[SalesForce] Transfer managed package code to different SF org using Ant Migration Tool

Edit: Summer '15 made this "all better". If you upgrade your ant-salesforce.jar to one that supports API version 34, you can now pass a "testLevel=RunLocalTests" attribute to sf:deploy like so:

<sf:deploy
  testLevel="RunLocalTests" 
  username="${sf.username}" 
  password="${sf.password}" 
  serverUrl="${sf.server}" 
  deployRoot="src" 
  />

From the docs:

http://releasenotes.docs.salesforce.com/en-us/summer15/release-notes/rn_deployment_run_subset_of_tests.htm

As part of this change, the runAllTests deployment option is now replaced with testLevel. You can choose which tests to run in a deployment by setting the desired test level. For a description of all test levels, see test levels for the deploy() call. In particular, to run a subset of tests in a deployment, set testLevel to the RunSpecifiedTests value and specify the tests to run in the runTests option.

And

http://releasenotes.docs.salesforce.com/en-us/summer15/release-notes/rn_api_meta_new_calls.htm#testlevels

RunLocalTests—All tests in your organization are run, except the ones that originate from installed managed packages. This test level is the default for production deployments that include Apex classes or triggers.

This was the workaround for pre-Summer '15 for posterity:

Because I killed off the better part of a day hacking around in ant to accomplish the workaround @pepefloyd suggested, I wanted to publish a working example; In my case, the test classes are prefixed with "Test_" but you can fool around with the fileset as necessary

This is tested against v30 of the Force.com ant migration tool

<target name="test">
    <sfCompileAndTestUnmanaged checkOnly="true" username="${sf.username}" password="${sf.password}" server="${sf.server}">
        <fileset dir="src/classes">
            <include name="**/Test_*.cls"/>
        </fileset>
    </sfCompileAndTestUnmanaged>
</target>

<scriptdef name="sfCompileAndTestUnmanaged" language="javascript">
    <attribute name="checkonly"/>
    <attribute name="username"/>
    <attribute name="password"/>
    <attribute name="server"/>
    <attribute name="trace"/>
    <element name="fileset" type="fileset"/>

    <![CDATA[
        var filesets = elements.get("fileset");
        var filesetsIterator = filesets.iterator();
        var projectClasses = [];
        while(filesetsIterator.hasNext()){
            var fs = filesetsIterator.next();
            var iter = fs.iterator();
            while(iter.hasNext()){
                var resource = iter.next();
                var clazz = resource.getName().replace(".cls","");
                self.log("CLASS: " + clazz);
                projectClasses.push(clazz);
            }
        }

        var task = project.createTask("antlib:com.salesforce:compileAndTest");
        task.setCheckonly(attributes.get("checkonly") == 'true');
        task.setUsername(attributes.get("username"));
        task.setPassword(attributes.get("password"));
        task.setServer(attributes.get("server"));
        task.setTrace(attributes.get("trace") == 'true');

        //I tried 'importPackage' and conventional instantiation but couldn't get the inner class to instantiate; this works though
        var testsElement = task.getClass().getClassLoader().loadClass("com.salesforce.ant.CompileAndTest$RunTestsElement").newInstance();
        task.addRunTests(testsElement);

        var classClazz = task.getClass().getClassLoader().loadClass("com.salesforce.ant.CompileAndTest$CodeNameElement");
        for(i in projectClasses){
            var clazz = classClazz.newInstance();
            clazz.addText(projectClasses[i]);
            testsElement.addClass(clazz);
        }

        task.execute();
     ]]>
</scriptdef>

Alternatively, we've actually used a version of 'deploy' that does a no-op deploy (the package.xml in the 'ant' directory is empty except for the <version> element. This gives us incremental updates as the tests are running and allows the deployment of the source files to succeed in a separate ant target (not described below) while the tests may fail (insufficient code coverage, failing assertions, etc.)

<target name="test">
    <sfDeployUnmanaged purgeOnDelete="true" ignoreWarnings="true" username="${sf.username}" password="${sf.password}" serverUrl="${sf.server}" deployRoot="ant" maxPoll="75">
        <fileset dir="src/classes">
            <include name="**/*.cls"/>
        </fileset>
    </sfDeployUnmanaged>
</target>

<scriptdef name="sfDeployUnmanaged" language="javascript">
    <attribute name="purgeondelete"/>
    <attribute name="ignorewarnings"/>
    <attribute name="username"/>
    <attribute name="password"/>
    <attribute name="serverurl"/>
    <attribute name="deployroot"/>
    <attribute name="maxpoll"/>
    <attribute name="trace"/>
    <element name="fileset" type="fileset"/>

    <![CDATA[
        var filesets = elements.get("fileset");
        var filesetsIterator = filesets.iterator();
        var projectClasses = [];
        while(filesetsIterator.hasNext()){
            var fs = filesetsIterator.next();
            var iter = fs.iterator();
            while(iter.hasNext()){
                var resource = iter.next();
                var clazz = resource.getName().replace(".cls","");
                self.log("CLASS: " + clazz);
                projectClasses.push(clazz);
            }
        }

        var task = project.createTask("antlib:com.salesforce:deploy");
        task.setPurgeOnDelete(attributes.get("purgeondelete") == 'true');
        task.setIgnoreWarnings(attributes.get("ignorewarnings") == 'true');
        task.setUsername(attributes.get("username"));
        task.setPassword(attributes.get("password"));
        task.setServerURL(attributes.get("serverurl"));
        task.setDeployRoot(attributes.get("deployroot"));
        task.setMaxPoll(attributes.get("maxpoll"));
        task.setTrace(attributes.get("trace") == 'true');

        //Blows up when build timeout is reached if we don't set this (it uses this value when formatting the exception it throws)
        task.setOwningTarget(self.owningTarget);

        var classClazz = task.getClass().getClassLoader().loadClass("com.salesforce.ant.DeployTask$CodeNameElement");
        for(i in projectClasses){
            var clazz = classClazz.newInstance();
            clazz.addText(projectClasses[i]);
            task.addRunTest(clazz);
        }

        task.execute();
     ]]>
</scriptdef>

You need to configure Ant proxy settings. Standard way is to set the environment variable ANT_OPTS="-Dhttp.proxyHost=proxy -Dhttp.proxyPort=8080"