Add tests

tests/Clock/FrozenClockTest.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DigitalCraftsman\DateTimePrecision\Clock;
+
+use DigitalCraftsman\DateTimePrecision\Moment;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(FrozenClock::class)]
+final class FrozenClockTest extends TestCase
+{
+    #[Test]
+    public function freeze_works(): void
+    {
+        // -- Arrange
+        $clock = new FrozenClock();
+        $moment = Moment::fromStringInTimeZone('2024-05-06 08:00:00', new \DateTimeZone('Europe/Berlin'));
+
+        // -- Act
+        $clock->freeze($moment);
+
+        // -- Assert
+        self::assertSame($moment, $clock->now());
+    }
+}

tests/Clock/SystemClockTest.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DigitalCraftsman\DateTimePrecision\Clock;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Only very little that's possible to test here, so we do what's possible.
+ */
+#[CoversClass(SystemClock::class)]
+final class SystemClockTest extends TestCase
+{
+    #[Test]
+    public function now_works(): void
+    {
+        // -- Arrange
+        $clock = new SystemClock();
+
+        // -- Act
+        $moment = $clock->now();
+
+        // -- Assert
+        self::assertEquals($moment->dateTime->getTimezone(), new \DateTimeZone('UTC'));
+    }
+}