### Question:
DoubleArrayValueFormatter implements ValueFormatter<double[]> { @Override public String formatForCsv(double[] array) { return Arrays.stream(array).mapToObj(Double::toString).collect(joining(" ", "[", "]")); } private  DoubleArrayValueFormatter(); @Override String formatForCsv(double[] array); @Override String formatForDisplay(double[] array);  }### Answer:
@Test public void formatForCsv() { double[] array = {1, 2, 3}; assertThat(DoubleArrayValueFormatter.INSTANCE.formatForCsv(array)).isEqualTo("[1.0 2.0 3.0]"); }