Java 将文本文件与 Junit 进行比较

Comparing text files with Junit

提问by jon077

I am comparing text files in junit using:

我正在使用以下方法比较 junit 中的文本文件：

public static void assertReaders(BufferedReader expected,
          BufferedReader actual) throws IOException {
    String line;
    while ((line = expected.readLine()) != null) {
        assertEquals(line, actual.readLine());
    }

    assertNull("Actual had more lines then the expected.", actual.readLine());
    assertNull("Expected had more lines then the actual.", expected.readLine());
}

Is this a good way to compare text files? What is preferred?

这是比较文本文件的好方法吗？什么是首选？

采纳答案by IAdapter

junit-addonshas nice support for it: FileAssert

junit-addons对它有很好的支持：FileAssert

It gives you exceptions like:

它为您提供以下例外情况：

junitx.framework.ComparisonFailure: aa Line [3] expected: [b] but was:[a]

回答by Jon Skeet

If expected has more lines than actual, you'll fail an assertEquals before getting to the assertNull later.

如果预期的行数多于实际行数，则在稍后到达 assertNull 之前，您将失败 assertEquals。

It's fairly easy to fix though:

不过修复起来相当容易：

public static void assertReaders(BufferedReader expected,
    BufferedReader actual) throws IOException {
  String expectedLine;
  while ((expectedLine = expected.readLine()) != null) {
    String actualLine = actual.readLine();
    assertNotNull("Expected had more lines then the actual.", actualLine);
    assertEquals(expectedLine, actualLine);
  }
  assertNull("Actual had more lines then the expected.", actual.readLine());
}

回答by Stephen

I'd suggest using Assert.assertThat and a hamcrest matcher(junit 4.5 or later - perhaps even 4.4).

我建议使用 Assert.assertThat 和hamcrest 匹配器（junit 4.5 或更高版本 - 甚至可能是 4.4）。

I'd end up with something like:

我最终会得到类似的东西：

assertThat(fileUnderTest, containsExactText(expectedFile));

where my matcher is:

我的匹配器在哪里：

class FileMatcher {
   static Matcher<File> containsExactText(File expectedFile){
      return new TypeSafeMatcher<File>(){
         String failure;
         public boolean matchesSafely(File underTest){
            //create readers for each/convert to strings
            //Your implementation here, something like:
              String line;
              while ((line = expected.readLine()) != null) {
                 Matcher<?> equalsMatcher = CoreMatchers.equalTo(line);
                 String actualLine = actual.readLine();
                 if (!equalsMatcher.matches(actualLine){
                    failure = equalsMatcher.describeFailure(actualLine);
                    return false;
                 }
              }
              //record failures for uneven lines
         }

         public String describeFailure(File underTest);
             return failure;
         }
      }
   }
}

Matcher pros:

匹配器优点：

• Composition and reuse
• Use in normal code as well as test
  • Collections
  • Used in mock framework(s)
  • Can be used a general predicate function
• Really nice log-ability
• Can be combined with other matchers and descriptions and failure descriptions are accurate and precise

• 组合和重用
• 在普通代码和测试中使用
  • 收藏
  • 在模拟框架中使用
  • 可以使用一般谓词函数
• 非常好的日志能力
• 可与其他匹配器结合，描述和故障描述准确准确

Cons:

缺点：

• Well it's pretty obvious right? This is way more verbose than assert or junitx (for this particular case)
• You'll probably need to include the hamcrest libs to get the most benefit

• 嗯，这很明显吧？这比 assert 或 junitx 更冗长（对于这种特殊情况）
• 您可能需要包含 hamcrest 库才能获得最大收益

回答by Jonik

Here's one simple approach for checking if the files are exactlythe same:

这是检查文件是否完全相同的一种简单方法：

assertEquals("The files differ!", 
    FileUtils.readFileToString(file1, "utf-8"), 
    FileUtils.readFileToString(file2, "utf-8"));

Where file1and file2are Fileinstances, and FileUtilsis from Apache Commons IO.

Wherefile1和file2areFile实例，FileUtils来自Apache Commons IO。

Not much own code for you to maintain, which is always a plus. :) And very easy if you already happen to use Apache Commons in your project. But no nice, detailed error messages like in mark's solution.

没有多少自己的代码需要你维护，这总是一个加分项。:) 如果您已经在您的项目中使用了 Apache Commons，则非常容易。但是没有像mark 的解决方案那样好的、详细的错误消息。

Edit:
Heh, looking closer at the FileUtilsAPI, there's an even simpler way:

编辑：
嘿，仔细看看FileUtilsAPI，还有一种更简单的方法：

assertTrue("The files differ!", FileUtils.contentEquals(file1, file2));

As a bonus, this version works for all files, not just text.

