add to be backed enum expectation

tests/Features/Expect/toBeIntBackedEnum.php

@@ -0,0 +1,9 @@
+<?php
+
+test('enum is backed by int')
+    ->expect('Tests\Fixtures\Arch\ToBeIntBackedEnum\HasIntBacking')
+    ->toBeIntBackedEnum();
+
+test('enum is not backed by int')
+    ->expect('Tests\Fixtures\Arch\ToBeIntBackedEnum\HasStringBacking')
+    ->not->toBeIntBackedEnum();

tests/Features/Expect/toBeStringBackedEnum.php

@@ -0,0 +1,9 @@
+<?php
+
+test('enum is backed by string')
+    ->expect('Tests\Fixtures\Arch\ToBeStringBackedEnum\HasStringBacking')
+    ->toBeStringBackedEnum();
+
+test('enum is not backed by string')
+    ->expect('Tests\Fixtures\Arch\ToBeStringBackedEnum\HasIntBacking')
+    ->not->toBeStringBackedEnum();

tests/Fixtures/Arch/ToBeIntBackedEnum/HasIntBacking/HasIntBackingEnum.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Fixtures\Arch\ToBeIntBackedEnum\HasIntBacking;
+
+enum HasIntBackingEnum: int
+{
+    case IntBacked = 1;
+}

tests/Fixtures/Arch/ToBeIntBackedEnum/HasStringBacking/HasStringBackingEnum.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Fixtures\Arch\ToBeIntBackedEnum\HasStringBacking;
+
+enum HasStringBackingEnum: string
+{
+    case StringBacked = 'Testing';
+}

tests/Fixtures/Arch/ToBeStringBackedEnum/HasIntBacking/HasIntBackingEnum.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Fixtures\Arch\ToBeStringBackedEnum\HasIntBacking;
+
+enum HasIntBackingEnum: int
+{
+    case IntBacked = 1;
+}

tests/Fixtures/Arch/ToBeStringBackedEnum/HasStringBacking/HasStringBackingEnum.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Fixtures\Arch\ToBeStringBackedEnum\HasStringBacking;
+
+enum HasStringBackingEnum: string
+{
+    case StringBacked = 'Testing';
+}