How can I make MSTest.exe return a 0 even if a test fails?

We have a build that runs on TeamCity and contains several different test projects. They each run one after the other, and we're using MSTest.exe from a Rakefile in order to orchestrate everything, thusly:

desc 'Run Unit Tests'
mstest :data_test => [:build_database_tests] do |mstest|
  puts build_header("Data Tests")
  mstest.command = msTestCommand
  mstest.parameters = [
            "/resultsfile:dTest.trx", 
            "/detail:errormessage", 
            "/detail:description",
            "/usestderr"

        ]
  mstest.assemblies  "../../../Database/DataTests/bin/Release/DataTests.dll"
end

This produces a nice TRX file that TeamCity can parse and everything, making for a nice clean report tab. However, the MSTest.exe returns a 1 if a test fails, which rake interprets as a failure, and causes the rest of the tests to not be run.

We would like to suppress this behavior; we want the build to continue to run when the test fails so that we can see what other tests may also fail. How can we get Rake to ignore the return code, and/or cause MSTest.exe to not emit a failing return code if a test fails?