In-container unit tests (Docker TestNG integration)

With the advent of containerization of applications and the proliferation of micro-services, there arise a need to test containers similar to the way jar’s(java libraries) are tested using unit testing mechanisms. The example below demonstrates one such method that unitizes an environmental variable to trigger a TestNG test suite from outside a container. 

1.  Put in the test trigger code in your applications entry point as shown below,

	package org.testngrunner;
	import com.beust.jcommander.internal.Lists;
	import org.testng.TestNG;
	import java.util.List;
	public class App
	{
	public static void main( String[] args )
	{
	String trigger = System.getenv("EXEC_TYPE");
	if(trigger != null) {
	if(trigger.equals("TEST")) {
	TestNG testng = new TestNG();
	List<String> suites = Lists.newArrayList();
	suites.add("testng.xml");
	testng.setTestSuites(suites);
	testng.run();
	}
	}
	else {
	System.out.println("--- default execution flow of the component ---");
	}
	}
	}

view raw App.java hosted with ❤ by GitHub

2. Create a container consisting your application jar file(s), make sure all dependencies are available inside the container. In the example project the testng.xml file and a jar consisting of the application and its dependencies are copied into the container.

	FROM openjdk:8-jre-slim
	# Add the jar with all the dependencies
	ADD target/container-testngrunner.jar /usr/share/dumiduh/container-testngrunner.jar
	ADD testng.xml /usr/share/dumiduh/testng.xml
	WORKDIR /usr/share/dumiduh/
	ENTRYPOINT ["/usr/bin/java", "-cp", "container-testngrunner.jar","org.testngrunner.App"]

view raw testngcontainer hosted with ❤ by GitHub

3.  Run the container passing in the environmental variable as show below,

docker container run -e EXEC_TYPE=TEST containertestngsuite:1.0.0

view raw runcontainer.sh hosted with ❤ by GitHub

Find the example code base here[1]. Note that the container is made problematically using the docker main plugin.