Quilt
Quilt is a Java software development tool that measures coverage , the extent to which unit testing exercises the software under test. It is optimized for use with the JUnit unit test package, the Ant Java build facility, and the Maven project management toolkit.

Quilt is currently undergoing a major transformation. The first release of the new version, 0.6a, became available on 31 August 2003. This is now forking off as a separate project while development of the 0.4/0.5 branch will continue at Codehaus.

EMMA
EMMA is an open-source toolkit for measuring and reporting Java code coverage. Until recently, the world of Java development had been plagued by an absurd discrepancy: Java developers had excellent free IDEs, free compilers, free test frameworks but had to rely on code coverage tools that charged an arm and a leg in license fees. As a Java pro, I would like to use the same free coverage tool regardless of whether it is a massive commercial project at work or a small fun project at home. I've created EMMA to be that tool.

EMMA is an open-source toolkit for measuring and reporting Java code coverage. It distinguishes itself from other tools by going after a unique feature combination: support for large-scale enterprise software development while keeping individual developer's work fast and iterative. Every developer on your team can now get code coverage for free and they can get it fast!

NoUnit - 

Great ! - You're into Extreme Programming. You've written the tests ( JUnit of course). You've done the most simple thing that could possibly work. You've even shared your keyboard with a colleague. But have you done enough?

NoUnit allows you to see how good your JUnit tests are

'Test everything that could possibly break' is the motto. But how good are the tests you've written? Are they missing any part of your code? Are you testing too much? Is something being tested only via 5 or 6 nested calls?

NoUnit answers these questions by giving you a simple picture of your code. Like a Graph , NoUnit shows you a picture of your code , and reveals how good your JUnit tests are.

• Gives you clear pictures of your code and tests (Green is good , Red is bad!).
• Is a 100% Java and XML solution , freely available under the GNU License.
• Can be extended to show any code pictures you want (Any view of your code , not just JUnit tests!)

Reports can be understood by anybody , including non-techies :-)

. It generates a report from your code to graphically show you how many of your project's methods are being tested , and how well.

InsECT
InsECT which stands for Instrumentation Execution Coverage Tool, is a system developed in Java to obtain coverage information for Java programs. InsECT instruments (inserts instructions into) Java class files at the bytecode level with probes to report information about a system at runtime. The goal of InsECT is to provide detailed coverage information about Java programs by taking into full account the object-oriented behavior and language features of Java. Furthermore, as an open-source project, InsECT is designed to be extensible for use in a wide variety of dynamic analyses. InsECT utilizes the Byte Code Engineering Library.

Hansel
Hansel is an extension to JUnit that adds code coverage testing to the testing framework. Most tools try to generate code coverage reports from a test-run of all available tests.
But a much more useful information is how much of the code which a test is supposed to test is covered. Hansel gives you this information.

Jester
Jester finds code that is not covered by tests. Jester makes some change to your code, runs your tests, and if the tests pass Jester displays a message saying what it changed. Jester includes a script for generating web pages that show the changes made that did not cause the tests to fail.

Jester is different than code coverage tools, because it can find code that is executed by the running of tests but not actually tested. Jester's approach is called mutation testing or automated error seeding. However, Jester is not meant as a replacement for code coverage tools, merely as a complementary approach.

Jester is for Java code and JUnit tests. Pester is Jester for Python code and PyUnit tests Nester is a port of Jester for C#.

JVMDI Code Coverage Analyser
This small utility is a shared library which when loaded into a Java VM (1.4+) which supports JVMDI will record all the lines of code executed. This is a relatively coarse coverage method, but good enough for a lot of purposes.

GroboCodeCoverage
GroboCodeCoverage is a 100% Pure Java implementation of a Code Coverage tool. It uses Jakarta's BCEL platform to post-compile class files to add logging statements for tracking coverage. The CodeCoverage package contains a tool to help you discover what parts of your code have not executed during unit tests.

jcoverage/gpl
jcoverage/gpl is a free code-coverage tool for Java programmers that allows them to measure the effectiveness of their Java tests and how much of a software program's code has been tested. jcoverage/gpl identifies how many times each line of code in your application has been executed and you can see which parts of your software remain untested. After instrumenting your code and running your tests, a report is generated allowing you to view information coverage figures from a project level right down to the individual line of code. This process is called 'code coverage'.

jcoverage have a suite of tools and technologies designed to improve your coverage and testing productivity. The aim is to reduce the 'code - test - diagnose - fix' cycle. jcoverage enables software projects to save time, money and effort by allowing programmers to monitor progress, catch defects and improve quality.

