Complete PHPStan Level 6 (#5305)

* Complete PHPStan Level 6
Fix https://github.com/FreshRSS/FreshRSS/issues/4112
And initiate PHPStan Level 7

* PHPStan Level 6 for tests
* Use phpstan/phpstan-phpunit
* Update to PHPStan version 1.10

* Fix mixed bug

* Fix mixed return bug

* Fix paginator bug

* Fix FreshRSS_UserConfiguration

* A couple more Minz_Configuration bug fixes

* A few trivial PHPStan Level 7 fixes

* A few more simple PHPStan Level 7

* More files passing PHPStan Level 7
Add interface to replace removed class from https://github.com/FreshRSS/FreshRSS/pull/5251

* A few more PHPStan Level 7 preparations

* A few last details

5 files changed, 62 insertions, 57 deletions

diff --git a/tests/cli/i18n/I18nCompletionValidatorTest.php b/tests/cli/i18n/I18nCompletionValidatorTest.php
index 1aa871f20..1a361823d 100644
--- a/tests/cli/i18n/I18nCompletionValidatorTest.php
+++ b/tests/cli/i18n/I18nCompletionValidatorTest.php
@@ -4,6 +4,7 @@ require_once __DIR__ . '/../../../cli/i18n/I18nCompletionValidator.php';
 require_once __DIR__ . '/../../../cli/i18n/I18nValue.php';
 
 class I18nCompletionValidatorTest extends PHPUnit\Framework\TestCase {
+	/** @var I18nValue&PHPUnit\Framework\MockObject\MockObject */
 	private $value;
 
 	public function setUp(): void {
@@ -12,7 +13,7 @@ class I18nCompletionValidatorTest extends PHPUnit\Framework\TestCase {
 			->getMock();
 	}
 
-	public function testDisplayReport() {
+	public function testDisplayReport(): void {
 		$validator = new I18nCompletionValidator([], []);
 
 		$this->assertEquals("There is no data.\n", $validator->displayReport());
@@ -40,13 +41,13 @@ class I18nCompletionValidatorTest extends PHPUnit\Framework\TestCase {
 		$validator->displayReport();
 	}
 
-	public function testValidateWhenNoData() {
+	public function testValidateWhenNoData(): void {
 		$validator = new I18nCompletionValidator([], []);
 		$this->assertTrue($validator->validate());
 		$this->assertEquals('', $validator->displayResult());
 	}
 
-	public function testValidateWhenKeyIsMissing() {
+	public function testValidateWhenKeyIsMissing(): void {
 		$validator = new I18nCompletionValidator([
 			'file1.php' => [
 				'file1.l1.l2.k1' => $this->value,
@@ -60,7 +61,7 @@ class I18nCompletionValidatorTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals("Missing key file1.l1.l2.k1\nMissing key file2.l1.l2.k1\n", $validator->displayResult());
 	}
 
-	public function testValidateWhenKeyIsIgnored() {
+	public function testValidateWhenKeyIsIgnored(): void {
 		$this->value->expects($this->exactly(2))
 			->method('isIgnore')
 			->willReturn(true);
@@ -85,7 +86,7 @@ class I18nCompletionValidatorTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals('', $validator->displayResult());
 	}
 
-	public function testValidateWhenValueIsEqual() {
+	public function testValidateWhenValueIsEqual(): void {
 		$this->value->expects($this->exactly(2))
 			->method('isIgnore')
 			->willReturn(false);
@@ -113,7 +114,7 @@ class I18nCompletionValidatorTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals("Untranslated key file1.l1.l2.k1 - \nUntranslated key file2.l1.l2.k1 - \n", $validator->displayResult());
 	}
 
-	public function testValidateWhenValueIsDifferent() {
+	public function testValidateWhenValueIsDifferent(): void {
 		$this->value->expects($this->exactly(2))
 			->method('isIgnore')
 			->willReturn(false);
diff --git a/tests/cli/i18n/I18nDataTest.php b/tests/cli/i18n/I18nDataTest.php
index b27ad830c..37811c193 100644
--- a/tests/cli/i18n/I18nDataTest.php
+++ b/tests/cli/i18n/I18nDataTest.php
@@ -4,7 +4,9 @@ require_once __DIR__ . '/../../../cli/i18n/I18nData.php';
 require_once __DIR__ . '/../../../cli/i18n/I18nValue.php';
 
 class I18nDataTest extends PHPUnit\Framework\TestCase {
+	/** @var array<string,array<string,array<string,I18nValue>>> */
 	private $referenceData;
+	/** @var I18nValue&PHPUnit\Framework\MockObject\MockObject */
 	private $value;
 
 	public function setUp(): void {
@@ -31,12 +33,12 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		];
 	}
 
