java 如何在junit测试中测试比较器
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how to test Comparator at junit test
提问by nazar_art
I need to test this method - compare(). Can You get advice? How better I can do this(all part if, else-if, else).
我需要测试这个方法 - compare()。你能得到建议吗？我能做得多好（所有部分 if、else-if、else）。
public class AbsFigure {
class AreaCompare implements Comparator<FigureGeneral> {
@Override
public int compare(FigureGeneral oneFigure, FigureGeneral twoFigure) {
double firstValue = oneFigure.area();
double secondValue = twoFigure.area();
int result = 0;
if (firstValue > secondValue)
result = 1;
else if (firstValue < secondValue)
result = -1;
else
result = 0;
return result;
}
}
After this recomendations - we have next picture (Thank YOU guys a lot!):
在此推荐之后 - 我们有下一张照片（非常感谢你们！）：
public AreaCompare areaCompare = new AreaCompare();
@Test
public void testEqual() {
FigureGeneral oneFigure = new Rectangle(2.0, 2.0, "triangle");
FigureGeneral twoFigure = new Rectangle(2.0, 2.0, "rectangle");
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be equal", result == 0);
}
@Test
public void testGreaterThan() {
FigureGeneral oneFigure = new Triangle(2.0, 2.0, "triangle");
FigureGeneral twoFigure = new Rectangle(1.0, 1.0, "rectangle");
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be greater than", result >= 1);
}
@Test
public void testLessThan() {
FigureGeneral oneFigure = new Rectangle(1.0, 1.0, "rectangle");
FigureGeneral twoFigure = new Triangle(2.0, 2.0, "triangle");
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be less than", result <= -1);
All is normal testing now.
现在一切正常测试。
回答by munyengm
Just instantiate your comparator class and pass in objects:
只需实例化您的比较器类并传入对象：
public class Test extends TestCase {
class AreaCompare implements Comparator<FigureGeneral> {
@Override
public int compare(FigureGeneral oneFigure, FigureGeneral twoFigure) {
double firstValue = oneFigure.area();
double secondValue = twoFigure.area();
int result = 0;
if (firstValue > secondValue) {
result = 1;
} else if (firstValue < secondValue) {
result = -1;
} else {
result = 0;
}
return result;
}
}
private final AreaCompare areaCompare = new AreaCompare();
@Test
public void testEqual() {
FigureGeneral oneFigure = new FigureGeneral();
FigureGeneral twoFigure = new FigureGeneral();
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be equal", result == 0);
}
@Test
public void testGreaterThan() {
FigureGeneral oneFigure = new FigureGeneral();
FigureGeneral twoFigure = new FigureGeneral();
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be greater than", result >= 1);
}
@Test
public void testLessThan() {
FigureGeneral oneFigure = new FigureGeneral();
FigureGeneral twoFigure = new FigureGeneral();
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be less than", result <= -1);
}
}
回答by MrSmith42
Looks goof for me. Maybe get rid of result
对我来说看起来很傻。也许摆脱result
class AreaCompare implements Comparator<FigureGeneral> {
@Override
public int compare(FigureGeneral oneFigure, FigureGeneral twoFigure) {
double firstValue = oneFigure.area();
double secondValue = twoFigure.area();
if (firstValue > secondValue)
return 1;
else if (firstValue < secondValue)
return -1;
return 0;
}
}
Write at least test case. One for each return value.
至少编写测试用例。每个返回值一个。
compare(a, b)should have different sign than compare(b, a)or
compare(a, b)应该有不同于compare(b, a)或的符号
compare(a, b) == compare(b, a) == 0
compare(a, b) == compare(b, a) == 0
回答by Puce
I recently had a similar requirement and came up with some helper methods (not published as API yet, though). Here is the source code:
我最近有一个类似的需求，并提出了一些辅助方法（虽然尚未作为 API 发布）。这是源代码：
Here is a test, which uses these utility methods:
这是一个使用这些实用方法的测试：
回答by nazar_art
After a little bit advice, good test:
经过一点建议，良好的测试：
public AreaCompare areaCompare = new AreaCompare();
@Test
public void testEqual() {
FigureGeneral oneFigure = new Rectangle(2.0, 2.0, "triangle");
FigureGeneral twoFigure = new Rectangle(2.0, 2.0, "rectangle");
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be equal", result == 0);
}
@Test
public void testGreaterThan() {
FigureGeneral oneFigure = new Triangle(2.0, 2.0, "triangle");
FigureGeneral twoFigure = new Rectangle(1.0, 1.0, "rectangle");
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be greater than", result >= 1);
}
@Test
public void testLessThan() {
FigureGeneral oneFigure = new Rectangle(1.0, 1.0, "rectangle");
FigureGeneral twoFigure = new Triangle(2.0, 2.0, "triangle");
int result = areaCompare.compare(oneFigure, twoFigure);
assertTrue("expected to be less than", result <= -1);
}
回答by kap
It may be better to test for the contract and not for the -1/0/1 values (or more precisely, any positive/zero/negative value). This can be done using Hamcrest matchers in a very concise way. Consider the following example:
最好测试合约而不是 -1/0/1 值（或更准确地说，任何正/零/负值）。这可以以非常简洁的方式使用 Hamcrest 匹配器来完成。考虑以下示例：
import static org.hamcrest.Matchers.comparesEqualTo;
import static org.hamcrest.Matchers.greaterThan;
import static org.hamcrest.Matchers.lessThan;
public AreaCompare areaCompare = new AreaCompare();
@Test
public void testEqual() {
FigureGeneral oneFigure = new Rectangle(2.0, 2.0, "triangle");
FigureGeneral twoFigure = new Rectangle(2.0, 2.0, "rectangle");
assertThat(oneFigre comparesEqualTo(twoFigure));
assertThat(twoFigure, comparesEqualTo(oneFigure));
}
@Test
public void testGreaterThan() {
FigureGeneral oneFigure = new Triangle(2.0, 2.0, "triangle");
FigureGeneral twoFigure = new Rectangle(1.0, 1.0, "rectangle");
assertThat(oneFigure, greaterThan(twoFigure));
}
@Test
public void testLessThan() {
FigureGeneral oneFigure = new Rectangle(1.0, 1.0, "rectangle");
FigureGeneral twoFigure = new Triangle(2.0, 2.0, "triangle");
assertThat(oneFigure, lessThan(twoFigure));
}
Thus you do not have to remember which value stands for what and the tests make the intent clear.
因此，您不必记住哪个值代表什么，并且测试使意图清晰。
