How to Solve java.lang.OutOfMemoryError: Java Heap Space During Maven Tests

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

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