diff --git a/java_gen/pre-written/src/test/java/org/projectfloodlight/protocol/OFOxmTest.java b/java_gen/pre-written/src/test/java/org/projectfloodlight/protocol/OFOxmTest.java
new file mode 100644
index 0000000..8482886
--- /dev/null
+++ b/java_gen/pre-written/src/test/java/org/projectfloodlight/protocol/OFOxmTest.java
@@ -0,0 +1,62 @@
+package org.projectfloodlight.protocol;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+import org.hamcrest.CoreMatchers;
+import org.junit.Before;
+import org.junit.Test;
+import org.projectfloodlight.openflow.protocol.OFFactories;
+import org.projectfloodlight.openflow.protocol.OFVersion;
+import org.projectfloodlight.openflow.protocol.oxm.OFOxm;
+import org.projectfloodlight.openflow.protocol.oxm.OFOxmIpv4Src;
+import org.projectfloodlight.openflow.protocol.oxm.OFOxmIpv4SrcMasked;
+import org.projectfloodlight.openflow.protocol.oxm.OFOxms;
+import org.projectfloodlight.openflow.types.IPv4Address;
+import org.projectfloodlight.openflow.types.IPv4AddressWithMask;
+
+public class OFOxmTest {
+    private OFOxms oxms;
+
+    @Before
+    public void setup() {
+        oxms = OFFactories.getFactory(OFVersion.OF_13).oxms();
+    }
+
+    @Test
+    public void testGetCanonicalFullMask() {
+        IPv4AddressWithMask empty = IPv4AddressWithMask.of("0.0.0.0/0");
+        assertEquals(IPv4Address.FULL_MASK, empty.getMask());
+        OFOxmIpv4SrcMasked ipv4SrcMasked = oxms.ipv4SrcMasked(empty.getValue(), empty.getMask());
+        // canonicalize should remove /0
+        assertNull(ipv4SrcMasked.getCanonical());
+    }
+
+    @Test
+    public void testGetCanonicalNoMask() {
+        IPv4AddressWithMask fullIp = IPv4AddressWithMask.of("1.2.3.4/32");
+        assertEquals(IPv4Address.NO_MASK, fullIp.getMask());
+        OFOxmIpv4SrcMasked ipv4SrcMasked = oxms.ipv4SrcMasked(fullIp.getValue(), fullIp.getMask());
+        assertTrue(ipv4SrcMasked.isMasked());
+        assertEquals(IPv4Address.NO_MASK, ipv4SrcMasked.getMask());
+
+        // canonicalize should convert the masked oxm to the non-masked one
+        OFOxm<IPv4Address> canonical = ipv4SrcMasked.getCanonical();
+        assertThat(canonical, CoreMatchers.instanceOf(OFOxmIpv4Src.class));
+        assertFalse(canonical.isMasked());
+    }
+
+    @Test
+    public void testGetCanonicalNormalMask() {
+        IPv4AddressWithMask ip = IPv4AddressWithMask.of("1.2.3.0/24");
+        OFOxmIpv4SrcMasked ipv4SrcMasked = oxms.ipv4SrcMasked(ip.getValue(), ip.getMask());
+        assertTrue(ipv4SrcMasked.isMasked());
+
+        // canonicalize should convert the masked oxm to the non-masked one
+        OFOxm<IPv4Address> canonical = ipv4SrcMasked.getCanonical();
+        assertEquals(ipv4SrcMasked, canonical);
+    }
+}