I have set up the 'build chain' target so that the coverage files (*.em, *.ec) from the unit and integration targets are available to it.
I created an ant build file specifically for the build chain target (with help from the emma doco!):
<project name="coverage-merge" basedir="." default="all">
<!-- directory that contains emma.jar and emma_ant.jar: -->
<property name="emma.dir" value="${basedir}/lib"/>
<property name="coverage.dir" location="${basedir}/coverage"/>
<path id="emma.lib">
<pathelement location="${emma.dir}/emma-teamcity-3.1.1.jar"/>
<pathelement location="${emma.dir}/emma_ant-2.0.5312.jar"/>
</path>
<taskdef resource="emma_ant.properties" classpathref="emma.lib"/>
<target name="all" depends="-report"/>
<target name="-report">
<emma>
<report sourcepath="${src.dir}" sort="+block,+name,+method,+class"
metrics="method:70,block:80,line:80,class:100">
<infileset dir="${coverage.dir}" includes="**/*.em, **/*.ec"/>
<!-- for every type of report desired, configure a nested
element; various report parameters
can be inherited from the parent <report>
and individually overridden for each report type:
-->
<txt outfile="${coverage.dir}/coverage.txt" depth="package"
columns="class,method,block,line,name"/>
<xml outfile="${coverage.dir}/coverage.xml" depth="package"/>
<html outfile="${coverage.dir}/coverage.html" depth="method"
columns="name,class,method,block,line"/>
</report>
</emma>
</target>
</project>
...which merges all the coverage files into a single report!
The metrics parameter of report sets the highlight threshold for the html report, so that the percentages against packages and files that are lower than the threshold are highlighted in red.
Modifying the xml output will allow me to use something like andariel to run an xpath over the results, and then force the build to fail if thresholds are not met!