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Cover MCP now doing Python too #5

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51 changes: 35 additions & 16 deletions covermcp/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,11 @@

This module provides a FastMCP server that exposes Diffblue Cover's test generation
capabilities through the Model Context Protocol. It allows LLMs to invoke Diffblue Cover
to automatically generate unit tests for Java projects.
to automatically generate unit tests for Java and Python projects.

The server exposes a 'create' tool that wraps the dcover CLI, providing configurable
test generation with options for fuzzing, verification, and batch processing.
test generation with options for fuzzing, verification, and batch processing. Additional
tools 'refactor' and 'issues' are available for Java projects only.

Environment Variables:
DIFFBLUE_COVER_CLI: Path to the dcover executable (optional if dcover is on PATH)
Expand Down Expand Up @@ -75,9 +76,9 @@

@mcp.prompt("write tests")
def write_tests() -> list[dict]:
"""Provide system prompt for Java unit test writing guidance.
"""Provide system prompt for Java and Python unit test writing guidance.

Establishes LLM context as a Java unit testing expert to improve
Establishes LLM context as a unit testing expert to improve
test generation quality and suggestions.

Returns:
Expand All @@ -86,7 +87,7 @@ def write_tests() -> list[dict]:
return [
{
"role": "system",
"content": "You are a helpful assistant highly skilled at writing unit tests for java code.",
"content": "You are a helpful assistant highly skilled at writing unit tests for Java and Python code.",
},
]

Expand All @@ -113,6 +114,10 @@ def create_options() -> dict:
for efficient caching.
"""
return {
"--agent": "Select AI agent for test generation: NONE, CLAUDE, CODEX, COPILOT. When using an agent, tests are "
"generated method-by-method with git commit checkpointing. It is recommended to use this "
"option where available as it improves test quality. Set the agent to match the LLM platform "
"in use, e.g. when running in Claude Code, use '--agent=claude'. Default: NONE",
"--active-profiles": "The comma separated list of profiles to use where creating Spring tests. Not providing a "
"value will use the default profile.",
"--allow-jni": "The comma separated list of additional JNI library name prefixes that should be usable within "
Expand Down Expand Up @@ -379,23 +384,27 @@ async def create( # noqa: PLR0913,PLR0917
args: Annotated[list[str] | None, "The options to pass to dcover"] = None,
ctx: Annotated[Context | None, "The MCP Server Context"] = None,
) -> object:
"""Invoke Diffblue Cover to generate unit tests for Java code.
"""Invoke Diffblue Cover to generate unit tests for Java or Python code.

This tool executes the dcover CLI to automatically generate JUnit tests for the
specified Java classes, methods, or packages. It supports various configuration
options to control the test generation process.
This tool executes the dcover CLI to automatically generate tests for the
specified classes, methods, packages, or modules. For Java projects, it generates
JUnit tests. For Python projects (experimental), pass "--python" in the args parameter
to generate pytest tests. It supports various configuration options to control the
test generation process.

Args:
path: Path to the dcover executable. If not provided, searches system PATH
and the DIFFBLUE_COVER_CLI environment variable.
working_directory: Root directory of the Java project to test. Defaults to
working_directory: Root directory of the project to test. Defaults to
the current working directory.
dcover_timeout: Maximum execution time in seconds. Defaults to 600. Set to None
for no timeout (not recommended).
entry_points: List of fully-qualified Java targets (packages, classes, or methods)
to generate tests for. Examples: ['com.example.MyClass',
'com.example.MyClass.myMethod']. If None, tests entire project.
args: Additional arguments to pass to dcover. Defaults to None.
entry_points: List of fully-qualified targets (packages, classes, or methods)
to generate tests for. For Java: ['com.example.MyClass',
'com.example.MyClass.myMethod']. For Python: ['mymodule', 'mymodule.MyClass'].
If None, tests entire project.
args: Additional arguments to pass to dcover. For Python projects, include "--python".
Defaults to None.
ctx: MCP server context for logging and progress reporting (auto-injected by FastMCP).

Returns:
Expand All @@ -411,6 +420,12 @@ async def create( # noqa: PLR0913,PLR0917
The error includes the partial output collected before failure.

Note:
For enhanced test generation using LLMs, pass "--agent=claude" (or "codex", "copilot")
in the args parameter. This uses the specified LLM agent for test generation instead of
the internal non-LLM engine. It is recommended to use this option where available as it
improves test quality. If used, set the agent to the same type as yourself, e.g. when
running in Claude Code, use "--agent=claude".

If DIFFBLUE_COVER_OPTIONS environment variable is set, it overrides all
option parameters (batch, skip_verification, etc.) except path, working_directory,
timeout, and entry_points.
Expand Down Expand Up @@ -478,11 +493,13 @@ async def refactor( # noqa: PLR0913,PLR0917
args: Annotated[list[str] | None, "The additional options to pass to dcover refactor"] = None,
ctx: Annotated[Context | None, "The MCP Server Context"] = None,
) -> object:
"""Invoke Diffblue Cover to refactor the project (aliased as 'fix-build').
"""Invoke Diffblue Cover to refactor the Java project (aliased as 'fix-build').

This tool executes the `dcover refactor` command to apply automated
refactorings, such as fixing build issues or adding missing dependencies.

**Note:** This command is Java-only and does not support Python projects.

Args:
path: Path to the dcover executable. If not provided, searches system PATH
and the DIFFBLUE_COVER_CLI environment variable.
Expand Down Expand Up @@ -534,11 +551,13 @@ async def issues( # noqa: PLR0913,PLR0917
args: Annotated[list[str] | None, "The additional options to pass to dcover issues"] = None,
ctx: Annotated[Context | None, "The MCP Server Context"] = None,
) -> object:
"""Invoke Diffblue Cover to identify project issues.
"""Invoke Diffblue Cover to identify Java project issues.

This tool executes the `dcover issues` command to output a prioritized
list of project issues that may prevent test generation.

**Note:** This command is Java-only and does not support Python projects.

Args:
path: Path to the dcover executable. If not provided, searches system PATH
and the DIFFBLUE_COVER_CLI environment variable.
Expand Down