Package a TestJar for a Java Project

Most Spring Boot projects treat src/test/java as an internal implementation detail: it exists to make CI green and never leaves the build machine. But there’s a useful pattern that turns a subset of your tests into a portable, deployable artifact — one you can run after a deployment, against a real running environment, without needing a full dev toolchain, source checkout, or Maven installed on the target.

Once an application is deployed, you typically want a fast, focused check that the important paths actually work end-to-end: can it log in, can it reach the database, does the health endpoint respond, does a critical business flow complete. These are exactly the kind of tests you already write with JUnit — the only twist is where and when they run.

Step 1 — Tag the tests you want to select

Use JUnit 5’s @Tag to mark tests that should be treated as smoke/integration tests against a live system, as opposed to your regular unit tests that run on every build.

java

			
package com.example.app.smoke;
import io.restassured.RestAssured;
import org.junit.jupiter.api.Tag;
import org.junit.jupiter.api.Test;
import static io.restassured.RestAssured.given;
import static org.hamcrest.Matchers.equalTo;
@Tag("smoke")
class HealthEndpointSmokeTest {
    @Test
    void healthEndpointReportsUp() {
        RestAssured.baseURI = System.getenv().getOrDefault("BASE_URL", "http://localhost:8080");
        given()
            .when().get("/actuator/health")
            .then()
                .statusCode(200)
                .body("status", equalTo("UP"));
    }
}

		

java

			
@Tag("smoke")
class LoginFlowSmokeTest {
    @Test
    void userCanLogInAndFetchProfile() {
        // hits the real, deployed instance via BASE_URL
        // ...
    }
}

		

The key idea: these tests don’t use @SpringBootTest or an embedded context — they talk to a real, already-running instance over HTTP, addressed via an environment variable like BASE_URL.

Step 2 — Exclude the tag from the normal build, and build a separate artifact

Two things need to happen in pom.xml:

Your regular mvn test / mvn verify build should not run smoke tests (they need a live target and shouldn’t slow down or break the main build).
A separate, executable jar should be produced that contains only the compiled smoke test classes plus everything needed to run them standalone.

Excluding the tag from the default run

xml

			
<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>
        <excludedGroups>smoke</excludedGroups>
    </configuration>
</plugin>

		

Building a standalone, runnable test jar

The cleanest way to get a runnable jar for JUnit 5 tests is to bundle your compiled test classes together with the JUnit Platform Console Launcher, which can select and execute tests by tag from the command line. maven-shade-plugin builds the fat jar; maven-jar-plugin (via testJar goal) is not enough on its own since it won’t include dependencies.

xml

			
<build>
    <plugins>
        <!-- 1. Exclude smoke tests from the regular build -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <configuration>
                <excludedGroups>smoke</excludedGroups>
            </configuration>
        </plugin>
        <!-- 2. Build a fat jar containing test classes + console launcher -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-shade-plugin</artifactId>
            <executions>
                <execution>
                    <id>smoke-test-jar</id>
                    <phase>package</phase>
                    <goals>
                        <goal>shade</goal>
                    </goals>
                    <configuration>
                        <shadedArtifactAttached>true</shadedArtifactAttached>
                        <shadedClassifierName>smoke-tests</shadedClassifierName>
                        <transformers>
                            <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                <mainClass>org.junit.platform.console.ConsoleLauncher</mainClass>
                            </transformer>
                        </transformers>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>
<dependencies>
    <dependency>
        <groupId>org.junit.jupiter</groupId>
        <artifactId>junit-jupiter</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.junit.platform</groupId>
        <artifactId>junit-platform-console-standalone</artifactId>
        <version>1.10.2</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>io.rest-assured</groupId>
        <artifactId>rest-assured</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

		

This produces myapp-1.4.2-smoke-tests.jar, runnable directly:

bash

			
java -jar myapp-1.4.2-smoke-tests.jar --select-package com.example.app.smoke --include-tag smoke

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