReflectionProvider());
+    }
+
+
+    public function testExtendsMockeryTestCase(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/__fixtures__/TestExtendsMockeryTestCase.php'],
+            [],
+        );
+    }
+
+
+    public function testExtendsClassWhichExtendsMockeryTestCase(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/__fixtures__/TestExtendsClassWhichExtendsMockeryTestCase.php'],
+            [],
+        );
+    }
+
+
+    public function testExtendsPhpUnitTestCase(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/__fixtures__/TestExtendsPhpUnitTestCase.php'],
+            [
+                [
+                    'PHPUnit test BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__\TestExtendsPhpUnitTestCase must extend Mockery\Adapter\Phpunit\MockeryTestCase (directly or indirectly).',
+                    7,
+                ],
+            ],
+        );
+    }
+
+
+    public function testExtendsClassWhichExtendsPhpUnitTestCase(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/__fixtures__/TestExtendsClassWhichExtendsPhpUnitTestCase.php'],
+            [
+                [
+                    'PHPUnit test BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__\TestExtendsClassWhichExtendsPhpUnitTestCase must extend Mockery\Adapter\Phpunit\MockeryTestCase (directly or indirectly).',
+                    5,
+                ],
+            ],
+        );
+    }
+
+
+    public function testExtendsPhpstanRuleTestCase(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/__fixtures__/TestExtendsPhpstanRuleTestCase.php'],
+            [],
+        );
+    }
+
+
+    public function testExtendsRectorRuleTestCase(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/__fixtures__/TestExtendsRectorRuleTestCase.php'],
+            [],
+        );
+    }
+
+
+    public function testExtendsSlevomatCodingStandardTestCase(): void
+    {
+        $this->analyse(
+            [__DIR__ . '/__fixtures__/TestExtendsSlevomatCodingStandardTestCase.php'],
+            [],
+        );
+    }
+}
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsClassWhichExtendsMockeryTestCase.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsClassWhichExtendsMockeryTestCase.php
new file mode 100644
index 0000000..def7c55
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsClassWhichExtendsMockeryTestCase.php
@@ -0,0 +1,7 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__;
+
+class TestExtendsClassWhichExtendsMockeryTestCase extends TestExtendsMockeryTestCase
+{
+}
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsClassWhichExtendsPhpUnitTestCase.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsClassWhichExtendsPhpUnitTestCase.php
new file mode 100644
index 0000000..4c55cbb
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsClassWhichExtendsPhpUnitTestCase.php
@@ -0,0 +1,7 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__;
+
+class TestExtendsClassWhichExtendsPhpUnitTestCase extends TestExtendsPhpUnitTestCase
+{
+}
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsMockeryTestCase.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsMockeryTestCase.php
new file mode 100644
index 0000000..c38c81c
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsMockeryTestCase.php
@@ -0,0 +1,9 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__;
+
+use Mockery\Adapter\Phpunit\MockeryTestCase;
+
+class TestExtendsMockeryTestCase extends MockeryTestCase
+{
+}
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsPhpUnitTestCase.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsPhpUnitTestCase.php
new file mode 100644
index 0000000..6d51fc7
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsPhpUnitTestCase.php
@@ -0,0 +1,9 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__;
+
+use PHPUnit\Framework\TestCase;
+
+class TestExtendsPhpUnitTestCase extends TestCase
+{
+}
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsPhpstanRuleTestCase.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsPhpstanRuleTestCase.php
new file mode 100644
index 0000000..b04537c
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsPhpstanRuleTestCase.php
@@ -0,0 +1,9 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__;
+
+use PHPStan\Testing\RuleTestCase;
+
+class TestExtendsPhpstanRuleTestCase extends RuleTestCase
+{
+}
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsRectorRuleTestCase.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsRectorRuleTestCase.php
new file mode 100644
index 0000000..f9d6c65
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsRectorRuleTestCase.php
@@ -0,0 +1,13 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__;
+
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+class TestExtendsRectorRuleTestCase extends AbstractRectorTestCase
+{
+    public function provideConfigFilePath(): string
+    {
+        return '';
+    }
+}
diff --git a/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsSlevomatCodingStandardTestCase.php b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsSlevomatCodingStandardTestCase.php
new file mode 100644
index 0000000..c2cdfd3
--- /dev/null
+++ b/src/BrandEmbassyCodingStandard/PhpStan/Rules/Mockery/TestsExtendMockeryTestCaseRule/__fixtures__/TestExtendsSlevomatCodingStandardTestCase.php
@@ -0,0 +1,9 @@
+<?php declare(strict_types = 1);
+
+namespace BrandEmbassyCodingStandard\PhpStan\Rules\Mockery\TestsExtendMockeryTestCaseRule\__fixtures__;
+
+use SlevomatCodingStandard\Sniffs\TestCase;
+
+class TestExtendsSlevomatCodingStandardTestCase extends TestCase
+{
+}