Unit Test Framework


Available in v0.11.0 and later


You can write test cases for your tool by defining the tests() function in your Tool class. Test cases defined by this function will be picked up by janisdk run-test command.

This unit test framework provides several predefined preprocessors to transform Janis execution output data in the format that can be tested. For example, there is a preprocessor to read the md5 checksum of an output file. In addition to the predefined preprocessors, the frameworks also allows users to define and pass their own preprocessors.

Define test cases

You can define multiple test cases per tool. For each test case, you can declare multiple expected outputs. Mostly, you really only need to define more test cases if they require different input data.

The classes we use here janis_core.tool.test_classes.TTestCase, janis_core.tool.test_classes.TTestExpectedOutput and janis_core.tool.test_classes.TTestPreprocessor are declared at the bottom of this document.

class BwaAligner(BioinformaticsWorkflow):
    def id(self):
        return "BwaAligner"


    def tests(self):
        return [
                    "bam": "https://some-public-container/directory/small.bam"
                        expected_value="19384 + 0 in total (QC-passed reads + QC-failed reads)",

Run the tests

# Run a specific test case
janisdk run-test --test-case [TEST CASE NAME] [TOOL ID]

# Run ALL test cases of one tool
janisdk run-test [TOOL ID]

To run the example test case shown above:

# Run a specific test case
janisdk run-test --test-case=basic BwaAligner

# Run all test cases
janisdk run-test BwaAligner

Test Files

There are two different ways to store your test files (input and expected output files):

Remote HTTP files:

you can use a publicly accessible http link https://some-public-container/directory/small.bam.

  • Input files will be downloaded to a cache folder in ~/.janis/remote_file_cache folder. This is the same directory where files will be cached when you run janis run.
  • Expected output files however will be cached in the test directory [WORKING DIRECTORY WHERE janisdk run-test is run]/tests_output/cached_test_files/.

If the same url is found in the cache directory, we will not re-download the files unless the Last-Modified http header has changed. If you want to force the files to be re-downloaded, you will need to remove the files from the cache directories.

Local test files:

you can store your files in local directory named test_data. There are a few different examples of where you can place this directory. Example from janis-bioinformatics project:

  • A test_data folder that contain files to be shared by multiple tools can be located at janis_bioinformatics/tools/test_data. To access files in this directory, you can call os.path.join(BioinformaticsTool.test_data_path(), "small.bam").
  • A test_data folder that contain files to be used by flagstat can be located at janis_bioinformatics/tools/samtools/flagstat/test_data. To access files in this directory from within the SamToolsFlagstatBase class, you can call os.path.join(self.test_data_path(), "small.bam").

Preprocessors and Comparison Operators

TTestExpectedOutput.preprocessor is used to reformat the Tool output. TTestExpectedOutput.operator is used to compare output value with the expected output.

Predefined Preprocessors

  • Value: No preprocessing, value as output by Janis e.g. an integer, string, or a file path for a File type output.
  • FileDiff: The differences between two files as output by difflib.unified_diff. This can only be applied on File type output. If this preprocessor is used, TTestExpectedOutput.file_diff_source must be provided. file_diff_source must contain the file path to compare the output file with.
  • LinesDiff Number of different lines between two files as a tuple (additions, deletions), as diff’d by the FileDiff preprocessor. If this preprocessor is used, TTestExpectedOutput.file_diff_source must be provided. file_diff_source must contain the file path to compare the output file with.
  • FileContent: Extract the file content. This can only be applied to File type output.
  • FileExists: Check if a file exists. It returns a True/False value. This can only be applied to File type output.
  • FileSize: File size is bytes. This can only be applied on File type output.
  • FileMd5: Md5 checksum of a file. This can only be applied to File type output.
  • LineCount: Count the number of lines in a string or in a file.
  • ListSize: Count the number of items in a list. This can only be applied to Array type output.

Custom preprocessor example:

In this example below, we are testing a tool that has an output field named out. The output value of this field is a file path that points to the location of a BAM file. We want to test the flagstat value of this BAM file. Here, we define your custom preprocessor function that takes a file path as input and returns a string that contains the flagstat value of a BAM file.

TTestExpectedOutput.expected_file simply points to a file that contains the expected output value. You can also replace this with TTestExpectedOutput.expected_value="19384 + 0 in total (QC-passed reads + QC-failed reads)\n ..."

class Bam(File):

    def flagstat(cls, file_path: str):
        command = ["samtools", "flagstat", file_path]
        result = subprocess.run(

        if result.stderr:
            raise Exception(result.stderr)

        return result.stdout

Custom operator example:

In this example, we also want to test the flagstat value of BAM file returned by the out output field.

Here, instead of writing a custom preprocessors, we write a custom operator that takes two file path and compare the flagstat output of this two files.

class Bam(File):

    def equal(cls, file_path_1: str, file_path_2: str):
        flagstat1 = cls.flagstat(file_path_1)
        flagstat2 = cls.flagstat(file_path_2)

        return flagstat1 == flagstat2


class janis_core.tool.test_classes.TTestCase(name: str, input: Dict[str, Any], output: List[janis_core.tool.test_classes.TTestExpectedOutput])[source]

A test case requires a workflow or tool to be run once (per engine). But, we can have multiple output to apply different test logic.

class janis_core.tool.test_classes.TTestExpectedOutput(tag: str, preprocessor: Union[janis_core.tool.test_classes.TTestPreprocessor, Callable[[Any], Any]], operator: Callable[[Any, Any], bool], expected_value: Optional[Any] = None, expected_file: Optional[str] = None, file_diff_source: Optional[str] = None, array_index: Optional[int] = None, suffix_secondary_file: Optional[str] = None)[source]

Describe the logic on how to test the expected output of a test case. A test case can have multiple instances of this class to test different output or different logic of the same output

class janis_core.tool.test_classes.TTestPreprocessor[source]

An Enum class for a list of possible pre-processing we can do to output values