Junit 笔记
第一个单元测试
IDE基于Eclipse，基于Java8
测试类一般在类名上添加Test。
执行单元测试：Package Explorer▶right-click▶Run As ▶ JUnit Test
注意Fails和Errors的区别。
@FunctionalInterface
public interface Scoreable {
int getScore();
}
import java.util.*;
public class ScoreCollection {
private List<Scoreable> scores = new ArrayList<>();
public void add(Scoreable scoreable) {
scores.add(scoreable);
}
public int arithmeticMean() {
int total = scores.stream().mapToInt(Scoreable::getScore).sum();
return total / scores.size();
}
}
测试代码：
import static org.junit.Assert.*;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import static org.hamcrest.CoreMatchers.*;
public class ScoreCollectionTest {
@Before
public void setUp() throws Exception {
}
@After
public void tearDown() throws Exception {
}
@Test
public void answersArithmeticMeanOfTwoNumbers() {
// Arrange
ScoreCollection collection = new ScoreCollection();
collection.add(() -> 5);
collection.add(() -> 7);
// Act
int actualResult = collection.arithmeticMean();
// Assert
assertThat(actualResult, equalTo(6));
}
@Test
public void testArithmeticMean() {
fail("Not yet implemented");
}
}
真实案例
面试问卷调查系统
public class Answer {
private int i;
private Question question;
public Answer(Question question, int i) {
this.question = question;
this.i = i;
}
public Answer(Question characteristic, String matchingValue) {
this.question = characteristic;
this.i = characteristic.indexOf(matchingValue);
}
public String getQuestionText() {
return question.getText();
}
@Override
public String toString() {
return String.format("%s %s", question.getText(), question.getAnswerChoice(i));
}
public boolean match(int expected) {
return question.match(expected, i);
}
public boolean match(Answer otherAnswer) {
return question.match(i, otherAnswer.i);
}
public Question getCharacteristic() {
return question;
}
}
public enum Bool {
False(0),
True(1);
public static final int FALSE = 0;
public static final int TRUE = 1;
private int value;
private Bool(int value) { this.value = value; }
public int getValue() { return value; }
}
public class BooleanQuestion extends Question {
public BooleanQuestion(int id, String text) {
super(id, text, new String[] { "No", "Yes" });
}
@Override
public boolean match(int expected, int actual) {
return expected == actual;
}
}
import java.util.*;
public class Criteria implements Iterable<Criterion> {
private List<Criterion> criteria = new ArrayList<>();
public void add(Criterion criterion) {
criteria.add(criterion);
}
@Override
public Iterator<Criterion> iterator() {
return criteria.iterator();
}
public int arithmeticMean() {
return 0;
}
public double geometricMean(int[] numbers) {
int totalProduct = Arrays.stream(numbers).reduce(1, (product, number) -> product * number);
return Math.pow(totalProduct, 1.0 / numbers.length);
}
}
public class Criterion implements Scoreable {
private Weight weight;
private Answer answer;
private int score;
public Criterion(Answer answer, Weight weight) {
this.answer = answer;
this.weight = weight;
}
public Answer getAnswer() { return answer; }
public Weight getWeight() { return weight; }
public void setScore(int score) { this.score = score; }
public int getScore() { return score; }
}
public class PercentileQuestion extends Question {
public PercentileQuestion(int id, String text, String[] answerChoices) {
super(id, text, answerChoices);
}
@Override
public boolean match(int expected, int actual) {
return expected <= actual;
}
}
import java.util.*;
import java.util.stream.*;
public class Person {
private List<Question> characteristics = new ArrayList<>();
public void add(Question characteristic) {
characteristics.add(characteristic);
}
public List<Question> getCharacteristics() {
return characteristics;
}
public List<Question> withCharacteristic(String questionPattern) {
return characteristics.stream().filter(c -> c.getText().endsWith(questionPattern)).collect(Collectors.toList());
}
}
/*
// your answer
// their answer
// how important is it to you
me very organized
you very organized
very important
me no
you no
irrelevant 0
little 1
10
50
mandatory 250
how much did other person satisfy?