Everybody wants to make the practice of coding more efficient. However, the reality is that your productivity is inextricably linked with how efficiently each step of the development cycle is performed. Beyond just productivity in coding, there are the knotty tasks of running tests, gathering results, diagnosing failures. Each step has the potential to eat into your development time.

With jcoverage you can:

• measure the percentage of code that has been tested
  
• run your tests, create your reports, immediately get all information about problems in your system - with data shown on a per-test basis.
  The difference with jcoverage is that it works by modifying your Java at the bytecode level. It also works against code that you do not have source code for.
  

JBlanket
JBlanket is a tool for assessing and improving method coverage of unit test cases. It is integrated with JUnit and Ant.

Cobertura
Cobertura is a free Java tool that calculates the percentage of code accessed by tests. It can be used to identify which parts of your Java program are lacking test coverage. It is based on jcoverage. Cobertura produces very nice reports. It works by instrumenting Java bytecode after it has been compiled.

• Can be executed from ant or from the command line.
  
• Instruments Java bytecode after it has been compiled.
  
• Can generate reports in HTML or XML.
  
• Shows the percentage of lines and branches covered for each class, each package, and for the overall project.
  
• Shows the McCabe cyclomatic code complexity of each class, and the average cyclomatic code complexity for each package, and for the overall product.
  
• Can sort HTML results by class name, percent of lines covered, percent of branches covered, etc. And can sort in ascending or decending order.

Coverlipse
An eclipse plugin for code coverage visualization of JUnit Tests. Supported coverages include block coverage and all-uses coverage (Data Flow Analysis).

Coverlipse is an Eclipse plugin that visualizes the code coverage of JUnit Tests. It is unique for it integrates seamlessly in Eclipse. The coverage results are given directly after a JUnit run. This makes it the perfect tool for developers to recognize their tests fullfil their task. Its features are:

• All Uses Coverage
  
• Block Coverage (also known as Statement Coverage)
  
• Branch Coverage (Not so soon to come)
  
• Just one test run is needed for evaluation of all coverage criterias
  
• No configuration methods to learn - the configuration is done the same way as normal JUnit runs in Eclipse.
  
• Easy way to include/exclude packages from the test
  
• Direct feedback in the Eclipse Java Editor
  
• Explanation of the results in specialized views

License is CPL (Common Public License)

DMOZ entries for Java Debugging

API Tracer Level One - Trap functions in DLL under Windows NT/2000/XP. Trapping engine is not limited in trapping DLL exports only and can trap any function, which address will be passed to it. [Freeware]

Auto Debug System - An auto-tracing tool to spy Window API and COM Interface calls.

Coretrace - A tool for analysing core files from crashed applications compiled by GCC. Runs on x86, PowerPC and Etrax (cris) Linux and compatiable systems. [Open source, GPL]

DDD - Data Display Debugger - A graphical X Window front-end for command-line debuggers such as GDB, DBX, WDB, Ladebug, JDB, XDB, the Perl debugger, or the Python debugger.

Etnus - Debugging Tools - Developer of Totalview, a tool which aids in the development of multithreaded, multiprocess and network-distributed applications.

Fx2 - Debugger for Fortran, C, C++, assembler. It can work with compilers from multiple vendors. By ABSOFT Corporation. [Commercial]

GDB: The GNU Debugger - Allows debug programs written in C, C++, and other languages, by executing them in a controlled fashion, and printing their data, on a wide variety of UNIX and non-UNIX systems.

The GNU Visual Debugger (GVD) - Written in Ada as a front end to GDB and other debug programs.

HP WDB Debugger - An HP-supported implementation of the GNU GDB debugger.

Labit - LabitStudio is a tool that helps you to analyze the reason of the exception in your application. It helps you to find the reason of the application failure without asking the user a great number of questions. Labit Disassembler is a library which allows you to disassemble binary code from memory or a file. DumpAnalyser is a free distributable instrument to create reports from dmp-files at this moment it supports creating reports in HTML format.

Microsoft Debugging Tools - Downloads and related resources for debugging tools for Windows.

Sankhya Tools for Software Development - Sankhya Simulator, a retargetable Instruction Set Simulator that loads ELF/DWARF and S-Record Files; Sankhya Debugger, a simple assembly level system debugger.

SmartInspect - A logging tool for debugging and monitoring .NET, Java and Delphi applications. [Commercial, free personal edition for non-commercial use]

Team Remote Debugger 2001 - A tool that allows an individual or team to trace and debug any number of code units which may reside on multiple shared and dedicated servers at the same time. Supports ASP,VB,VC,VJ,T-SQL,Delphi,CFML.

See also Java Open Source Code Coverage Tools -Non code Coverage Java Tools from Java-source