Comparing text files with Junit

java junit compare text-files
jon077 picture jon077 · Jan 21, 2009 · Viewed 55.3k times · Source

I am comparing text files in junit using:

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?

Answer

Jonik picture Jonik · Jan 21, 2009

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

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

Where file1 and file2 are File instances, and FileUtils is from 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.

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

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

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

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