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BastRTS is a tool to perform regression test selection.

Project description


Babel Regression Test Selection

A tool to perform regression test selection

BabelRTS saves time when testing code!

Given a codebase that has changed, this tool selects which tests are safe to execute. Only tests that involve changed code are selected. Tests that operate over untouched code shouldn't be run, so BabelRTS doesn't select them. Therefore it saves a lot of time when doing regression testing over large projects or with large test suites.

BabelRTS works well with many languages and it is based upon Dext, a tool that extracts file dependencies from code.

Run python -m babelrts -h for help.


Python >= 3.8 is required.

Note: this guide assumes that your python 3 installation is under the keyword python, however for most linux distribution it is under python3. If this is the case for you, just use python3instead of python.

The installation is done through python's package manager pip. Simply run:

python -m pip install babelrts


BabelRTS can be used as a stand alone module, or trough its API. The basic usage is:

python -m babelrts [-h] [-v] [-l <lang profile>] [-p <project folder>] [-t <test folder>] [-s <source folder>] [-o [<output>]]

Optional arguments:

  • -h,    --help                                        show help message and exit
  • -v,    --verbose                                   increase output verbosity
  • -l     <lang> [<lang> ...]                      set one or more languages (default all)
  • -p    <project folder>                         set project folder (default "current working directory")
  • -t     <test folder> [<test folder> ...]   set one or more test folders relative to <project folder> (default same as <project folder>)
  • -s    <source folders> [<source folder> ...]   set one or more source folders relative to <project folder> (default same as <project folder>)
  • -o     [<output>]                                 set output file (default "stdout")


The suggested workflow for using BabelRTS that will save time during testing

Write code

Run BabelRTS

Run tests



When run, this tool generates, inside the project folder, a new folder named .babelrts, which contains 4 files:

  • selected.json contains a json array with the paths to all the selected test files. This file should be used to instruct the testing utility on performing regression testing
  • hash.json contains a json object with all the sha1 of all the source files in the codebase
  • dependencies.json contains a json object with all the file dependencies in the codebase
  • changed.json contains a json array with all the changed classes since the previous BabelRTS run


BabelRTS API can be used by another script. Simply import babelrts to access its functions. Its main API is:

  • main(), to run the whole module as if it was called in the stand alone option.
  • run(langs, project_folder, test_folders, source_folders, verbose, output), to run BabelRTS passing your own arguments
  • rts(langs, project_folder, test_folders, source_folders), to run just the rts part

Example: runninf BabelRTS from another script.

#import BabelRTS module
>>> import babelrts

#run BabelRTS with language='java', project_folder='java-design-patterns/adapter/', test_folder='src/test', source_folder='src/main', verbose=False
>>> selected, dependencies, changed, new_hashes, test_files, source_files = babelrts.rts(['java'], 'java-design-patterns/adapter/', ['src/test'], ['src/main'])


BabelRTS supports many languages out of the box, including:

  • C
  • C++
  • C#
  • Erlang
  • Java
  • Javascript
  • Php
  • Python
  • Ruby
  • Rust
  • Scala

However many more languages are available. Read Dext Language Profiles for more info.

How it works

BabelRTS uses hashes to determine which files in a codebase have changed and then selects only tests that involve those files, thus saving a lot of time when running the test suite. The steps performed by BabelTS are:

  • hash all source files in a codebase
  • compare new hashes with the older ones
  • mark any file with different hash as "changed"
  • mark any new file as "changed"
  • compute graph of dependencies
  • select any test marked "changed"
  • select any test with at least one dependency marked "changed"
  • output selected tests
  • store hashes for next run


The advantages of using BabelRTS are:

  • it works with many languages
  • it's lightweight (just a few scripts)
  • it's lightning fast to run (faster than other RTS tools)
  • it saves a lot of time when used on large projects with large test suites
  • it doesn't require anything beside the code itself (other tools need things like the history of faults, class diagrams, integration with versioning tool...)
  • it's customizable

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