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INET contains a comprehensive test suite. The test suite can be found under the tests folder. Testing is usually done from the command line after setting up the environment with:

$ cd ~/workspace/omnetpp
$ . setenv
$ cd ~/workspace/inet
$ . setenv

Regression Testing

The most often used tests are the so called fingerprint tests, which are generally useful for regression testing. Fingerprint tests are a low-cost but effective tool for regression testing of simulation models during development. For more details on fingerprint testing, please refer to the OMNeT++ manual.

The INET fingerprint tests can be found under the tests/fingerprint folder. Each test is basically a simulation scenario described by one line in a CSV file. INET contains several such CSV files for different groups of tests. One CSV line describes a simulation by specifying the working directory, command line arguments, simulation time limit, expected fingerprint and test result (e.g. pass or fail), and several user defined tags to help filtering.

Fingerprint tests can be run using the fingerprinttest script found in the above folder. To run all fingerprint tests, simply run the script without any arguments:

$ ./fingerprinttest

The script also has various command line arguments, which can be understood by asking for help with:

$ ./fingerprinttest -h

Running all INET fingerprint tests takes several minutes even on a modern computer. By default, the script utilizes all available CPUs, the tests are run in parallel (non-deterministic order).

The simplest way to make the tests run faster, is to run only a subset of all fingerprint tests. The script provides a filter parameter (-m) which takes a regular expression that is matched against all information of the test.

Another less commonly used technique is running the fingerprint tests in release mode. One disadvantage of release mode is that certain assertions, which are conditionally compiled, are not checked.

For example, the following command runs all wireless tests in release mode:

$ ./fingerprinttest --release -m wireless

While the tests are running, the script prints some information about each test followed by the test result. The test result is either PASS, FAIL or ERROR (plus some optional details):

/examples/bgpv4/BgpAndOspfSimple/ -f omnetpp.ini -c config1 -r 0 ... : PASS
/examples/bgpv4/BgpCompleteTest/ -f omnetpp.ini -c config1 -r 0 ... : FAIL

When testing is finished, the script also prints a short summary of the results with the total number of tests, failures and errors:

  /examples/bgpv4/BgpCompleteTest/ -f omnetpp.ini -c config1 -r 0
Ran 2 tests in 3.615s

FAILED (failures=1)

Apart from the information printed on the console, fingerprint testing also produces three CSV files. One for the updated fingerprints, one for the failed tests, and one for the test which couldn’t finish without an error. The updated file can be used to overwrite the original CSV file to accept the new fingerprints.

Usually, when a simulation model is being developed, the fingerprint tests should be run every now and then, to make sure there are no regressions (i.e. all tests run with the expected result). How often tests should be run depends on the kind of development, tests may be run from several times a day to a few times a week.

For example, if a completely new simulation model is developed with new examples, then the new fingerprint tests can be run as late as when the first version is pushed into the repository. In contrast, during an extensive model refactoring, it’s adivsable to run the affected tests more often (e.g. after each small step). Running the tests more often helps avoiding getting into a situation where it’s difficult to tell if the new fingerprints is acceptable or not.

In any case, certain correct changes in the simulation model break fingerprint tests. When this happens, there are two ways to validate the changes:

  • One is when the changes are further divided until the smallest set of changes are found, which still break fingerprints. In this case, this set is carefully reviewed (potentially by multiple people), and if it is found to be correct, then the fingerprint changes are simply accepted.

  • The other is to actually change the fingerprint calculation in a way that ignores the effects of the set of changes. To this end, you can change the fingerprint ingredients, use filtering, or change the fingerprint calculation algorithm in C++. These options are covered in the OMNeT++ manual.

    With this method, the fingerprint tests must be re-run before the changes are applied using the modified fingerprint calculation. The updated fingerprint CSV files must be used to run the fingerprint tests after applying the changes. This method is often time consuming, but may be worth the efforts for complex changes, because it allows having a far greater confidence in correctness.

For a simple example, a timing change which neither changes the order of events nor where the events happen, can be easily validated by changing the fingerprint and removing time from the ingredients (default is tplx) as follows:

./fingerprinttest -a --fingerprint=0 --fingerprint-ingredients=plx

Another common example is when a submodule is renamed. Since the default fingerprint ingredients contain the full module path of all events, this change will break fingerprint tests. If the module is not optional or not accessed by other modules using its name, then removing the module path from the fingerprint ingredients (i.e. using tlx) can be used to validate this change.

For a more complicated example, when the IEEE 802.11 MAC (very complex) model is refactored to a large extent, then it’s really difficult to validate the changes. If despite the changes, the model is expected to keep its external behavior, then running the fingerprint tests can be used to prove this to some extent. The easy way to do this is to actually ignore all events executed by the old and the new IEEE 802.11 MAC models:

# please note the quoting uses both ' and " in the right order
./fingerprinttest -a --fingerprint-modules='"not(fullPath(**.wlan[*].mac.**))"'

INET uses continuous integration on Github. Fingerprint and other tests are run automatically for changes on the master and integration branches. Moreover, all submitted pull requests are automatically tested the same way. The result of the test suite is clearly marked on the pull request with check mark or a red cross.

In general, contributors are expected to take care of not breaking the fingerprint tests. In case of a necessary fingerprint change, the CSV files should be updated in separate patches.

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