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Usage of JUnit when it's private method.

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How to test the private method in junit.

Actually you can’t access the methods declared private thing. so You have to use the another way to test the below code.

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public class NaverConvertApi {

    /** It calculate the distances between two times taken from parameters */
    private String getTimeInterval(String dateTimeStr1, String dateTimeStr2) throws Exception {
        SimpleDateFormat dateFormat = new SimpleDateFormat("YYYYMMddHHmm");

        long dateTime1 = dateFormat.parse(dateTimeStr1).getTime();
        long dateTime2 = dateFormat.parse(dateTimeStr2).getTime();

        return Math.abs(dateTime1 - dateTime2) / 60000 + "";
    }         
}


Everythings are okay. but your code is declared as the private thing. I will use the reflection technique for solving it.

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public class NaverConvertApiTest {

    NaverConvertApi naverConvertApi = new NaverCovertApi();

    @Test
    public void GetTimeInterval_ShouldBe60() throws Exception {
        String dateTimeStr1 = "202007221635";
        String dateTimeStr2 = "202007221735";

        Method method = naverConvertApi.getClass().getDeclaredMethod("getTimeInterval", String.class, String.class);
        method.setAccessible(true);
   
        String result = (String) method.invoke(naverConvertApi, dateTimeStr1, dateTimeStr2);

        assertThat(result, is("60"));
    }
}

I think it is little complicated so someday i would like to introduce the easier technique for solving it using library named ‘PowerMock’

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