diff --git a/src/Samsara/Newton/Units/Core/Constant.php b/src/Samsara/Newton/Units/Core/ConstantQuantity.php
similarity index 100%
rename from src/Samsara/Newton/Units/Core/Constant.php
rename to src/Samsara/Newton/Units/Core/ConstantQuantity.php
diff --git a/tests/Samsara/Newton/Units/ConstantsTest.php b/tests/Samsara/Newton/Units/ConstantsTest.php
new file mode 100644
index 0000000..89be954
--- /dev/null
+++ b/tests/Samsara/Newton/Units/ConstantsTest.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace Samsara\Newton\Units\PhysicsConstants;
+
+class ConstantsTest extends \PHPUnit_Framework_TestCase
+{
+
+    public function testGravitation()
+    {
+        $gravitation = new Gravitation();
+
+        $this->assertInstanceOf(
+            'Samsara\\Newton\\Units\\PhysicsConstants\\Gravitation',
+            $gravitation
+        );
+
+        $this->assertEquals(
+            '0.0000000000667384',
+            $gravitation->getValue()
+        );
+
+        $gravitation->preConvertedAdd(1);
+        $gravitation->preConvertedMultiply(2);
+        $gravitation->preConvertedDivide(10);
+        $gravitation->preConvertedSubtract(1);
+        $gravitation->add($gravitation);
+        $gravitation->add($gravitation);
+        $gravitation->subtract($gravitation);
+
+        $this->assertEquals(
+            '0.0000000000667384',
+            $gravitation->getValue()
+        );
+
+        $this->assertEquals(
+            'N (m/kg)^2',
+            $gravitation->getUnit()
+        );
+    }
+
+}
\ No newline at end of file