Add toBeIn expectation

src/Expectation.php

@@ -371,6 +371,18 @@ public function toEqualWithDelta($expected, float $delta): Expectation
         return $this;
     }
 
+    /**
+     * Asserts that the value is one of the given values.
+     *
+     * @param iterable<int|string, mixed> $values
+     */
+    public function toBeIn(iterable $values): Expectation
+    {
+        Assert::assertContains($this->value, $values);
+
+        return $this;
+    }
+
     /**
      * Asserts that the value is infinite.
      */

tests/Features/Expect/toBeIn.php

@@ -0,0 +1,16 @@
+<?php
+
+use PHPUnit\Framework\ExpectationFailedException;
+
+test('passes', function () {
+    expect('a')->toBeIn(['a', 'b', 'c']);
+    expect('d')->not->toBeIn(['a', 'b', 'c']);
+});
+
+test('failures', function () {
+    expect('d')->toBeIn(['a', 'b', 'c']);
+})->throws(ExpectationFailedException::class);
+
+test('not failures', function () {
+    expect('a')->not->toBeIn(['a', 'b', 'c']);
+})->throws(ExpectationFailedException::class);