return new CharSource() {
      @Override
      public Reader openStream() {
        return new StringReader(text);
      }
    };
  }

  public void testSkip() throws Exception {
    String begin = "abcde";
    String end = "fghij";
    Reader joinedReader = CharSource.concat(newCharSource(begin), newCharSource(end)).openStream();

    String expected = begin + end;
    assertEquals(expected.charAt(0), joinedReader.read());

  public void testReadEmptyString() throws IOException {
    assertReadsCorrectly("");
  }

  public void testReadsStringsCorrectly() throws IOException {
    assertReadsCorrectly("abc");
    assertReadsCorrectly("abcde");
    assertReadsCorrectly("abcdefghijkl");
    assertReadsCorrectly(
        ""
            + "abcdefghijklmnopqrstuvwxyz\n"
            + "ABCDEFGHIJKLMNOPQRSTUVWXYZ\r"
            + "0123456789\r\n"

        Graph graph2 = new Graph();
        addEdge(graph2, "a", "b");
        addEdge(graph2, "b", "c");
        CycleDetectedException cde = assertThrows(CycleDetectedException.class, () -> addEdge(graph2, "c", "a"));
        List<String> cycle = cde.getCycle();
        assertNotNull(cycle, "Cycle should be not null");
        assertTrue(cycle.contains("a"), "Cycle contains 'a'");

    return new CharSource() {
      @Override
      public Reader openStream() {
        return new StringReader(text);
      }
    };
  }

  public void testSkip() throws Exception {
    String begin = "abcde";
    String end = "fghij";
    Reader joinedReader = CharSource.concat(newCharSource(begin), newCharSource(end)).openStream();

    String expected = begin + end;
    assertEquals(expected.charAt(0), joinedReader.read());

  public void testReadEmptyString() throws IOException {
    assertReadsCorrectly("");
  }

  public void testReadsStringsCorrectly() throws IOException {
    assertReadsCorrectly("abc");
    assertReadsCorrectly("abcde");
    assertReadsCorrectly("abcdefghijkl");
    assertReadsCorrectly(
        ""
            + "abcdefghijklmnopqrstuvwxyz\n"
            + "ABCDEFGHIJKLMNOPQRSTUVWXYZ\r"
            + "0123456789\r\n"