Calculator.java

    1. package com.xzk;
    3. public class Calculator {
    4.     public int evaluate(String expression) {
    5.         int sum = 0;
    6.         for (String summand: expression.split("\\+")) {
    7.             sum += Integer.valueOf(summand);
    8.         }
    9.         return sum;
    10.     }
    11. }

    CalculatorTest.java

    1. package com.xzk;
    3. import static org.junit.Assert.assertEquals;
    4. import org.junit.Test;
    6. public class CalculatorTest {
    7.     @Test
    8.     public void evaluatesExpression() {
    9.         Calculator calculator = new Calculator();
    10.         int sum = calculator.evaluate("1+2+3");
    11.         assertEquals(6, sum);
    12.     }
    13. }