Enforce the use of "@covers" annotation

Signed-off-by: Henrique Moody <henriquemoody@gmail.com>

.php_cs

@@ -26,6 +26,7 @@ return PhpCsFixer\Config::create()
             'style' => 'annotation',
         ],
         'php_unit_test_case_static_method_calls' => ['call_type' => 'self'],
+        'php_unit_test_class_requires_covers' => true,
     ])
     ->setCacheFile(
         sprintf(

tests/unit/Exceptions/CheckExceptionsTest.php

@@ -17,6 +17,9 @@ use DirectoryIterator;
 use PHPUnit\Framework\TestCase;
 use ReflectionClass;
 
+/**
+ * @coversNothing
+ */
 class CheckExceptionsTest extends TestCase
 {
     protected $deprecateds = [];

tests/unit/Exceptions/NestedValidationExceptionTest.php

@@ -15,6 +15,9 @@ namespace Respect\Validation\Exceptions;
 
 use PHPUnit\Framework\TestCase;
 
+/**
+ * @covers \Respect\Validation\Exceptions\NestedValidationException
+ */
 class NestedValidationExceptionTest extends TestCase
 {
     /**

tests/unit/Rules/AbstractCompositeTest.php

@@ -16,6 +16,9 @@ namespace Respect\Validation\Rules;
 use PHPUnit\Framework\TestCase;
 use Respect\Validation\Validatable;
 
+/**
+ * @covers \Respect\Validation\Rules\AbstractComposite
+ */
 class AbstractCompositeTest extends TestCase
 {
     /**

tests/unit/Rules/AbstractCtypeRuleTest.php

@@ -15,6 +15,9 @@ namespace Respect\Validation\Rules;
 
 use PHPUnit\Framework\TestCase;
 
+/**
+ * @covers \Respect\Validation\Rules\AbstractCtypeRule
+ */
 class AbstractCtypeRuleTest extends TestCase
 {
     /**

tests/unit/Rules/AbstractFilterRuleTest.php

@@ -15,6 +15,9 @@ namespace Respect\Validation\Rules;
 
 use PHPUnit\Framework\TestCase;
 
+/**
+ * @covers \Respect\Validation\Rules\AbstractFilterRule
+ */
 class AbstractFilterRuleTest extends TestCase
 {
     /**

tests/unit/Rules/AbstractRegexRuleTest.php

@@ -15,6 +15,9 @@ namespace Respect\Validation\Rules;
 
 use PHPUnit\Framework\TestCase;
 
+/**
+ * @covers \Respect\Validation\Rules\AbstractRegexRule
+ */
 class AbstractRegexRuleTest extends TestCase
 {
     /**

tests/unit/Rules/AbstractRelatedTest.php

@@ -16,6 +16,9 @@ namespace Respect\Validation\Rules;
 use PHPUnit\Framework\TestCase;
 use Respect\Validation\Validatable;
 
+/**
+ * @covers \Respect\Validation\Rules\AbstractRelated
+ */
 final class AbstractRelatedTest extends TestCase
 {
     public function providerForOperations()

tests/unit/Rules/AbstractRuleTest.php

@@ -16,6 +16,9 @@ namespace Respect\Validation\Rules;
 use PHPUnit\Framework\TestCase;
 use Respect\Validation\Exceptions\ValidationException;
 
+/**
+ * @covers \Respect\Validation\Rules\AbstractRule
+ */
 class AbstractRuleTest extends TestCase
 {
     public function providerForTrueAndFalse()

tests/unit/Rules/AbstractSearcherTest.php

@@ -19,6 +19,8 @@ use Respect\Validation\Test\DataProvider\UndefinedProvider;
 /**
  * @group core
  *
+ * @covers \Respect\Validation\Rules\AbstractSearcher
+ *
  * @author Henrique Moody <henriquemoody@gmail.com>
  */
 final class AbstractSearcherTest extends TestCase

tests/unit/ValidatorTest.php

@@ -16,6 +16,9 @@ namespace Respect\Validation;
 use PHPUnit\Framework\TestCase;
 use Respect\Validation\Exceptions\ComponentException;
 
+/**
+ * @covers \Respect\Validation\Validator
+ */
 class ValidatorTest extends TestCase
 {
     /**