### Question:
SubtractionOperation implements Operation { @Override public int calculate(int a, int b) { return a - b; }  @Override int calculate(int a, int b); @Override String name();  }### Answer:
@Test public void testSubtraction() { Operation op = new SubtractionOperation(); assertThat(op.calculate(5, 2)).isEqualTo(3); assertThat(op.calculate(10, 5)).isEqualTo(5); assertThat(op.calculate(4, 2)).isEqualTo(2); }