"application/vnd.oma.group-usage-list+xml",
				"application/vnd.oma.poc.detailed-progress-report+xml",
				"application/vnd.oma.poc.final-report+xml",
				"application/vnd.oma.poc.groups+xml",
				"application/vnd.oma.poc.invocation-descriptor+xml",
				"application/vnd.oma.poc.optimized-progress-report+xml",
				"application/vnd.oma.xcap-directory+xml",
				"application/vnd.omads-email+xml",

			actual = f(tc.in, tc.arg)
		} else {
			actual = fb(tc.in, []byte(tc.arg))
		}
		report := func(s []byte) string {
			if s == nil {
				return "nil"
			} else {
				return fmt.Sprintf("%q", s)
			}
		}
		if len(actual) != 0 {
			t.Errorf("%s(%s, %q) returned non-empty value", name, report(tc.in), tc.arg)
		} else {
			actualNil := actual == nil
			outNil := tc.out == nil