diff --git a/tests/Validator/ConfigurationValidatorTest.php b/tests/Validator/ConfigurationValidatorTest.php
index 4885b84..ca34691 100644
--- a/tests/Validator/ConfigurationValidatorTest.php
+++ b/tests/Validator/ConfigurationValidatorTest.php
@@ -21,3 +21,20 @@ test('The project name should be a string', function (mixed $projectName, int $e
     yield 'True' => [true, 1];
     yield 'False' => [false, 2];
 });
+
+test('The project language should be a supported language', function (mixed $language, int $expectedViolationCount) {
+    $configuration = [
+        'language' => $language,
+    ];
+
+    expect($this->validator->validate($configuration))
+        ->toHaveCount($expectedViolationCount);
+})->with(function () {
+    yield 'Supported language string' => ['php', 0];
+    yield 'Non-supported language string' => ['not-supported', 1];
+    yield 'Empty string' => ['', 1];
+    yield 'Integer' => [1, 2];
+    yield 'Null' => [null, 1];
+    yield 'True' => [true, 2];
+    yield 'False' => [false, 2];
+});