【Code】《代码整洁之道》笔记-Chapter15-JUnit内幕

第15章　JUnit内幕

JUnit是最有名的Java框架之一。就像别的框架一样，它概念简单，定义精确，实现优雅。但它的代码是怎样的呢？本章将研判来自JUnit框架的一个代码例子。

15.1　JUnit框架

JUnit有很多位作者，但它始于Kent Beck和Eric Gamma一次去亚特兰大的飞行旅程。Kent想学Java，而Eric则打算学习Kent的Smalltalk测试框架。“对于两个身处狭窄空间的极客，还有什么会比拿出笔记本电脑开始编码来得更自然呢？”经过3小时高海拔工作，他们写出了JUnit的基础代码。

我们要查看的模块，是用来帮忙鉴别字符串比较错误的一段聪明代码，该模块被命名为ComparisonCompactor。对于两个不同的字符串，如ABCDE和ABXDE，该模块将用形如<...B[X]D...>的字符串来曝露两者的不同之处。

我们可以做进一步解释，但测试用例会更有说服力。看看代码清单15-1，我们将深入了解到该模块满足的需求，边看代码，边研究该测试的结构，它们能变得更简洁或更明确吗？

代码清单15-1　ComparisonCompactorTest.java

package junit.tests.framework;

import junit.framework.ComparisonCompactor;
import junit.framework.TestCase;

public class ComparisonCompactorTest extends TestCase {

  public void testMessage() {
    String failure= new ComparisonCompactor(0, "b", "c").compact("a");
    assertTrue("a expected:<[b]> but was:<[c]>".equals(failure));
  }

  public void testStartSame() {
    String failure= new ComparisonCompactor(1, "ba", "bc").compact(null);
    assertEquals("expected:<b[a]> but was:<b[c]>", failure);
  }

  public void testEndSame() {
    String  failure= new ComparisonCompactor(1, "ab", "cb").compact(null);
    assertEquals("expected:<[a]b> but was:<[c]b>", failure);
  }

  public void testSame() {
    String failure= new ComparisonCompactor(1, "ab", "ab").compact(null);
    assertEquals("expected:<ab> but was:<ab>", failure);
  }

  public void testNoContextStartAndEndSame() {
    String failure= new ComparisonCompactor(0, "abc", "adc").compact(null);
    assertEquals("expected:<...[b]...> but was:<...[d]...>", failure);
  }

  public void testStartAndEndContext() {
    String failure= new ComparisonCompactor(1, "abc", "adc").compact(null);
    assertEquals("expected:<a[b]c> but was:<a[d]c>", failure);
  }

  public void testStartAndEndContextWithEllipses() {
    String failure= 
      new ComparisonCompactor(1, "abcde", "abfde").compact(null);
    assertEquals("expected:<...b[c]d...> but was:<...b[f]d...>", failure);
  }

  public void testComparisonErrorStartSameComplete() {
    String failure= new ComparisonCompactor(2, "ab", "abc").compact(null);
    assertEquals("expected:<ab[]> but was:<ab[c]>", failure);
  }

  public void testComparisonErrorEndSameComplete() {
    String failure= new ComparisonCompactor(0, "bc", "abc").compact(null);
    assertEquals("expected:<[]...> but was:<[a]...>", failure);
  }

  public void testComparisonErrorEndSameCompleteContext() {
    String failure= new ComparisonCompactor(2, "bc", "abc").compact(null);
    assertEquals("expected:<[]bc> but was:<[a]bc>", failure);
  }

  public void testComparisonErrorOverlapingMatches() {
    String failure= new ComparisonCompactor(0, "abc", "abbc").compact(null);
    assertEquals("expected:<...[]...> but was:<...[b]...>", failure);
  }

  public void testComparisonErrorOverlapingMatchesContext() {
    String failure= new ComparisonCompactor(2, "abc", "abbc").compact(null);
    assertEquals("expected:<ab[]c> but was:<ab[b]c>", failure);
  }

  public void testComparisonErrorOverlapingMatches2() {
    String failure= new ComparisonCompactor(0, "abcdde", "abcde").compact(null);
    assertEquals("expected:<...[d]...> but was:<...[]...>", failure);
  }

  public void testComparisonErrorOverlapingMatches2Context() {
    String failure= 
      new ComparisonCompactor(2, "abcdde", "abcde").compact(null);
    assertEquals("expected:<...cd[d]e> but was:<...cd[]e>", failure);
  }

  public void testComparisonErrorWithActualNull() {
    String failure= new ComparisonCompactor(0, "a", null).compact(null);
    assertEquals("expected:<a> but was:<null>", failure);
  }

  public void testComparisonErrorWithActualNullContext() {
    String failure= new ComparisonCompactor(2, "a", null).compact(null);
    assertEquals("expected:<a> but was:<null>", failure);
  }

  public void testComparisonErrorWithExpectedNull() {
    String failure= new ComparisonCompactor(0, null, "a").compact(null);
    assertEquals("expected:<null> but was:<a>", failure);
  }

  public void testComparisonErrorWithExpectedNullContext() {
    String failure= new ComparisonCompactor(2, null, "a").compact(null);
    assertEquals("expected:<null> but was: