Java PathFinder (JPF) is a system to verify executable Java bytecode programs. In its basic form, it is a Java Virtual Machine (JVM) that is used as an explicit state software model checker, systematically exploring all potential execution paths of a program to find violations of properties like deadlocks or unhandled exceptions. Unlike traditional debuggers, JPF reports the entire execution path that leads to a defect. JPF is especially well-suited to finding hard-to-test concurrency defects in multithreaded programs.

websocketd is a small command-line tool that will wrap an existing command-line interface program, and allow it to be accessed via a WebSocket. WebSocket-capable applications can now be built very easily. As long as you can write an executable program that reads STDIN and writes to STDOUT, you can build a WebSocket server. Do it in Python, Ruby, Perl, Bash, .NET, C, Go, PHP, Java, Clojure, Scala, Groovy, Expect, Awk, VBScript, Haskell, Lua, R, whatever! No networking libraries necessary.

Clirr is a tool that checks Java libraries for binary and source compatibility with older releases. Basically you give it two sets of jar files and Clirr dumps out a list of changes in the public api. The Clirr Ant task can be configured to break the build if it detects incompatible api changes. In a continuous integration process Clirr can automatically prevent accidental introduction of binary or source compatibility problems.

Scala.js compiles Scala code to JavaScript, allowing you to write your web application entirely in Scala!

specs provides a BDD framework for the Scala language

IntelliJ IDEA is focused on raising your productivity by providing instant and clever code completion, on-the-fly code analysis, easy project navigation and reliable refactorings.

Rehersal is a testing framework for Scala, intended as an easier-to-use replacement for SUnit in the standard library.

Codacy is an automated code review platform for Python, Ruby, PHP, Java, JavaScript, Scala, C++, SWIFT and mode programming languages.

Users can check code for security and duplication issues, accuracy, complexity, coding style and other metrics. The platform also parses logs from code coverage tools and presents the evolution of code coverage side by side with the other software metrics. Codacy is configurable, allowing code patterns to be enabled or disabled. Codacy integrates with GitHub, Bitbucket, JIRA, YouTrack, Heroku, HipChat and Slack. It also offers an Enterprise version that runs in the clients' servers and integrates with Jenkins, GitHub Enterprise, Bitbucket Server and GitLab.

Lift is an expressive and elegant framework for writing web applications. Lift stresses the importance of security, maintainability, scalability and performance, while allowing for high levels of developer productivity.

ScalaCheck is a powerful tool for automatic unit testing of Scala and Java programs. It features automatic test case generation and minimization of failing test cases. ScalaCheck started out as a Scala port of the Haskell library QuickCheck, and has since evolved and been extended with features not found in Haskell QuickCheck.