Customize Maven command when deploying to Heroku

Question

We generate documentation from our tests with Spring REST Docs. When deploying the application to Heroku, by default tests are skipped, as I can see clearly in the logs:

-----> Java app detected
-----> Installing JDK 1.8... done
-----> Installing Maven 3.3.9... done
-----> Executing: mvn -DskipTests clean dependency:list install
[INFO] Scanning for projects...
[INFO]   

How can I customize the Maven command that is executed by Heroku?

Answer 1

After a day of searching, I found two possible ways to enable tests for the Heroku build:

1. Configure Maven Surefire Plugin in your pom.xml
2. Customize Heroku Java Buildpack

Maven Surefire Plugin

Configuration in your pom.xml overrides command-line arguments when your Maven process is started.

You can undo -DskipTests by disabling skipTests in the Maven Surefire Plugin configuration as follows:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>
        <skipTests>false</skipTests>
    </configuration>
</plugin>

Please note that Heroku adds environment variables when running Maven. Make sure you use an in-memory database when running in the Spring testprofile, otherwise the build will fail.

In my case, I use Flyway for database migrations. For some weird reason, regardless the spring.datasource.url in my application-test.yml, Flyway used the environment variable value. If you have the same issue, please note that you can override them too with the argLine configuration property of the Maven Surefire Plugin.

<argLine>-DDATABASE_URL=jdbc:h2:mem:questflair -DJDBC_DATABASE_URL=jdbc:h2:mem:questflair -DSPRING_DATASOURCE_URL=jdbc:h2:mem:questflair</argLine>

Heroku Java Buildpack

According to the Heroku Java Buildpack documentation, you can customize Maven options and goals.

I didn't try this solution, see Customize Maven for more information.