How to unit test a method that reads a given file

Question

I know this is a bit naive. How to unit test this piece of code without giving physical file as input. I am new to mockito and unit testing. So I am not sure. Please help.

Answer 1

You can create a file as part of the test, no need to mock it out.

JUnit does have a nice functionality for creating files used for testing and automatically cleaning them up using the TemporaryFolder rule.

public class MyTestClass {

    @Rule
    public TemporaryFolder folder = new TemporaryFolder();

    @Test
    public void myTest() {
        // this folder gets cleaned up automatically by JUnit
        File file = folder.newFile("someTestFile.txt");

        // populate the file
        // run your test
    }
}