IOUtils.byteArray NoSuchMethodError in Eclipse

Question

I am running a unit test in an Eclipse project, and when I run the following JUnit test

@Before
public void setup() {
    final byte[] array = IOUtils.byteArray();
    ...
}

I get the following error:

java.lang.NoSuchMethodError: org.apache.commons.io.IOUtils.byteArray()[B

I have included Apache commons-io 2.11.0 in my classpath:

<?xml version="1.0" encoding="UTF-8"?>
<classpath>
... 
    <classpathentry kind="var" path="APACHE_IO/commons-io-2.11.0/commons-io-2.11.0.jar"/>
... 
</classpath>

What am I missing here?