Build & Test Troubleshooting FAQ

Purpose: Reference guide for diagnosing and resolving build failures, test failures, and other development environment issues.

When to use: When encountering unexpected build or test failures, especially those that seem environment-related rather than code-related.

FAQ

Q1: NeoForge GameTest fails with "Illegal version number specified version (main)"

Symptoms:

File /path/to/neoforge-1.21.2/build/resources/main is not a valid mod file
Caused by: java.lang.IllegalArgumentException: Illegal version number specified version (main)

Cause: IDE (IntelliJ IDEA, Eclipse) generated bin/ directories containing unprocessed resource files. The neoforge.mods.toml in bin/main/META-INF/ has version="${version}" instead of the actual version number.