Maxros/test

CS4570 Java Refactoring Benchmark

A benchmark of Java refactoring commits mined from GitHub repositories, split into high-resource and low-resource tiers based on repository popularity. Built for the TU Delft CS4570 ML for Software Engineering course (2026).

Dataset split

Tier	Repositories	Instances	Star range
High-resource	57	618	1000-7298
Low-resource	~60	198	13-90
Total		816

Use the resource_tier field to filter by tier. repo_stars and repo_forks are included for fine-grained popularity analysis.

Construction

Each instance is a single-file refactoring commit that was:

1. Detected by RefactoringMiner 3.1.3 as containing at least one Java refactoring operation
2. Verified by building the project before and after the commit using Docker (Maven/Gradle, JDK 17/21)
3. Filtered to commits where the project compiles and tests pass both before and after (pure refactorings)

High-resource repos have >=1000 stars and >=10 contributors; low-resource repos have <100 stars.

Fields

Field	Type	Description
instance_id	string	Unique identifier
repo	string	owner/repo identifier
resource_tier	string	"high" or "low"
repo_stars	int or null	GitHub star count at collection time
repo_forks	int or null	GitHub fork count at collection time
language	string	Always "java"
base_commit	string	Parent commit SHA
merge_commit	string	Refactoring commit SHA
refactoring_types	list[str]	Refactoring type labels from RefactoringMiner
refactoring_descriptions	list[str] or null	Human-readable descriptions (HR only)
file_path	string	Java file path that was refactored
source_code_before	string	File content at base commit
source_code_after	string	File content at merge commit
diff	string	Unified diff between before and after
is_pure_refactoring	bool or null	True if only refactoring operations changed
compile_before	bool or null	Project compiled at base commit
compile_after	bool or null	Project compiled at merge commit
tests_pass_before	bool or null	All tests pass at base commit
tests_pass_after	bool or null	All tests pass at merge commit
FAIL_TO_PASS	list[str]	Tests failing before, passing after
PASS_TO_PASS	list[str]	Tests passing both before and after
created_at	string or null	Commit timestamp (ISO 8601)
repo_license	string or null	SPDX license identifier
lines_changed	int or null	Lines changed in the refactoring

Refactoring types

Top types across both tiers: Extract Method, Rename Method, Rename Variable, Rename Parameter, Extract Variable, Inline Variable, Change Variable Type, Add Parameter, Add Method Annotation, Rename Attribute.

66 unique refactoring types in total.

Usage

from datasets import load_dataset

ds = load_dataset("Maxros/test", split="test")

# Filter by tier
hr = ds.filter(lambda x: x["resource_tier"] == "high")
lr = ds.filter(lambda x: x["resource_tier"] == "low")

Citation

TU Delft CS4570 -- ML for Software Engineering benchmark, 2026.