feat: add toHaveSnakeCaseKeys

tests/Features/Expect/toHaveSnakeCaseKeys.php

@@ -0,0 +1,31 @@
+<?php
+
+use Pest\Exceptions\InvalidExpectationValue;
+use PHPUnit\Framework\ExpectationFailedException;
+
+$array = [
+    'snake' => true,
+    'snake_case' => [
+        'snake' => true,
+        'snake_case' => [
+            'snake' => true,
+            'snake_case' => true,
+        ],
+    ],
+];
+
+test('pass', function () use ($array) {
+    expect($array)->toHaveSnakeCaseKeys();
+});
+
+test('failures', function () {
+    expect('not-an-array')->toHaveSnakeCaseKeys();
+})->throws(InvalidExpectationValue::class);
+
+test('failures with message', function () use ($array) {
+    expect($array)->not->toHaveSnakeCaseKeys('oh no!');
+})->throws(ExpectationFailedException::class, 'oh no!');
+
+test('not failures', function () use ($array) {
+    expect($array)->not->toHaveSnakeCaseKeys();
+})->throws(ExpectationFailedException::class);