public Set<String> getApplicationNames() {
        ImmutableSet.Builder<String> names = ImmutableSet.builder();
        File[] files = appsDir.listFiles(File::isDirectory);
        if (files != null) {
            for (File file : files) {
                names.add(file.getName());
            }
        }
        return names.build();
    }
@Test
    public void getAppNames() throws IOException {
        saveZippedApp();
        Set<String> names = aar.getApplicationNames();
        assertEquals("incorrect names", ImmutableSet.of(APP_NAME), names);
    }