-	public function testConstructWhenReferenceOnly() {
+	public function testConstructWhenReferenceOnly(): void {
 		$data = new I18nData($this->referenceData);
 		$this->assertEquals($this->referenceData, $data->getData());
 	}
 
-	public function testConstructorWhenLanguageIsMissingFile() {
+	public function testConstructorWhenLanguageIsMissingFile(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [
 				'file1.php' => [
@@ -79,7 +81,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getData());
 	}
 
-	public function testConstructorWhenLanguageIsMissingKeys() {
+	public function testConstructorWhenLanguageIsMissingKeys(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [
 				'file1.php' => [
@@ -125,7 +127,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getData());
 	}
 
-	public function testConstructorWhenLanguageHasExtraKeys() {
+	public function testConstructorWhenLanguageHasExtraKeys(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [
 				'file1.php' => [
@@ -179,7 +181,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getData());
 	}
 
-	public function testConstructorWhenValueIsIdenticalAndIsMarkedAsIgnore() {
+	public function testConstructorWhenValueIsIdenticalAndIsMarkedAsIgnore(): void {
 		$value = $this->getMockBuilder(I18nValue::class)
 			->disableOriginalConstructor()
 			->getMock();
@@ -204,7 +206,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		new I18nData($rawData);
 	}
 
-	public function testConstructorWhenValueIsIdenticalAndIsNotMarkedAsIgnore() {
+	public function testConstructorWhenValueIsIdenticalAndIsNotMarkedAsIgnore(): void {
 		$value = $this->getMockBuilder(I18nValue::class)
 			->disableOriginalConstructor()
 			->getMock();
@@ -229,7 +231,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		new I18nData($rawData);
 	}
 
-	public function testConstructorWhenValueIsDifferentAndIsMarkedAsToDo() {
+	public function testConstructorWhenValueIsDifferentAndIsMarkedAsToDo(): void {
 		$value = $this->getMockBuilder(I18nValue::class)
 			->disableOriginalConstructor()
 			->getMock();
@@ -249,7 +251,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		new I18nData($rawData);
 	}
 
-	public function testConstructorWhenValueIsDifferentAndIsNotMarkedAsTodo() {
+	public function testConstructorWhenValueIsDifferentAndIsNotMarkedAsTodo(): void {
 		$value = $this->getMockBuilder(I18nValue::class)
 			->disableOriginalConstructor()
 			->getMock();
@@ -269,7 +271,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		new I18nData($rawData);
 	}
 
-	public function testGetAvailableLanguagesWhenTheyAreSorted() {
+	public function testGetAvailableLanguagesWhenTheyAreSorted(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [],
 			'nl' => [],
@@ -282,7 +284,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getAvailableLanguages());
 	}
 
-	public function testGetAvailableLanguagesWhenTheyAreNotSorted() {
+	public function testGetAvailableLanguagesWhenTheyAreNotSorted(): void {
 		$rawData = array_merge($this->referenceData, [
 			'nl' => [],
 			'fr' => [],
@@ -297,14 +299,14 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getAvailableLanguages());
 	}
 
-	public function testAddLanguageWhenLanguageExists() {
+	public function testAddLanguageWhenLanguageExists(): void {
 		$this->expectException(\Exception::class);
 		$this->expectExceptionMessage('The selected language already exist.');
 		$data = new I18nData($this->referenceData);
 		$data->addLanguage('en');
 	}
 
-	public function testAddLanguageWhenNoReferenceProvided() {
+	public function testAddLanguageWhenNoReferenceProvided(): void {
 		$data = new I18nData($this->referenceData);
 		$data->addLanguage('fr');
 		$this->assertEquals([
@@ -341,7 +343,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getData());
 	}
 
-	public function testAddLanguageWhenUnknownReferenceProvided() {
+	public function testAddLanguageWhenUnknownReferenceProvided(): void {
 		$data = new I18nData($this->referenceData);
 		$data->addLanguage('fr', 'unknown');
 		$this->assertEquals([
@@ -378,7 +380,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getData());
 	}
 
-	public function testAddLanguageWhenKnownReferenceProvided() {
+	public function testAddLanguageWhenKnownReferenceProvided(): void {
 		$data = new I18nData($this->referenceData);
 		$data->addLanguage('fr', 'en');
 		$this->assertEquals([
@@ -415,24 +417,24 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getData());
 	}
 
