diff --git a/tests/unit/JSONDataFormatterTest.php b/tests/unit/JSONDataFormatterTest.php
index 2016479..b66cad6 100644
--- a/tests/unit/JSONDataFormatterTest.php
+++ b/tests/unit/JSONDataFormatterTest.php
@@ -31,8 +31,29 @@ class JSONDataFormatterTest extends SapphireTest
 
         // Grab test object
         $formatter = new JSONDataFormatter();
-        $parent = $this->objFromFixture(JSONDataFormatterTypeTestObject::class, 'original');
-        $json = json_decode($formatter->convertDataObject($parent));
+
+        $parent = $this->objFromFixture(JSONDataFormatterTypeTestObject::class, 'parent');
+        $json = $formatter->convertDataObject($parent);
+
+        $this->assertRegexp('/"ID":\d+/', $json, 'PK casted to integer');
+        $this->assertRegexp('/"Created":"\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}"/', $json, 'Datetime casted to string');
+        $this->assertContains('"Name":"Parent"', $json, 'String casted to string');
+        $this->assertContains('"Active":true', $json, 'Boolean casted to boolean');
+        $this->assertContains('"Sort":17', $json, 'Integer casted to integer');
+        $this->assertContains('"Average":1.2345', $json, 'Float casted to float');
+        $this->assertContains('"ParentID":0', $json, 'Empty FK is 0');
+
+        $child3 = $this->objFromFixture(JSONDataFormatterTypeTestObject::class, 'child3');
+        $json = $formatter->convertDataObject($child3);
+
+        $this->assertContains('"Name":null', $json, 'Empty string is null');
+        $this->assertContains('"Active":false', $json, 'Empty boolean is false');
+        $this->assertContains('"Sort":0', $json, 'Empty integer is 0');
+        $this->assertContains('"Average":0', $json, 'Empty float is 0');
+        $this->assertRegexp('/"ParentID":\d+/', $json, 'FK casted to integer');
+
+        $original = $this->objFromFixture(JSONDataFormatterTypeTestObject::class, 'original');
+        $json = json_decode($formatter->convertDataObject($original));
 
         // Returns valid array and isn't null
         $this->assertNotEmpty($json, 'Array is empty');