Testing Java against Javascript implemenations

CompareRoundingImplementations.java

import static org.assertj.core.api.Assertions.assertThat;

import java.io.InputStreamReader;
import java.util.Random;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

import org.junit.Test;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class HoursRoundingTests {

	@Test
	public void test2DPRounding() throws ScriptException 
	{
		ScriptEngine engine = new ScriptEngineManager().getEngineByName("nashorn");
		engine.eval(new InputStreamReader(HoursRoundingTests.class.getResourceAsStream("/lodash.js")));
		
		Object object = engine.eval("_.VERSION");
		
		assertThat(object.getClass()).isEqualTo(String.class);
		assertThat(object.toString()).isEqualTo("4.17.11");
		
		log.warn("{} - {}", object.getClass(), object.toString());
		
		Random rand = new Random();
		for(int i=0;i<1000;i++){
			double nextDouble = rand.nextDouble();
			int nextInt = rand.nextInt(1000);
			double toTest = nextInt * nextDouble;
			
			double javaRounded = IncidentService.roundTo2dp(toTest);
			Double lodashRounded = (Double) engine.eval(String.format("_.round(%f, 2)", toTest));
			
			log.info("Round: {} - java:[{}] - lodash:[{}]", toTest, javaRounded, lodashRounded);
			
			assertThat(lodashRounded).isEqualTo(javaRounded).as("Round: %f - java:[%f] - lodash:[%f]", toTest, javaRounded, lodashRounded);
		}
	}

}