Parallel execution of tests

Question

I've noticed that SBT is running my specs2 tests in parallel. This seems good, except one of my tests involves reading and writing from a file and hence fails unpredictably, e.g. see below.

Are there any better options than

1. setting all tests to run in serial,
2. using separate file names and tear-downs for each test?

class WriteAndReadSpec extends Specification{   val file = new File("testFiles/tmp.txt")    "WriteAndRead" should {     "work once" in {       new FileWriter(file, false).append("Foo").close       Source.fromFile(file).getLines().toList(0) must_== "Foo"     }     "work twice" in {       new FileWriter(file, false).append("Bar").close       Source.fromFile(file).getLines().toList(0) must_== "Bar"     }   }    trait TearDown extends After {     def after = if(file.exists) file.delete   } } 

Answer 1

In addition to that is written about sbt above, you must know that specs2 runs all the examples of your specifications concurrently by default.

You can still declare that, for a given specification, the examples must be executed sequentially. To do that, you simply add sequential to the beginning of your specification:

class WriteAndReadSpec extends Specification{   val file = new File("testFiles/tmp.txt")    sequential    "WriteAndRead" should {    ...   } } 

Answer 2

Fixed sequence of tests for suites can lead to interdependency of test cases and burden in maintenance.

I would prefer to test without touching the file system (no matter either it is business logic or serialization code), or if it is inevitable (as for testing integration with file feeds) then would use creating temporary files:

// Create temp file. File temp = File.createTempFile("pattern", ".suffix"); // Delete temp file when program exits. temp.deleteOnExit();