hibernate-demo/src/test/java/com/ankurm/hibernatedemo/testdb/StartupTimingTest.java

package com.ankurm.hibernatedemo.testdb;

import org.hibernate.SessionFactory;
import org.junit.jupiter.api.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Backs docs/09-testing-in-memory-databases.md, chapter "Startup time, with the caveat this is a shared
 * container". NOT a benchmark -- three runs per database, plain {@code System.nanoTime()},
 * one shared, likely-noisy sandbox container. The numbers are indicative of relative order of
 * magnitude only, and the docs/output file this writes says so explicitly.
 */
class StartupTimingTest {

    private static final Logger DEMO = LoggerFactory.getLogger("DEMO");

    private long timeOneBuild(TestDbSupport.Db db, String suffix) {
        long start = System.nanoTime();
        SessionFactory sf = TestDbSupport.buildSessionFactory(db, suffix, "create-drop", TestDbWidget.class);
        long elapsedMs = (System.nanoTime() - start) / 1_000_000;
        sf.close();
        return elapsedMs;
    }

    @Test
    void measureStartupAcrossThreeRunsPerDatabase() {
        TestDbSupport.Db[] dbs = {TestDbSupport.Db.H2, TestDbSupport.Db.HSQLDB, TestDbSupport.Db.DERBY};
        for (TestDbSupport.Db db : dbs) {
            long[] times = new long[3];
            for (int i = 0; i < 3; i++) {
                times[i] = timeOneBuild(db, "timing" + i);
            }
            DEMO.info("startup ms for {} over 3 runs: {}, {}, {} (sandbox container -- indicative only, not a benchmark)",
                    db, times[0], times[1], times[2]);
        }
    }
}