multiply scores
take nth root
.98 * .94 take sqrt (2 questions)
(geometric mean)
*/
import java.util.*;
public class Profile {
private Map<String,Answer> answers = new HashMap<>();
private int score;
private String name;
public Profile(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void add(Answer answer) {
answers.put(answer.getQuestionText(), answer);
}
public boolean matches(Criteria criteria) {
score = 0;
boolean kill = false;
boolean anyMatches = false;
for (Criterion criterion: criteria) {
Answer answer = answers.get(
criterion.getAnswer().getQuestionText());
boolean match =
criterion.getWeight() == Weight.DontCare ||
answer.match(criterion.getAnswer());
if (!match && criterion.getWeight() == Weight.MustMatch) {
kill = true;
}
if (match) {
score += criterion.getWeight().getValue();
}
anyMatches |= match;
}
if (kill)
return false;
return anyMatches;
}
public int score() {
return score;
}
}
public abstract class Question {
private String text;
private String[] answerChoices;
private int id;
public Question(int id, String text, String[] answerChoices) {
this.id = id;
this.text = text;
this.answerChoices = answerChoices;
}
public String getText() {
return text;
}
public String getAnswerChoice(int i) {
return answerChoices[i];
}
public boolean match(Answer answer) {
return false;
}
abstract public boolean match(int expected, int actual);
public int indexOf(String matchingAnswerChoice) {
for (int i = 0; i < answerChoices.length; i++)
if (answerChoices[i].equals(matchingAnswerChoice))
return i;
return -1;
}
}
public enum Weight {
MustMatch(Integer.MAX_VALUE),
VeryImportant(5000),
Important(1000),
WouldPrefer(100),
DontCare(0);
private int value;
Weight(int value) { this.value = value; }
public int getValue() { return value; }
}
其他文件和前面类似。
单元测试关注分支和潜在影响数据变化的代码。关注循环，if语句和复杂的条件句。如果值null或零？数据值如何影响的条件判断。
比如上面的Profile类需要关注：
for (Criterion criterion: criteria) 需要考虑Criteria无对象、很多对象的情况。
Answer answer = answers.get(criterion.getAnswer().getQuestionText()); 返回null的情况。 criterion.getAnswer()返回null或 criterion.getAnswer().getQuestionText()。
30行match返回true/false。类似的有34、37、42、44行。
两个分支的测试实例如下：
import org.junit.*;
import static org.junit.Assert.*;
public class ProfileTest {
private Profile profile;
private BooleanQuestion question;
private Criteria criteria;
@Before
public void create() {
profile = new Profile("Bull Hockey, Inc.");
question = new BooleanQuestion(1, "Got bonuses?");
criteria = new Criteria();
}
@Test
public void matchAnswersFalseWhenMustMatchCriteriaNotMet() {
profile.add(new Answer(question, Bool.FALSE));
criteria.add(
new Criterion(new Answer(question, Bool.TRUE), Weight.MustMatch));
boolean matches = profile.matches(criteria);
assertFalse(matches);
}
@Test
public void matchAnswersTrueForAnyDontCareCriteria() {
profile.add(new Answer(question, Bool.FALSE));
criteria.add(
new Criterion(new Answer(question, Bool.TRUE), Weight.DontCare));
boolean matches = profile.matches(criteria);
assertTrue(matches);
}
}
断言
断言有JUnit和Hamcrest, 前者的断言如下：
| 语句 | 描述 |
| assertTrue([message,] boolean condition) | 确认布尔条件为真。 |
| assertFalse([message,] boolean condition) | 确认布尔条件为假 |
| assertEquals([message,] expected, actual) | 确认返回等于期望，数组等比较的是地址而非内容。 |
| assertEquals([message,] expected, actual, tolerance) | 测试float或double相等。 tolerance为容许的误差。 |
| assertNull([message,] object) | 对象为null |
| assertNotNull([message,] object) | 对象非null |
| assertSame([message,] expected, actual) | 变量指向同一对象. |
| assertNotSame([message,] expected, actual) | 变量指向不同对象 |
Hamcrest的断言：assertThat。导入import static org.hamcrest.CoreMatchers.*;
组织测试
AAA(arrange, act, and assert) 可能还有After。
测试行为与方法：关注行为而不是方法，测试要尽量基于业务。
测试代码和产品代码分开。私有内容也尽量要测试。
单个测试方法的测试内容要尽量单一。
测试文档化；名字要能看出目的。比如doingSomeOperationGeneratesSomeResult、someResultOccursUnderSomeCondition、givenSomeContextWhenDoingSomeBehaviorThenSomeResultOccurs等
• Improve any local-variable names.
• Introduce meaningful constants.
• Prefer Hamcrest assertions.
• Split larger tests into smaller, more-focused tests.
• Move test clutter to helper methods and @Before methods.
另外有基于类的BeforeClass and AfterClass @Ignore可以忽略用例。