diff --git a/pom.xml b/pom.xml
index 07e197a..0d42963 100644
--- a/pom.xml
+++ b/pom.xml
@@ -99,6 +99,11 @@
             <version>4.12</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>2.1.0-RC.1</version>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/src/test/java/org/graylog2/syslog4j/impl/message/processor/AbstractSyslogMessageProcessorTest.java b/src/test/java/org/graylog2/syslog4j/impl/message/processor/AbstractSyslogMessageProcessorTest.java
new file mode 100644
index 0000000..4a3b3b7
--- /dev/null
+++ b/src/test/java/org/graylog2/syslog4j/impl/message/processor/AbstractSyslogMessageProcessorTest.java
@@ -0,0 +1,49 @@
+package org.graylog2.syslog4j.impl.message.processor;
+
+import org.graylog2.syslog4j.SyslogConstants;
+import org.junit.Test;
+
+import java.util.Date;
+
+import static org.junit.Assert.assertEquals;
+
+public class AbstractSyslogMessageProcessorTest {
+    @Test
+    public void appendPriority() throws Exception {
+        final AbstractSyslogMessageProcessor messageProcessor = new AbstractSyslogMessageProcessor() {
+            @Override
+            protected void appendTimestamp(StringBuffer buffer, Date datetime) {
+            }
+
+            @Override
+            public String createSyslogHeader(int facility, int level, String localName, boolean sendLocalTimestamp, boolean sendLocalName) {
+                return null;
+            }
+
+            @Override
+            public String createSyslogHeader(int facility, int level, String localName, boolean sendLocalName, Date datetime) {
+                return null;
+            }
+        };
+
+        // For example, a kernel message (Facility=0) with a Severity of Emergency (Severity=0)
+        // would have a Priority value of 0.
+        // -- https://tools.ietf.org/html/rfc5424#section-6.2.1
+        final StringBuffer sb1 = new StringBuffer();
+        messageProcessor.appendPriority(sb1, SyslogConstants.FACILITY_KERN, SyslogConstants.LEVEL_EMERGENCY);
+        assertEquals("<0>", sb1.toString());
+
+        // Also, a "local use 4" message (Facility=20) with a Severity of Notice (Severity=5)
+        // would have a Priority value of 165.
+        // -- https://tools.ietf.org/html/rfc5424#section-6.2.1
+        final StringBuffer sb2 = new StringBuffer();
+        messageProcessor.appendPriority(sb2, SyslogConstants.FACILITY_LOCAL4, SyslogConstants.LEVEL_NOTICE);
+        assertEquals("<165>", sb2.toString());
+
+        // Upper bound: Facility = 23 (local7), Level = 7 (Debug)
+        final StringBuffer sb3 = new StringBuffer();
+        messageProcessor.appendPriority(sb3, SyslogConstants.FACILITY_LOCAL7, SyslogConstants.LEVEL_DEBUG);
+        assertEquals("<191>", sb3.toString());
+    }
+
+}
\ No newline at end of file
diff --git a/src/test/java/org/graylog2/syslog4j/impl/unix/UnixSyslogTest.java b/src/test/java/org/graylog2/syslog4j/impl/unix/UnixSyslogTest.java
new file mode 100644
index 0000000..f849d88
--- /dev/null
+++ b/src/test/java/org/graylog2/syslog4j/impl/unix/UnixSyslogTest.java
@@ -0,0 +1,25 @@
+package org.graylog2.syslog4j.impl.unix;
+
+import org.graylog2.syslog4j.SyslogConstants;
+import org.junit.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+public class UnixSyslogTest {
+    @Test
+    public void writeUsesCorrectSyslogPriority() throws Exception {
+        final UnixSyslog.CLibrary mockLibrary = mock(UnixSyslog.CLibrary.class);
+        UnixSyslog.libraryInstance = mockLibrary;
+        UnixSyslog.currentFacility = SyslogConstants.FACILITY_LOCAL4;
+
+        final UnixSyslogConfig config = new UnixSyslogConfig();
+        config.setFacility(SyslogConstants.FACILITY_LOCAL4);
+
+        UnixSyslog.write(SyslogConstants.LEVEL_NOTICE, "Test", config);
+
+        verify(mockLibrary, times(1)).syslog(165, "%s", "Test");
+    }
+
+}
\ No newline at end of file