1 files changed, 67 insertions, 0 deletions
diff --git a/tests/TimestampTest.php b/tests/TimestampTest.php
new file mode 100644
index 0000000..d157adf
--- /dev/null
+++ b/tests/TimestampTest.php
@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Zhineng\Snowflake\Tests;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\TestCase;
+use Zhineng\Snowflake\Timestamp;
+
+#[CoversClass(Timestamp::class)]
+final class TimestampTest extends TestCase
+{
+    public function testTimestampCanBeInitialized(): void
+    {
+        $field = new Timestamp('timestamp', 41);
+        $this->assertSame('timestamp', $field->name);
+        $this->assertSame(41, $field->bits);
+    }
+
+    public function testTimestampHasDefaultParameterValues(): void
+    {
+        $field = new Timestamp;
+        $this->assertSame('timestamp', $field->name);
+        $this->assertSame(41, $field->bits);
+    }
+
+    public function testTimestampHasMakeFactoryMethod(): void
+    {
+        $field = Timestamp::make('timestamp', 41);
+        $this->assertSame('timestamp', $field->name);
+        $this->assertSame(41, $field->bits);
+    }
+
+    public function testTimestampHasDynamicValue(): void
+    {
+        $field = new Timestamp;
+        $value1 = $field->value();
+        usleep(1000); // Sleep for 1 millisecond
+        $value2 = $field->value();
+        $this->assertGreaterThan($value1, $value2);
+    }
+
+    public function testEpochCanBeCustomized(): void
+    {
+        $epoch = new \DateTime('2026-01-01 00:00:00');
+        $field = new Timestamp('timestamp', 41, $epoch);
+        $now = (int) floor(microtime(as_float: true) * 1000);
+        $this->assertSame($now - $epoch->getTimestamp() * 1000, $field->value());
+    }
+
+    public function testEpochCanBeSetAsInteger(): void
+    {
+        $epoch = new \DateTime('2026-01-01 00:00:00');
+        $timestampInMillis = $epoch->getTimestamp() * 1000;
+        $field = new Timestamp('timestamp', 41, $timestampInMillis);
+        $now = (int) floor(microtime(as_float: true) * 1000);
+        $this->assertSame($now - $timestampInMillis, $field->value());
+    }
+
+    public function testEpochMustBeNonNegative(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Epoch must be non-negative.');
+        new Timestamp('timestamp', 41, -1);
+    }
+}