-	public function testIsKnownWhenKeyExists() {
+	public function testIsKnownWhenKeyExists(): void {
 		$data = new I18nData($this->referenceData);
 		$this->assertTrue($data->isKnown('file2.l1.l2.k2'));
 	}
 
-	public function testIsKnownWhenKeyDoesNotExist() {
+	public function testIsKnownWhenKeyDoesNotExist(): void {
 		$data = new I18nData($this->referenceData);
 		$this->assertFalse($data->isKnown('file2.l1.l2.k3'));
 	}
 
-	public function testAddKeyWhenKeyExists() {
+	public function testAddKeyWhenKeyExists(): void {
 		$this->expectException(\Exception::class);
 		$this->expectExceptionMessage('The selected key already exist.');
 		$data = new I18nData($this->referenceData);
 		$data->addKey('file2.l1.l2.k1', 'value');
 	}
 
-	public function testAddKeyWhenParentKeyExists() {
+	public function testAddKeyWhenParentKeyExists(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [],
 		]);
@@ -447,7 +449,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$this->assertTrue($data->isKnown('file2.l1.l2.k1.sk1'));
 	}
 
-	public function testAddKeyWhenKeyIsParent() {
+	public function testAddKeyWhenKeyIsParent(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [],
 		]);
@@ -462,7 +464,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$this->assertTrue($data->isKnown('file1.l1.l2.k2'));
 	}
 
-	public function testAddKey() {
+	public function testAddKey(): void {
 		$getTargetedValue = static function (I18nData $data, string $language) {
 			return $data->getData()[$language]['file2.php']['file2.l1.l2.k3'];
 		};
@@ -484,21 +486,21 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals($frValue, $enValue);
 	}
 
-	public function testAddValueWhenLanguageDoesNotExist() {
+	public function testAddValueWhenLanguageDoesNotExist(): void {
 		$this->expectException(\Exception::class);
 		$this->expectExceptionMessage('The selected language does not exist.');
 		$data = new I18nData($this->referenceData);
 		$data->addValue('file2.l1.l2.k2', 'new value', 'fr');
 	}
 
-	public function testAddValueWhenKeyDoesNotExist() {
+	public function testAddValueWhenKeyDoesNotExist(): void {
 		$this->expectException(\Exception::class);
 		$this->expectExceptionMessage('The selected key does not exist for the selected language.');
 		$data = new I18nData($this->referenceData);
 		$data->addValue('unknown key', 'new value', 'en');
 	}
 
-	public function testAddValueWhenLanguageIsReferenceAndValueInOtherLanguageHasNotChange() {
+	public function testAddValueWhenLanguageIsReferenceAndValueInOtherLanguageHasNotChange(): void {
 		$getTargetedValue = static function (I18nData $data, string $language) {
 			return $data->getData()[$language]['file2.php']['file2.l1.l2.k2'];
 		};
@@ -526,7 +528,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals('new value', $afterFrValue->getValue());
 	}
 
-	public function testAddValueWhenLanguageIsReferenceAndValueInOtherLanguageHasChange() {
+	public function testAddValueWhenLanguageIsReferenceAndValueInOtherLanguageHasChange(): void {
 		$getTargetedValue = static function (I18nData $data, string $language) {
 			return $data->getData()[$language]['file2.php']['file2.l1.l2.k2'];
 		};
@@ -561,7 +563,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals($value, $afterFrValue);
 	}
 
-	public function testAddValueWhenLanguageIsNotReference() {
+	public function testAddValueWhenLanguageIsNotReference(): void {
 		$getTargetedValue = static function (I18nData $data, string $language) {
 			return $data->getData()[$language]['file2.php']['file2.l1.l2.k2'];
 		};
@@ -583,21 +585,21 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals('new value', $afterFrValue->getValue());
 	}
 
-	public function testRemoveKeyWhenKeyDoesNotExist() {
+	public function testRemoveKeyWhenKeyDoesNotExist(): void {
 		$this->expectException(\Exception::class);
 		$this->expectExceptionMessage('The selected key does not exist.');
 		$data = new I18nData($this->referenceData);
 		$data->removeKey('Unknown key');
 	}
 
-	public function testRemoveKeyWhenKeyHasNoEmptySibling() {
+	public function testRemoveKeyWhenKeyHasNoEmptySibling(): void {
 		$this->expectException(\Exception::class);
 		$this->expectExceptionMessage('The selected key does not exist.');
 		$data = new I18nData($this->referenceData);
 		$data->removeKey('file1.l1.l2');
 	}
 
