@Test @PrepareForTest(IOUtilities.class) public void testNativeCommandExecution() throws IOException { String[] directories = new String[] {"Directory 1", "Directory2", "Final Directory"}; StringBuilder builder = new StringBuilder(); for (String directory : directories) { builder.append(directory); builder.append("\n"); } mockRuntime(builder.toString()); String[] returnedDirectories = IOUtilities.executeNativeCommand(new String[] {"ls {0}"}, null, "stuff"); Assert.assertArrayEquals(directories, returnedDirectories); }