groovier-junit

A Groovy Extension Module that makes JUnit 5 and 6 assertions more Groovy-friendly by adding improved BigDecimal comparison support.

Overview

This library extends JUnit's Assertions class with BigDecimal-aware assertion methods that use numerical comparison instead of strict equality. This solves the common problem where new BigDecimal("5.0") and new BigDecimal("5.00") are not considered equal by the standard assertEquals method, even though they represent the same numerical value.

Features

• Scale-insensitive BigDecimal comparison: Compares BigDecimals using compareTo() instead of equals()
• Seamless integration: Works automatically via Groovy's Extension Module mechanism
• Multiple overloads: Supports assertEquals(BigDecimal, BigDecimal) and assertEquals(Number, BigDecimal)
• JUnit 5 compatible: Extends the standard org.junit.jupiter.api.Assertions class

Installation

Gradle

Add the following dependency to your build.gradle:

dependencies {
    testImplementation 'se.alipsa.groovy:groovier-junit:0.2.0'
}

For Kotlin DSL (build.gradle.kts):

dependencies {
    testImplementation("se.alipsa.groovy:groovier-junit:0.2.0")
}

Maven

Add the following dependency to your pom.xml:

<dependency>
    <groupId>se.alipsa.groovy</groupId>
    <artifactId>groovier-junit</artifactId>
    <version>0.2.0</version>
    <scope>test</scope>
</dependency>

Usage

Once the library is on your classpath, the extension methods are automatically available. No additional configuration is needed.

Examples

import org.junit.jupiter.api.Assertions
import org.junit.jupiter.api.Test

class MyTest {

    @Test
    void testBigDecimalComparison() {
        // These assertions now pass, comparing numerical values instead of scale
        Assertions.assertEquals(5.0, 5.00G)
        Assertions.assertEquals(new BigDecimal("5.0"), new BigDecimal("5.00"))

        // Works with different Number types
        Assertions.assertEquals(5, 5.00G)
        Assertions.assertEquals(5.0d, 5.00G)
        Assertions.assertEquals(5L, 5.00G)
        Assertions.assertEquals(5G, 5.00G)
    }

    @Test
    void testWithCustomMessage() {
        // Custom failure messages are supported
        Assertions.assertEquals(100, 100.00G, "Account balance mismatch")
    }
}

Optional: Groovy-Friendly Test ClassLoader (Opt-In)

The assertion extensions work with zero extra setup.

If you also want Groovy-friendly classloader behavior for JUnit Platform launching (for example when using @Grab/Grape at runtime), enable the optional launcher interceptor.

System properties

• groovier.junit.classloader.enabled (default: false)
• groovier.junit.classloader.mode (optional: context or root, default: context)
• groovier.junit.classloader.debug (optional: true to print debug logs)

Gradle (JUnit Platform)

test {
  useJUnitPlatform()

  // Enable JUnit launcher interceptor auto-detection
  systemProperty 'junit.platform.launcher.interceptors.enabled', 'true'

  // Opt in to groovier-junit classloader support
  systemProperty 'groovier.junit.classloader.enabled', 'true'
  systemProperty 'groovier.junit.classloader.mode', 'context'
}

For @GrabConfig(systemClassLoader=true), the JVM must start with RootLoader as system classloader:

test {
  useJUnitPlatform()
  systemProperty 'junit.platform.launcher.interceptors.enabled', 'true'
  systemProperty 'groovier.junit.classloader.enabled', 'true'
  systemProperty 'groovier.junit.classloader.mode', 'root'
  jvmArgs '-Djava.system.class.loader=org.codehaus.groovy.tools.RootLoader'
}

Maven (Surefire/Failsafe)

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-surefire-plugin</artifactId>
  <version>3.5.4</version>
  <configuration>
    <systemPropertyVariables>
      <junit.platform.launcher.interceptors.enabled>true</junit.platform.launcher.interceptors.enabled>
      <groovier.junit.classloader.enabled>true</groovier.junit.classloader.enabled>
      <groovier.junit.classloader.mode>context</groovier.junit.classloader.mode>
    </systemPropertyVariables>
  </configuration>
</plugin>

For @GrabConfig(systemClassLoader=true), add:

<argLine>-Djava.system.class.loader=org.codehaus.groovy.tools.RootLoader</argLine>

Notes

• This feature is opt-in and does not affect users who only want assertion extensions.
• The interceptor can switch context classloader during launcher operations.
• It cannot retroactively replace the JVM system classloader after startup.

How It Works

The extension uses Groovy's Extension Module mechanism to add static methods to JUnit's Assertions class. When you call Assertions.assertEquals() with BigDecimal arguments, Groovy automatically dispatches to the enhanced version that uses compareTo() for comparison.

Standard JUnit behavior (without this extension):

assertEquals(new BigDecimal("5.0"), new BigDecimal("5.00"))  // FAILS - different scale

With groovier-junit:

assertEquals(new BigDecimal("5.0"), new BigDecimal("5.00"))  // PASSES - numerical equality

Requirements

• Java: 17 or higher
• Groovy: any 4.x or 5.x version should work
• JUnit: any 6.x version should work (probably earlier versions too)

Building from Source

git clone https://github.com/Alipsa/groovier-junit.git
cd groovier-junit
./gradlew build

Documentation

Generate GroovyDoc documentation:

./gradlew antGroovydoc

The documentation will be available in build/groovydocant/.

License

This project is licensed under the MIT License.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Author

Per Nyfelt

Links

• GitHub Repository
• Issue Tracker