-	public function testRemoveKeyWhenKeyIsEmptySibling() {
+	public function testRemoveKeyWhenKeyIsEmptySibling(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [],
 		]);
@@ -635,7 +637,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getData());
 	}
 
-	public function testRemoveKeyWhenKeyIsTheOnlyChild() {
+	public function testRemoveKeyWhenKeyIsTheOnlyChild(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [],
 		]);
@@ -673,7 +675,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		], $data->getData());
 	}
 
-	public function testIgnore() {
+	public function testIgnore(): void {
 		$value = $this->getMockBuilder(I18nValue::class)
 			->disableOriginalConstructor()
 			->getMock();
@@ -695,7 +697,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$data->ignore('file1.l1.l2.k1', 'fr', false);
 	}
 
-	public function testIgnoreUnmodified() {
+	public function testIgnoreUnmodified(): void {
 		$value = $this->getMockBuilder(I18nValue::class)
 			->disableOriginalConstructor()
 			->getMock();
@@ -722,7 +724,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$data->ignore_unmodified('fr', false);
 	}
 
-	public function testGetLanguage() {
+	public function testGetLanguage(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [],
 			'nl' => [],
@@ -731,7 +733,7 @@ class I18nDataTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals($this->referenceData['en'], $data->getLanguage('en'));
 	}
 
-	public function testGetReferenceLanguage() {
+	public function testGetReferenceLanguage(): void {
 		$rawData = array_merge($this->referenceData, [
 			'fr' => [],
 			'nl' => [],
diff --git a/tests/cli/i18n/I18nFileTest.php b/tests/cli/i18n/I18nFileTest.php
index 26566ddf1..662c14608 100644
--- a/tests/cli/i18n/I18nFileTest.php
+++ b/tests/cli/i18n/I18nFileTest.php
@@ -3,7 +3,7 @@
 require_once __DIR__ . '/../../../cli/i18n/I18nFile.php';
 
 class I18nFileTest extends PHPUnit\Framework\TestCase {
-	public function test() {
+	public function test(): void {
 		$before = $this->computeFilesHash();
 
 		$file = new I18nFile();
@@ -15,7 +15,8 @@ class I18nFileTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals($before, $after);
 	}
 
-	private function computeFilesHash() {
+	/** @return array<string,string> */
+	private function computeFilesHash(): array {
 		$hashes = [];
 
 		$dirs = new DirectoryIterator(I18N_PATH);
diff --git a/tests/cli/i18n/I18nUsageValidatorTest.php b/tests/cli/i18n/I18nUsageValidatorTest.php
index 531e77c5d..fdd75bf64 100644
--- a/tests/cli/i18n/I18nUsageValidatorTest.php
+++ b/tests/cli/i18n/I18nUsageValidatorTest.php
@@ -4,6 +4,7 @@ require_once __DIR__ . '/../../../cli/i18n/I18nValue.php';
 require_once __DIR__ . '/../../../cli/i18n/I18nUsageValidator.php';
 
 class I18nUsageValidatorTest extends PHPUnit\Framework\TestCase {
+	/** @var I18nValue */
 	private $value;
 
 	public function setUp(): void {
@@ -12,7 +13,7 @@ class I18nUsageValidatorTest extends PHPUnit\Framework\TestCase {
 			->getMock();
 	}
 
-	public function testDisplayReport() {
+	public function testDisplayReport(): void {
 		$validator = new I18nUsageValidator([], []);
 
 		$this->assertEquals("There is no data.\n", $validator->displayReport());
@@ -40,13 +41,13 @@ class I18nUsageValidatorTest extends PHPUnit\Framework\TestCase {
 		$validator->displayReport();
 	}
 
-	public function testValidateWhenNoData() {
+	public function testValidateWhenNoData(): void {
 		$validator = new I18nUsageValidator([], []);
 		$this->assertTrue($validator->validate());
 		$this->assertEquals('', $validator->displayResult());
 	}
 
-	public function testValidateWhenParentKeyExistsWithoutTransformation() {
+	public function testValidateWhenParentKeyExistsWithoutTransformation(): void {
 		$validator = new I18nUsageValidator([
 			'file1' => [
 				'file1.l1.l2._' => $this->value,
@@ -62,7 +63,7 @@ class I18nUsageValidatorTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals('', $validator->displayResult());
 	}
 
-	public function testValidateWhenParentKeyExistsWithTransformation() {
+	public function testValidateWhenParentKeyExistsWithTransformation(): void {
 		$validator = new I18nUsageValidator([
 			'file1' => [
 				'file1.l1.l2._' => $this->value,
@@ -78,7 +79,7 @@ class I18nUsageValidatorTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals('', $validator->displayResult());
 	}
 
