Question
What are the solutions for java.lang.OutOfMemoryError: Java heap space when running Maven tests?
Answer
The `java.lang.OutOfMemoryError: Java heap space` error occurs when the Java Virtual Machine (JVM) runs out of memory to allocate new objects. This is common during memory-intensive operations such as running tests using Maven, especially with larger projects or test suites.
// Set MAVEN_OPTS in a terminal or command line before running Maven commands.
export MAVEN_OPTS="-Xmx2048m" // For Unix-based systems
set MAVEN_OPTS=-Xmx2048m // For Windows systems
Causes
- Insufficient heap size allocation for the JVM.
- Memory leaks in the code or tests that fail to release allocated resources properly.
- Too many concurrent tests running at once, consuming excessive memory.
Solutions
- Increase the heap size for Maven by setting `MAVEN_OPTS` to a higher value, such as `-Xmx2048m` or even more depending on your system's resources.
- Review your test cases for potential memory leaks. Focus on ensuring objects get disposed of properly after tests are complete.
- Limit the number of concurrent threads used in tests to reduce peak memory consumption. This can be controlled in your project's Surefire plugin configuration.
Common Mistakes
Mistake: Not setting `MAVEN_OPTS` correctly before executing the Maven command.
Solution: Ensure `MAVEN_OPTS` is set in the same terminal session where Maven is executed.
Mistake: Over-relying on IDE settings that may not carry over to the command line.
Solution: Configure settings directly in your terminal or in a `settings.xml` file if using a CI/CD pipeline.
Mistake: Ignoring the results in `surefire-reports` for more insight into what tests are failing.
Solution: Check the reports for detailed error messages and stack traces related to the failing tests.
Helpers
- Maven OutOfMemoryError
- java.lang.OutOfMemoryError
- Maven tests
- increase Java heap size
- how to fix OutOfMemoryError