diff --git a/composer.json b/composer.json
index e182008..a3c97ed 100644
--- a/composer.json
+++ b/composer.json
@@ -9,7 +9,8 @@
             "email": "oliver@oliverdavies.uk"
         }
     ],
-    "require": {},
+    "require": {
+    },
     "require-dev": {
         "phpunit/phpunit": "^5.7"
     },
diff --git a/src/Filter.php b/src/Filter.php
new file mode 100644
index 0000000..fef13d8
--- /dev/null
+++ b/src/Filter.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace Opdavies\GmailFilterBuilder;
+
+class Filter
+{
+    public function has($value)
+    {
+        return ['hasTheWord' => $value];
+    }
+
+    public function from()
+    {
+        return ['from' =>  func_get_args()];
+    }
+
+    public function label($label)
+    {
+        return ['label' => $label];
+    }
+
+    public function archive()
+    {
+        return ['shouldArchive' => 'true'];
+    }
+
+    public function labelAndArchive($label)
+    {
+        return $this->label($label) + $this->archive();
+    }
+
+    public function spam()
+    {
+        return [
+            'shouldSpam' => 'true',
+            'shouldNeverSpam' => 'false',
+        ];
+    }
+
+    public function neverSpam()
+    {
+        return [
+            'shouldSpam' => 'false',
+            'shouldNeverSpam' => 'true',
+        ];
+    }
+
+    public function trash()
+    {
+        return ['shouldTrash' => 'true'];
+    }
+}
diff --git a/tests/Unit/FilterTest.php b/tests/Unit/FilterTest.php
new file mode 100644
index 0000000..c67f892
--- /dev/null
+++ b/tests/Unit/FilterTest.php
@@ -0,0 +1,121 @@
+<?php
+
+namespace Opdavies\Tests\GmailFilterBuilder;
+
+use Opdavies\GmailFilterBuilder\Filter;
+
+class FilterTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @var Filter
+     */
+    private $filter;
+
+    /**
+     * {@inheritdoc}
+     */
+    public function setUp()
+    {
+        parent::setUp();
+
+        $this->filter = new Filter();
+    }
+
+    /**
+     * @covers Filter::has()
+     */
+    public function testHas()
+    {
+        $this->assertEquals(
+            ['hasTheWord' => 'something'],
+            $this->filter->has('something')
+        );
+    }
+
+    /**
+     * @covers Filter::from()
+     */
+    public function testFrom()
+    {
+        // Ensure that we can set one from address.
+        $this->assertEquals(
+            ['from' => ['foo@example.com']],
+            $this->filter->from('foo@example.com')
+        );
+
+        // Ensure that we can set multiple from addresses.
+        $this->assertEquals(
+            ['from' => ['foo@example.com', 'bar@example.com']],
+            $this->filter->from('foo@example.com', 'bar@example.com')
+        );
+    }
+
+    /**
+     * @covers Filter::label()
+     */
+    public function testLabel()
+    {
+        $this->assertEquals(['label' => 'Foo'], $this->filter->label('Foo'));
+    }
+
+    /**
+     * @covers Filter::archive()
+     */
+    public function testArchive()
+    {
+        $this->assertEquals(
+            ['shouldArchive' => 'true'],
+            $this->filter->archive()
+        );
+    }
+
+    /**
+     * @covers Filter::labelAndArchive()
+     */
+    public function testLabelAndArchive()
+    {
+        $this->assertEquals(
+            ['shouldArchive' => 'true', 'label' => 'Foo'],
+            $this->filter->labelAndArchive('Foo')
+        );
+    }
+
+    /**
+     * @covers Filter::spam()
+     */
+    public function testSpam()
+    {
+        $this->assertEquals(
+            [
+                'shouldSpam' => 'true',
+                'shouldNeverSpam' => 'false'
+            ],
+            $this->filter->spam()
+        );
+    }
+
+    /**
+     * @covers Filter::neverSpam()
+     */
+    public function testNeverSpam()
+    {
+        $this->assertEquals(
+            [
+                'shouldSpam' => 'false',
+                'shouldNeverSpam' => 'true'
+            ],
+            $this->filter->neverSpam()
+        );
+    }
+
+    /**
+     * @covers Filter::trash()
+     */
+    public function testTrash()
+    {
+        $this->assertEquals(
+            ['shouldTrash' => 'true'],
+            $this->filter->trash()
+        );
+    }
+}