-	public function testValidateWhenParentKeyDoesNotExist() {
+	public function testValidateWhenParentKeyDoesNotExist(): void {
 		$validator = new I18nUsageValidator([
 			'file1' => [
 				'file1.l1.l2._' => $this->value,
@@ -91,7 +92,7 @@ class I18nUsageValidatorTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals("Unused key file1.l1.l2._ - \nUnused key file2.l1.l2._ - \n", $validator->displayResult());
 	}
 
-	public function testValidateWhenChildKeyExists() {
+	public function testValidateWhenChildKeyExists(): void {
 		$validator = new I18nUsageValidator([
 			'file1' => [
 				'file1.l1.l2.k1' => $this->value,
@@ -107,7 +108,7 @@ class I18nUsageValidatorTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals('', $validator->displayResult());
 	}
 
-	public function testValidateWhenChildKeyDoesNotExist() {
+	public function testValidateWhenChildKeyDoesNotExist(): void {
 		$validator = new I18nUsageValidator([
 			'file1' => [
 				'file1.l1.l2.k1' => $this->value,
diff --git a/tests/cli/i18n/I18nValueTest.php b/tests/cli/i18n/I18nValueTest.php
index cabc8e072..7a1109a20 100644
--- a/tests/cli/i18n/I18nValueTest.php
+++ b/tests/cli/i18n/I18nValueTest.php
@@ -3,35 +3,35 @@
 require_once __DIR__ . '/../../../cli/i18n/I18nValue.php';
 
 class I18nValueTest extends PHPUnit\Framework\TestCase {
-	public function testConstructorWithoutState() {
+	public function testConstructorWithoutState(): void {
 		$value = new I18nValue('some value');
 		$this->assertEquals('some value', $value->getValue());
 		$this->assertFalse($value->isIgnore());
 		$this->assertFalse($value->isTodo());
 	}
 
-	public function testConstructorWithUnknownState() {
+	public function testConstructorWithUnknownState(): void {
 		$value = new I18nValue('some value -> unknown');
 		$this->assertEquals('some value', $value->getValue());
 		$this->assertFalse($value->isIgnore());
 		$this->assertFalse($value->isTodo());
 	}
 
-	public function testConstructorWithTodoState() {
+	public function testConstructorWithTodoState(): void {
 		$value = new I18nValue('some value -> todo');
 		$this->assertEquals('some value', $value->getValue());
 		$this->assertFalse($value->isIgnore());
 		$this->assertTrue($value->isTodo());
 	}
 
-	public function testConstructorWithIgnoreState() {
+	public function testConstructorWithIgnoreState(): void {
 		$value = new I18nValue('some value -> ignore');
 		$this->assertEquals('some value', $value->getValue());
 		$this->assertTrue($value->isIgnore());
 		$this->assertFalse($value->isTodo());
 	}
 
-	public function testClone() {
+	public function testClone(): void {
 		$value = new I18nValue('some value');
 		$clonedValue = clone $value;
 		$this->assertEquals('some value', $value->getValue());
@@ -42,21 +42,21 @@ class I18nValueTest extends PHPUnit\Framework\TestCase {
 		$this->assertTrue($clonedValue->isTodo());
 	}
 
-	public function testEqualWhenValueIsIdentical() {
+	public function testEqualWhenValueIsIdentical(): void {
 		$value = new I18nValue('some value');
 		$clonedValue = clone $value;
 		$this->assertTrue($value->equal($clonedValue));
 		$this->assertTrue($clonedValue->equal($value));
 	}
 
-	public function testEqualWhenValueIsDifferent() {
+	public function testEqualWhenValueIsDifferent(): void {
 		$value = new I18nValue('some value');
 		$otherValue = new I18nValue('some other value');
 		$this->assertFalse($value->equal($otherValue));
 		$this->assertFalse($otherValue->equal($value));
 	}
 
-	public function testStates() {
+	public function testStates(): void {
 		$reflectionProperty = new ReflectionProperty(I18nValue::class, 'state');
 		$reflectionProperty->setAccessible(true);
 
@@ -74,7 +74,7 @@ class I18nValueTest extends PHPUnit\Framework\TestCase {
 		$this->assertEquals('todo', $reflectionProperty->getValue($value));
 	}
 
-	public function testToString() {
+	public function testToString(): void {
 		$value = new I18nValue('some value');
 		$this->assertEquals('some value', $value->__toString());
 		$value->markAsTodo();