diff --git a/build.gradle b/build.gradle
index 020c1756b4c385a85a4c1c9916e79b658edb6775..149926618f6de1bf2d5774cf5ea3b874ddc3726f 100644
--- a/build.gradle
+++ b/build.gradle
@@ -21,6 +21,7 @@ buildscript {
 dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.4.0'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.4.0'
+    testCompile 'org.assertj:assertj-core:3.12.1'
     compile 'com.fasterxml.jackson.core:jackson-core:2.9.8'
     compile 'com.fasterxml.jackson.core:jackson-databind:2.9.8'
     runtime 'org.jastadd:jastadd:2.3.2'
diff --git a/src/test/java/org/jastadd/relast/tests/Serializer.java b/src/test/java/org/jastadd/relast/tests/Serializer.java
index 5bfa84f5f51481f87dc5a81e060a7d51fdbc9545..3289ef26151053e947fd3ce4338a6984318c9f4d 100644
--- a/src/test/java/org/jastadd/relast/tests/Serializer.java
+++ b/src/test/java/org/jastadd/relast/tests/Serializer.java
@@ -4,6 +4,9 @@ import org.junit.jupiter.api.Test;
 import serializer.ast.*;
 
 import java.io.File;
+import java.io.IOException;
+
+import static org.assertj.core.api.Assertions.assertThat;
 
 
 @SuppressWarnings("ArraysAsListWithZeroOrOneArgument")
@@ -11,7 +14,7 @@ class Serializer {
 
 
   @Test
-  void testDi1() throws SerializationException, DeserializationException {
+  void testDi1() throws SerializationException, DeserializationException, IOException {
 
     Root r = new Root();
     A a1 = new A("a1");
@@ -87,12 +90,16 @@ class Serializer {
     a1.addBi9(b2);
     a2.addBi9(b2);
 
-    File f = new File("test.json");
+    File f = File.createTempFile("original", ".json");
+    System.out.println(f.getAbsoluteFile());
     r.serialize(f);
 
     Root copy = Root.deserialize(f);
-    File f2 = new File("copy.json");
+    File f2 = File.createTempFile("copy", ".json");
     copy.serialize(f2);
+
+    assertThat(f2).hasSameContentAs(f);
+
   }
 
 }