作为奖励，此版本适用于所有文件，而不仅仅是文本。

回答by Scott Langley

Here is a more exhaustive list of File comparator's in various 3rd-party Java libraries:

以下是各种 3rd-party Java 库中文件比较器的更详尽列表：

• org.apache.commons.io.FileUtils
• org.dbunit.util.FileAsserts
• org.fest.assertions.FileAssert
• junitx.framework.FileAssert
• org.springframework.batch.test.AssertFile
• org.netbeans.junit.NbTestCase
• org.assertj.core.api.FileAssert

• org.apache.commons.io.FileUtils
• org.dbunit.util.FileAsserts
• org.fest.assertions.FileAssert
• junitx.framework.FileAssert
• org.springframework.batch.test.AssertFile
• org.netbeans.junit.NbTestCase
• org.assertj.core.api.FileAssert

回答by Mookie Wilson

FileUtilssure is a good one. Here's yet another simple approachfor checking if the files are exactly the same.

FileUtils肯定是个好的。这是检查文件是否完全相同的另一种简单方法。

assertEquals(FileUtils.checksumCRC32(file1), FileUtils.checksumCRC32(file2));

While the assertEquals() does provide a little more feedback than the assertTrue(), the result of checksumCRC32() is a long. So, that may not be intrisically helpful.

虽然 assertEquals() 确实比 assertTrue() 提供了更多的反馈，但 checksumCRC32() 的结果很长。所以，这可能没有内在的帮助。

回答by Bogdan Calmac

As of 2015, I would recomment AssertJ, an elegant and comprehensive assertion library. For files, you can assert against another file:

到 2015 年为止，我会推荐AssertJ，这是一个优雅而全面的断言库。对于文件，您可以针对另一个文件进行断言：

@Test
public void file() {
    File actualFile = new File("actual.txt");
    File expectedFile = new File("expected.txt");
    assertThat(actualFile).hasSameContentAs(expectedFile);
}

or against inline strings:

或针对内联字符串：

@Test
public void inline() {
    File actualFile = new File("actual.txt");
    assertThat(linesOf(actualFile)).containsExactly(
            "foo 1",
            "foo 2",
            "foo 3"
    );
}

The failure messages are very informative as well. If a line is different, you get:

失败消息也非常有用。如果一行不同，你会得到：

java.lang.AssertionError: 
File:
  <actual.txt>
and file:
  <expected.txt>
do not have equal content:
line:<2>, 
Expected :foo 2
Actual   :foo 20

and if one of the files has more lines you get:

如果其中一个文件有更多行，您会得到：

java.lang.AssertionError:
File:
  <actual.txt>
and file:
  <expected.txt>
do not have equal content:
line:<4>,
Expected :EOF
Actual   :foo 4

回答by Mauricio Gracia Gutierrez

This is my own implementation of equalFiles, no need to add any library to your project.

这是我自己的 实现equalFiles，无需在您的项目中添加任何库。

private static boolean equalFiles(String expectedFileName,
        String resultFileName) {
    boolean equal;
    BufferedReader bExp;
    BufferedReader bRes;
    String expLine ;
    String resLine ;

    equal = false;
    bExp = null ;
    bRes = null ;

    try {
        bExp = new BufferedReader(new FileReader(expectedFileName));
        bRes = new BufferedReader(new FileReader(resultFileName));

        if ((bExp != null) && (bRes != null)) {
            expLine = bExp.readLine() ;
            resLine = bRes.readLine() ;

            equal = ((expLine == null) && (resLine == null)) || ((expLine != null) && expLine.equals(resLine)) ;

            while(equal && expLine != null)
            {
                expLine = bExp.readLine() ;
                resLine = bRes.readLine() ; 
                equal = expLine.equals(resLine) ;
            }
        }
    } catch (Exception e) {

    } finally {
        try {
            if (bExp != null) {
                bExp.close();
            }
            if (bRes != null) {
                bRes.close();
            }
        } catch (Exception e) {
        }

    }

    return equal;

}

And to use it just use regular AssertTrueJUnit method

并使用它只需使用常规的AssertTrueJUnit 方法

assertTrue(equalFiles(expected, output)) ;

回答by Jonathan Andersson

Simple comparison of the content of two files with java.nio.fileAPI.

用java.nio.fileAPI简单比较两个文件的内容。

byte[] file1Bytes = Files.readAllBytes(Paths.get("Path to File 1"));
byte[] file2Bytes = Files.readAllBytes(Paths.get("Path to File 2"));

String file1 = new String(file1Bytes, StandardCharsets.UTF_8);
String file2 = new String(file2Bytes, StandardCharsets.UTF_8);

assertEquals("The content in the strings should match", file1, file2);

Or if you want to compare individual lines:

或者，如果您想比较各个行：

List<String> file1 = Files.readAllLines(Paths.get("Path to File 1"));
List<String> file2 = Files.readAllLines(Paths.get("Path to File 2"));

assertEquals(file1.size(), file2.size());

for(int i = 0; i < file1.size(); i++) {
   System.out.println("Comparing line: " + i)
   assertEquals(file1.get(i), file2.get(i));
}