private ContentFileRetriever contentFileRetriever = new ContentFileRetrieverService();

    @Rule
    public TemporaryFolder tempFolder = new TemporaryFolder();

    @Before
    public void setup() {
        //here need to write content?
    }

    @Test
    public void getContentFile() throws IOException {
        File textFile = tempFolder.newFile("testText.txt");
        String pathFile = textFile.getPath();
        String[] testedContent = contentFileRetriever.getContentFile(pathFile);
        String[] expected = {"Line1 a", "Line2 b c", "Line 3"};
        assertArrayEquals(expected, testedContent);
    }