Functionally test enforcing Throwable as rejection

tests/FunctionalRejectTest.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace React\Promise;
+
+use stdClass;
+
+class FunctionalRejectTest extends TestCase
+{
+    public function nonThrowables()
+    {
+        yield '1' => [1];
+        yield 'true' => [true];
+        yield 'stdClass' => [new stdClass()];
+    }
+
+    /**
+     * @test
+     * @expectedException \TypeError
+     * @dataProvider nonThrowables
+     */
+    public function shouldThrowWhenCalledWithANonException($input)
+    {
+        all([
+            resolve(true),
+            race([
+                (new Promise(function ($_, $reject) use ($input) {
+                    $reject($input);
+                })),
+                (new Promise(function () {
+                })),
+            ])
+        ])->done($this->expectCallableNever());
+    }
+}