diff --git a/src/Context.php b/src/Context.php
index fda96c9..7b9b297 100644
--- a/src/Context.php
+++ b/src/Context.php
@@ -35,6 +35,11 @@ public function set(string $key, mixed $value): void
         $this->context[$key] = $value;
     }
 
+    public function remove(string $key): void
+    {
+        unset($this->context[$key]);
+    }
+
     public function offsetExists($offset): bool
     {
         return $this->has($offset);
@@ -56,7 +61,7 @@ public function offsetSet($offset, $value): void
 
     public function offsetUnset($offset): void
     {
-        unset($this->context[$offset]);
+        $this->remove($offset);
     }
 
     public function getIterator(): \ArrayIterator
diff --git a/tests/ContextTest.php b/tests/ContextTest.php
new file mode 100644
index 0000000..96b5d66
--- /dev/null
+++ b/tests/ContextTest.php
@@ -0,0 +1,130 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Setono\CronBuilder;
+
+use PHPUnit\Framework\TestCase;
+
+final class ContextTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function it_sets(): void
+    {
+        $context = new Context();
+        $context->set('env', 'prod');
+
+        self::assertSame('prod', $context->get('env'));
+    }
+
+    /**
+     * @test
+     */
+    public function it_removes(): void
+    {
+        $context = new Context();
+        $context->set('env', 'prod');
+        $context->remove('env');
+
+        self::assertNull($context->get('env'));
+    }
+
+    /**
+     * @test
+     */
+    public function it_has(): void
+    {
+        $context = new Context();
+        $context->set('env', 'prod');
+
+        self::assertTrue($context->has('env'));
+        self::assertFalse($context->has('foo'));
+    }
+
+    /**
+     * @test
+     */
+    public function it_gets_default(): void
+    {
+        $context = new Context();
+        self::assertNull($context->get('env'));
+        self::assertSame('default', $context->get('env', 'default'));
+    }
+
+    /**
+     * @test
+     */
+    public function it_iterates(): void
+    {
+        $context = new Context(['env' => 'prod', 'foo' => 'bar']);
+        $values = [];
+
+        /** @var mixed $value */
+        foreach ($context as $key => $value) {
+            /** @psalm-suppress MixedAssignment */
+            $values[$key] = $value;
+        }
+
+        self::assertSame(['env' => 'prod', 'foo' => 'bar'], $values);
+    }
+
+    /**
+     * @test
+     */
+    public function it_counts(): void
+    {
+        $context = new Context(['env' => 'prod', 'foo' => 'bar']);
+        self::assertCount(2, $context);
+    }
+
+    /**
+     * @test
+     */
+    public function it_offset_exists(): void
+    {
+        $context = new Context(['env' => 'prod', 'foo' => 'bar']);
+        self::assertTrue(isset($context['env']));
+        self::assertFalse(isset($context['baz']));
+    }
+
+    /**
+     * @test
+     */
+    public function it_offset_get(): void
+    {
+        $context = new Context(['env' => 'prod', 'foo' => 'bar']);
+        self::assertSame('prod', $context['env']);
+    }
+
+    /**
+     * @test
+     */
+    public function it_offset_set(): void
+    {
+        $context = new Context();
+        $context['env'] = 'prod';
+        self::assertSame('prod', $context['env']);
+    }
+
+    /**
+     * @test
+     */
+    public function it_offset_unset(): void
+    {
+        $context = new Context(['env' => 'prod', 'foo' => 'bar']);
+        unset($context['env']);
+        self::assertNull($context['env']);
+    }
+
+    /**
+     * @test
+     */
+    public function it_throws_exception_on_null_offset(): void
+    {
+        $context = new Context();
+        $this->expectException(\InvalidArgumentException::class);
+        $context[] = 'foo';
+    }
+}