Guard against precision issues on time fractions

test/functional/TimeFractionPrecisionTest.php

@@ -0,0 +1,61 @@
+<?php
+declare(strict_types=1);
+
+namespace Lcobucci\JWT\FunctionalTests;
+
+use DateTimeImmutable;
+use Lcobucci\JWT\Configuration;
+use Lcobucci\JWT\Token\Plain;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \Lcobucci\JWT\Configuration
+ * @covers \Lcobucci\JWT\Encoding\JoseEncoder
+ * @covers \Lcobucci\JWT\Encoding\ChainedFormatter
+ * @covers \Lcobucci\JWT\Encoding\MicrosecondBasedDateConversion
+ * @covers \Lcobucci\JWT\Encoding\UnifyAudience
+ * @covers \Lcobucci\JWT\Token\Builder
+ * @covers \Lcobucci\JWT\Token\Parser
+ * @covers \Lcobucci\JWT\Token\Plain
+ * @covers \Lcobucci\JWT\Token\DataSet
+ * @covers \Lcobucci\JWT\Token\Signature
+ * @covers \Lcobucci\JWT\Signer\Key\InMemory
+ * @covers \Lcobucci\JWT\Signer\None
+ * @covers \Lcobucci\JWT\Validation\Validator
+ * @covers \Lcobucci\JWT\Validation\RequiredConstraintsViolated
+ * @covers \Lcobucci\JWT\Validation\Constraint\SignedWith
+ */
+final class TimeFractionPrecisionTest extends TestCase
+{
+    /**
+     * @test
+     * @dataProvider datesWithPotentialRoundingIssues
+     */
+    public function timeFractionsPrecisionsAreRespected(string $timeFraction): void
+    {
+        $config = Configuration::forUnsecuredSigner();
+
+        $issuedAt = DateTimeImmutable::createFromFormat('U.u', $timeFraction);
+
+        self::assertInstanceOf(DateTimeImmutable::class, $issuedAt);
+        self::assertSame($timeFraction, $issuedAt->format('U.u'));
+
+        $token = $config->builder()
+            ->issuedAt($issuedAt)
+            ->getToken($config->signer(), $config->signingKey());
+
+        $parsedToken = $config->parser()->parse($token->toString());
+
+        self::assertInstanceOf(Plain::class, $parsedToken);
+        self::assertSame($timeFraction, $parsedToken->claims()->get('iat')->format('U.u'));
+    }
+
+    /** @return iterable<string[]> */
+    public function datesWithPotentialRoundingIssues(): iterable
+    {
+        yield ['1613938511.017448'];
+        yield ['1613938511.023691'];
+        yield ['1613938511.018045'];
+        yield ['1616074725.008455'];
+    }
+}