@Test
public void testTic() {

    // Create a GuitarString of frequency 11025, which
    // is an ArrayRingBuffer of length 4. 
    GuitarString s = new GuitarString(11025);
    s.pluck();
    // Record the front four values, ticcing as we go.
    double s1 = s.sample();
    s.tic();
    double s2 = s.sample();
    s.tic(); 
    double s3 = s.sample();
    s.tic();
    double s4 = s.sample();
    // If we tic once more, it should be equal to 0.996*0.5*(s1 + s2)
    s.tic();
    double s5 = s.sample();
    double expected = 0.996 * 0.5 * (s1 + s2);
    // Check that new sample is correct, using tolerance of 0.001.
    // See JUnit documentation for a description of how tolerances work
    // for assertEquals(double, double)
    assertEquals(expected, s5, 0.001);
}