feat: adds toHaveKeys expectation

tests/.snapshots/success.txt

@@ -180,6 +180,11 @@
    PASS  Tests\Expect\toHaveKey
   ✓ pass
   ✓ failures
+  ✓ not failures
+
+   PASS  Tests\Expect\toHaveKeys
+  ✓ pass
+  ✓ failures
   ✓ not failures
 
    PASS  Tests\Expect\toHaveProperty
@@ -353,5 +358,5 @@
   ✓ depends with defined arguments
   ✓ depends run test only once
 
-  Tests:  6 skipped, 208 passed
+  Tests:  6 skipped, 211 passed
   

tests/Expect/toHaveKeys.php

@@ -0,0 +1,15 @@
+<?php
+
+use PHPUnit\Framework\ExpectationFailedException;
+
+test('pass', function () {
+    expect(['a' => 1, 'b', 'c' => 'world'])->toHaveKeys(['a', 'c']);
+});
+
+test('failures', function () {
+    expect(['a' => 1, 'b', 'c' => 'world'])->toHaveKeys(['a', 'd']);
+})->throws(ExpectationFailedException::class);
+
+test('not failures', function () {
+    expect(['a' => 1, 'hello' => 'world', 'c'])->not->toHaveKeys(['hello', 'c']);
+})->throws(ExpectationFailedException::class);