add rudimentary testcase for <cab> task

src/tests/antunit/taskdefs/optional/cab.xml

@@ -0,0 +1,46 @@
+<?xml version="1.0"?>
+<!--
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+<project default="antunit" xmlns:au="antlib:org.apache.ant.antunit">
+  <import file="../../antunit-base.xml" />
+
+  <target name="testBasedirOrFilesetRequired">
+    <au:expectfailure message="must specify basedir or fileset"
+                      expectedMessage="basedir attribute or one nested fileset is required!">
+      <cab/>
+    </au:expectfailure>
+  </target>
+
+  <target name="testOnlyOneFileset">
+    <au:expectfailure message="only one fileset is allowed"
+                      expectedMessage="Only one nested fileset allowed">
+      <cab>
+        <fileset dir="a"/>
+        <fileset dir="b"/>
+      </cab>
+    </au:expectfailure>
+  </target>
+
+  <target name="testCantHaveBasedirAndFileset">
+    <au:expectfailure message="can't have basedir and nested fileset"
+                      expectedMessage="Both basedir attribute and a nested fileset is not allowed">
+      <cab basedir=".">
+        <fileset dir="b"/>
+      </cab>
+    </au:expectfailure>
+  </target>
+</project>