使用 JUnit 进行单元测试

在这里,我们有一个类 Counter 与方法 countNumbers()hasNumbers()

public class Counter {

    /* To count the numbers in the input */
    public static int countNumbers(String input) {
        int count = 0;
        for (char letter : input.toCharArray()) {
            if (Character.isDigit(letter))
                count++;
        }
        return count;
    }

    /* To check whether the input has number*/
    public static boolean hasNumber(String input) {
        return input.matches(".*\\d.*");
    }
}

要对这个类进行单元测试,我们可以使用 Junit 框架。在项目类路径中添加 junit.jar。然后创建 Test case 类,如下所示:

import org.junit.Assert; // imports from the junit.jar
import org.junit.Test;

public class CounterTest {

    @Test // Test annotation makes this method as a test case
    public void countNumbersTest() {
        int expectedCount = 3;
        int actualCount = Counter.countNumbers("Hi 123");
        Assert.assertEquals(expectedCount, actualCount); //compares expected and actual value
    }

    @Test
    public void hasNumberTest() {
        boolean expectedValue = false;
        boolean actualValue = Counter.hasNumber("Hi there!");
        Assert.assertEquals(expectedValue, actualValue);
    }
}

在 IDE 中,你可以将此类作为 Junit testcase 运行,并在 GUI 中查看输出。在命令提示符下,你可以编译并运行测试用例,如下所示:

成功测试运行的输出应类似于:

JUnit version 4.9b2
..
Time: 0.019

OK (2 tests)

在测试失败的情况下,它看起来更像是:

Time: 0.024
There was 1 failure:
1) CountNumbersTest(CounterTest)
java.lang.AssertionError: expected:<30> but was:<3>
... // truncated output
FAILURES!!!
Tests run: 2,  Failures: 1