Split Tests Java

Divides a test suite into groups with equal execution time, based on prior test timings.

This ensures optimal parallel execution. Since test file runtimes can vary significantly, splitting them evenly without considering timing may result in inefficient grouping.

Compatibility

This tool was written for Java and released as JAR archive.

Usage

Download and extract the latest build from the releases page.

Using the command line

Execute the test split with the required arguments. The tool returns the set of test classes for the current split, joined by spaces.

java -jar split-tests-java.jar --split-index 0 --split-total 10 --glob '**/*Test.java'

Using a JUnit report

For example, check out the project into project and the JUnit reports into reports.

java -jar split-tests-java.jar --split-index 0 --split-total 10 --glob 'project/**/*Test.java' --junit 'reports/**/*.xml'

Arguments

Usage: <main class> [options]
  Options:
  * --split-index, -i
      This test split index.
      Default: 0
  * --split-total, -t
      Total number of test splits.
      Default: 0
  * --glob, -g
      Glob pattern to find test files. Make sure to single-quote the pattern 
      to avoid shell expansion.
    --calculate-optimal-total-split, -c
      Calculates the optimal test split (only on the first split index). Logs 
      a warning if --split-total does not match.
      Default: false
    --debug, -d
      Enables debug logging.
      Default: false
    --exclude-glob, -e
      Glob pattern to exclude test files. Make sure to single-quote the 
      pattern to avoid shell expansion.
    --format, -f
      The output format.
      Default: list
      Possible Values: [list, gradle]
    --help, -h
      Prints the usage.
    --junit-glob, -j
      Glob pattern to find JUnit reports. Make sure to single-quote the 
      pattern to avoid shell expansion.
    --max-optimal-total-split-calculations, -m
      The maximum number of --calculate-optimal-total-split calculations.
      Default: 50
    --new-test-time, -n
      Configures the calculation of the test time for tests without JUnit 
      reports. 
      Default: average
      Possible Values: [zero, average, min, max]
    --working-directory, -w
      The working directory. Defaults to the current directory.

Compilation

This tool is written in Java and uses Gradle as build tool.

• Install Java 21
• Checkout the repository
• ./gradlew shadowJar

Note

split-tests-java is inspired by split-test for Ruby.

In comparison to split-test, split-tests-java works with standard JUnit reports without a file or filepath attribute. The output are also fully qualified class names instead of file names. This makes it compatible with default Java tooling.