### Question:
Calculator { public double multiply(double left, double right) { addToHistory(left, '*', right); return left * right; }  static Calculator getInstance(); double add(double left, double right); double subtract(double left, double right); double multiply(double left, double right); double divide(double left, double right); List<Operation> getOperations();  }### Answer:
@Test public void testMultiplication() throws Exception { assertEquals(5.0d, new Calculator().multiply(2.0d, 2.5d), 0.0000001d); }