Gradle Test Synchronization Plugin

A gradle plugin that provides a way to synchronize tests between different gradle modules.

Motivation

Consider following project structure:

root
  build.gradle
  settings.gradle
  +-- module1
    build.gradle
  +-- module2
    build.gradle

Both modules have API tests that call some external service. You want to build / tests these modules in parallel (with gradle property org.gradle.parallel=true), but external API has a rate limit that causes tests to fail when run in parallel. You can't simply synchronize tests by using some static state or JUnit built-in synchronization tools (@ResourceLock, @Isolated, etc), because tests are run in different JVMs. One possible solution is to move all tests to new single module, but this is not always desirable or possible.

This plugin aims to solve exactly this problem.

Usage

Synchronizing based on single tag

In build.gradle(.kts):

plugins {
    id("com.varlanv.testsync").version("0.0.1")
}

testSync {
    tag("postgres")
}

In junit test in gradle submodule "A":

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Tag;

class SubmoduleAPostgresTest {

    @Test
    @Tag("postgres")
    void test() {
        // ...
    }
}

In junit test in gradle submodule "B":

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Tag;

class SubmoduleBPostgresTest {

    @Test
    @Tag("postgres")
    void test() {
        // ...
    }
}

In this example, tests SubmoduleAPostgresTest and SubmoduleBPostgresTest will be synchronized and run one after another.

Synchronizing based on multiple tags

In build.gradle(.kts):

plugins {
    id("com.varlanv.testsync").version("0.0.1")
}

testSync {
    tags("postgres", "mongo")
}

In junit tests:

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Tags;

class PostgresTest {

    @Test
    @Tag("postgres")
    void test() {
        // ...
    }
}

class MongoTest {

    @Test
    @Tag("mongo")
    void test() {
        // ...
    }
}

class MongoWithPostgresTest {

    @Test
    @Tags({@Tag("postgres"), @Tag("mongo")})
    void test() {
        // ...
    }
}

In this example:

• All tests tagged "postgres" or "mongo" will have independent locks, allowing them to run independently and in parallel.
• Tests that are tagged with both "postgres" AND "mongo" will (wait and) acquire both locks. When the locks are acquired, no other "postgres" or "mongo" will be allowed to start until locks are released.

Optimization

The plugin is built to support all of the major Gradle optimization features, such as:

• Parallel builds (as this is whole point of plugin)
• Build cache
• Configuration cache
• Isolated projects

Known limitations

• Currently, only JUnit 5 is supported
• Synchronization is possible only by using Junit tags (org.junit.jupiter.api.Tag).
• The plugin was tested with latest Gradle 8x, 7x, 6x versions (8.14, 7.6.1, 6.9.4). Any other version is not guaranteed to work. But most likely any version in range 7.x.x - 8.x.x will work, since plugin does not rely on any unstable internal Gradle API.

If you have any issues or feature requests, please don't hesitate to create an issue.

License

This project is distributed under the MIT License.