MCP Java Testing Agent

This repository provides an MCP (Model Context Protocol) server that exposes tools to automate test generation, coverage analysis, and style checking for Java/Maven projects. It is designed to be driven by an MCP-aware client using the tester.prompt.md prompt.

Overview

The MCP server (in main.py) exposes tools that:

• Discover public methods in a Java codebase

• Generate skeleton JUnit tests

• Run Maven (mvn clean test)

• Analyze JaCoCo coverage reports

• Analyze Checkstyle reports

The higher-level loop (iterating until coverage/style goals are met) is described in tester.prompt.md and executed by the LLM client, not hard-coded in Python.

Requirements

• Python 3.x

• Java JDK installed and on PATH

• Maven (mvn) installed and on PATH

• Maven project configured to:

  • Place sources under something like A2/src/main/java

  • Generate JaCoCo XML at A2/target/site/jacoco/jacoco.xml

  • Generate Checkstyle XML at A2/target/checkstyle-result.xml

• An MCP-capable editor/client (e.g., VS Code with MCP integration)

Installation & Configuration

1. Clone and install:

   git clone <your-repo-url>
   cd <your-repo-folder>
   pip install fastmcp
   
    Verify:
   
    java -version
    mvn -v
   
    Ensure your Maven pom.xml is set up to:
   
        Run tests
   
        Produce JaCoCo and Checkstyle reports at the paths above

Running the MCP Server

From the project root:

python server.py

This starts the MCP server over SSE:

if name == "main": mcp.run(transport="sse")

Your MCP client should be configured to connect to this server. Using the tester Prompt

Assuming you’re in an editor like VS Code with MCP enabled:

Open the project folder (containing main.py and tester.prompt.md).

Open tester.prompt.md (or tester.md) in the editor.

Press Ctrl+Shift+P to open the Command Palette.

Select “Run Prompt” (or the equivalent command).

Choose the tester prompt.

The MCP client will then:

Call the tools defined in tester.prompt.md:

- mcp-final/generate-tests
- mcp-final/run_tests
- mcp-final/analyze-coverage
- mcp-final/get_all_public_methods
- mcp-final/analyze-checkstyle
- mcp-final/run-checkstyle
- mcp-final/git-add-all
- mcp-final/git-commit
- mcp-final/git_pull_request
- mcp-final/git_push
- mcp-final/git_status

Iterate to generate tests, run coverage/style checks, and produce a final summary.

Project Structure (Typical)

├── main.py # MCP server and tools ├── .github/prompts/ │ └── tester.prompt.md # Agent configuration/prompt ├── A2/ │ ├── pom.xml │ ├── src/main/java/... # Java sources │ └── target/ │ ├── site/jacoco/jacoco.xml │ └── checkstyle-result.xml

Adjust paths as needed; defaults are used in the tool implementations. MCP Tools generate_tests(source_file: str) -> str

Generate a skeleton JUnit test class for a given .java file.

Extracts the class name and public method names via regex.

Creates {ClassName}Test with stub methods:

@Test
void test_methodName() {
    // TODO: implement test
}

Writes to: codebase/src/test/java/{ClassName}Test.java.

Returns: Path message on success, or an error string if the file/class/methods can’t be found. get_all_public_methods(dir: str = "A2/src/main/java") -> List[str]

Recursively scan dir for .java files and return all lines starting with public.

Uses os.walk to find .java files.

Reads each file line-by-line and keeps line.strip().startswith("public").

Returns: List of raw lines (method signatures, constructors, or public fields). analyze_coverage(xml_path: str = "A2/target/site/jacoco/jacoco.xml") -> dict

Parse a JaCoCo XML report and list methods with <100% instruction coverage.

Output structure:

{ "uncovered_methods": [ { "class": "com/example/MyClass", "method": "myMethod", "coverage": 0.75, "missed": 10, "covered": 30 }, ... ], "count": 3 }

Returns an "error" key if the XML file is missing. run_checkstyle() -> str

Run the Maven build and tests:

mvn clean test

Assumes your Maven config runs Checkstyle and JaCoCo as part of the build.

Returns: stdout from the Maven process (errors are visible in this text). analyze_checkstyle(xml_path: str = "A2/target/checkstyle-result.xml") -> dict

Parse a Checkstyle XML report and list all style violations.

Output structure:

{ "violations": [ { "file": "/path/to/Foo.java", "line": "42", "column": "13", "severity": "warning", "message": "Line is longer than 100 characters", "source": "com.puppycrawl.tools.checkstyle.checks.sizes.LineLengthCheck" }, ... ], "count": 5 }

Returns an "error" key if the XML file is missing. Agent Workflow Summary

A typical workflow implemented in tester.prompt.md:

Call get_all_public_methods to discover public methods.

Call generate_tests to create initial JUnit tests.

Call run_checkstyle to run mvn clean test and produce JaCoCo + Checkstyle reports.

Call analyze_coverage to find uncovered methods.

Call analyze_checkstyle to find style violations.

Update tests and code (by the agent using file edits), then repeat steps 3–5.

Stop when:

    100% coverage and zero Checkstyle issues are reached, or

    A maximum iteration count (e.g., 10) is reached.

Produce a final summary report (tests created, coverage, style status, recommendations).

Notes & Limitations

Regex-based parsing is simple and may not handle all Java edge cases (complex generics, annotations, inner classes).

Default paths (A2/src/main/java, codebase/src/test/java, etc.) can be customized; keep tool defaults in sync with your project layout.

run_checkstyle only runs mvn clean test; ensure your pom.xml actually binds JaCoCo and Checkstyle to this phase.

The iterative “improve coverage & style” loop is implemented by the MCP client/LLM using these tools, not within server.py itself.