add vitest runner

code_to_optimize/js/code_to_optimize_js/package-lock.json

@@ -14,15 +14,13 @@
       }
     },
     "../../../packages/codeflash": {
-      "version": "0.1.0",
+      "version": "0.3.1",
       "dev": true,
       "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {
         "@msgpack/msgpack": "^3.0.0",
-        "better-sqlite3": "^12.0.0",
-        "jest-junit": "^16.0.0",
-        "jest-runner": "^29.7.0"
+        "better-sqlite3": "^12.0.0"
       },
       "bin": {
         "codeflash": "bin/codeflash.js",
@@ -33,7 +31,8 @@
       },
       "peerDependencies": {
         "jest": ">=27.0.0",
-        "jest-runner": ">=27.0.0"
+        "jest-runner": ">=27.0.0",
+        "vitest": ">=1.0.0"
       },
       "peerDependenciesMeta": {
         "jest": {
@@ -41,6 +40,9 @@
         },
         "jest-runner": {
           "optional": true
+        },
+        "vitest": {
+          "optional": true
         }
       }
     },

code_to_optimize/js/code_to_optimize_js_cjs/package-lock.json

@@ -14,15 +14,13 @@
       }
     },
     "../../../packages/codeflash": {
-      "version": "0.2.0",
+      "version": "0.3.1",
       "dev": true,
       "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {
         "@msgpack/msgpack": "^3.0.0",
-        "better-sqlite3": "^12.0.0",
-        "jest-junit": "^16.0.0",
-        "jest-runner": "^29.7.0"
+        "better-sqlite3": "^12.0.0"
       },
       "bin": {
         "codeflash": "bin/codeflash.js",
@@ -33,7 +31,8 @@
       },
       "peerDependencies": {
         "jest": ">=27.0.0",
-        "jest-runner": ">=27.0.0"
+        "jest-runner": ">=27.0.0",
+        "vitest": ">=1.0.0"
       },
       "peerDependenciesMeta": {
         "jest": {
@@ -41,6 +40,9 @@
         },
         "jest-runner": {
           "optional": true
+        },
+        "vitest": {
+          "optional": true
         }
       }
     },

code_to_optimize/js/code_to_optimize_ts/package-lock.json

@@ -20,7 +20,7 @@
       }
     },
     "../../../packages/codeflash": {
-      "version": "0.1.0",
+      "version": "0.3.1",
       "dev": true,
       "hasInstallScript": true,
       "license": "MIT",
@@ -36,11 +36,19 @@
         "node": ">=18.0.0"
       },
       "peerDependencies": {
-        "jest": ">=27.0.0"
+        "jest": ">=27.0.0",
+        "jest-runner": ">=27.0.0",
+        "vitest": ">=1.0.0"
       },
       "peerDependenciesMeta": {
         "jest": {
           "optional": true
+        },
+        "jest-runner": {
+          "optional": true
+        },
+        "vitest": {
+          "optional": true
         }
       }
     },

code_to_optimize/js/code_to_optimize_vitest/package-lock.json

@@ -15,15 +15,13 @@
       }
     },
     "../../../packages/codeflash": {
-      "version": "0.3.0",
+      "version": "0.3.1",
       "dev": true,
       "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {
         "@msgpack/msgpack": "^3.0.0",
-        "better-sqlite3": "^12.0.0",
-        "jest-junit": "^16.0.0",
-        "jest-runner": "^29.7.0"
+        "better-sqlite3": "^12.0.0"
       },
       "bin": {
         "codeflash": "bin/codeflash.js",
@@ -34,7 +32,8 @@
       },
       "peerDependencies": {
         "jest": ">=27.0.0",
-        "jest-runner": ">=27.0.0"
+        "jest-runner": ">=27.0.0",
+        "vitest": ">=1.0.0"
       },
       "peerDependenciesMeta": {
         "jest": {
@@ -42,6 +41,9 @@
         },
         "jest-runner": {
           "optional": true
+        },
+        "vitest": {
+          "optional": true
         }
       }
     },

codeflash/cli_cmds/cli.py

@@ -12,6 +12,7 @@ from codeflash.cli_cmds.extension import install_vscode_extension
 from codeflash.code_utils import env_utils
 from codeflash.code_utils.code_utils import exit_with_message
 from codeflash.code_utils.config_parser import parse_config_file
+from codeflash.languages.test_framework import set_current_test_framework
 from codeflash.lsp.helpers import is_LSP_enabled
 from codeflash.version import __version__ as version
 
@@ -210,6 +211,11 @@ def process_pyproject_config(args: Namespace) -> Namespace:
     # For JS/TS projects, tests_root is optional (Jest auto-discovers tests)
     # Default to module_root if not specified
     is_js_ts_project = pyproject_config.get("language") in ("javascript", "typescript")
+
+    # Set the test framework singleton for JS/TS projects
+    if is_js_ts_project and pyproject_config.get("test_runner"):
+        set_current_test_framework(pyproject_config["test_runner"])
+
     if args.tests_root is None:
         if is_js_ts_project:
             # Try common JS test directories, or default to module_root

codeflash/languages/__init__.py

@@ -48,9 +48,19 @@ from codeflash.languages.registry import (
     get_supported_languages,
     register_language,
 )
+from codeflash.languages.test_framework import (
+    current_test_framework,
+    get_js_test_framework_or_default,
+    is_jest,
+    is_mocha,
+    is_pytest,
+    is_unittest,
+    is_vitest,
+    reset_test_framework,
+    set_current_test_framework,
+)
 
 __all__ = [
-    # Base types
     "CodeContext",
     "FunctionInfo",
     "HelperFunction",
@@ -59,18 +69,25 @@ __all__ = [
     "ParentInfo",
     "TestInfo",
     "TestResult",
-    # Current language singleton
     "current_language",
     "current_language_support",
-    # Registry functions
+    "current_test_framework",
     "detect_project_language",
+    "get_js_test_framework_or_default",
     "get_language_support",
     "get_supported_extensions",
     "get_supported_languages",
     "is_javascript",
+    "is_jest",
+    "is_mocha",
+    "is_pytest",
     "is_python",
     "is_typescript",
+    "is_unittest",
+    "is_vitest",
     "register_language",
     "reset_current_language",
+    "reset_test_framework",
     "set_current_language",
+    "set_current_test_framework",
 ]

codeflash/languages/javascript/support.py

@@ -1925,7 +1925,7 @@ class JavaScriptSupport:
         project_root: Path | None = None,
         enable_coverage: bool = False,
         candidate_index: int = 0,
-        test_framework: str = "jest",
+        test_framework: str | None = None,
     ) -> tuple[Path, Any, Path | None, Path | None]:
         """Run behavioral tests using the detected test framework.
 
@@ -1937,13 +1937,17 @@ class JavaScriptSupport:
             project_root: Project root directory.
             enable_coverage: Whether to collect coverage information.
             candidate_index: Index of the candidate being tested.
-            test_framework: Test framework to use ("jest" or "vitest").
+            test_framework: Test framework to use ("jest" or "vitest"). If None, uses singleton.
 
         Returns:
             Tuple of (result_file_path, subprocess_result, coverage_path, config_path).
 
         """
-        if test_framework == "vitest":
+        from codeflash.languages.test_framework import get_js_test_framework_or_default
+
+        framework = test_framework or get_js_test_framework_or_default()
+
+        if framework == "vitest":
             from codeflash.languages.javascript.vitest_runner import run_vitest_behavioral_tests
 
             return run_vitest_behavioral_tests(
@@ -1978,7 +1982,7 @@ class JavaScriptSupport:
         min_loops: int = 5,
         max_loops: int = 100_000,
         target_duration_seconds: float = 10.0,
-        test_framework: str = "jest",
+        test_framework: str | None = None,
     ) -> tuple[Path, Any]:
         """Run benchmarking tests using the detected test framework.
 
@@ -1991,13 +1995,17 @@ class JavaScriptSupport:
             min_loops: Minimum number of loops for benchmarking.
             max_loops: Maximum number of loops for benchmarking.
             target_duration_seconds: Target duration for benchmarking in seconds.
-            test_framework: Test framework to use ("jest" or "vitest").
+            test_framework: Test framework to use ("jest" or "vitest"). If None, uses singleton.
 
         Returns:
             Tuple of (result_file_path, subprocess_result).
 
         """
-        if test_framework == "vitest":
+        from codeflash.languages.test_framework import get_js_test_framework_or_default
+
+        framework = test_framework or get_js_test_framework_or_default()
+
+        if framework == "vitest":
             from codeflash.languages.javascript.vitest_runner import run_vitest_benchmarking_tests
 
             return run_vitest_benchmarking_tests(
@@ -2032,7 +2040,7 @@ class JavaScriptSupport:
         timeout: int | None = None,
         project_root: Path | None = None,
         line_profile_output_file: Path | None = None,
-        test_framework: str = "jest",
+        test_framework: str | None = None,
     ) -> tuple[Path, Any]:
         """Run tests for line profiling using the detected test framework.
 
@@ -2043,13 +2051,17 @@ class JavaScriptSupport:
             timeout: Optional timeout in seconds.
             project_root: Project root directory.
             line_profile_output_file: Path where line profile results will be written.
-            test_framework: Test framework to use ("jest" or "vitest").
+            test_framework: Test framework to use ("jest" or "vitest"). If None, uses singleton.
 
         Returns:
             Tuple of (result_file_path, subprocess_result).
 
         """
-        if test_framework == "vitest":
+        from codeflash.languages.test_framework import get_js_test_framework_or_default
+
+        framework = test_framework or get_js_test_framework_or_default()
+
+        if framework == "vitest":
             from codeflash.languages.javascript.vitest_runner import run_vitest_line_profile_tests
 
             return run_vitest_line_profile_tests(

codeflash/languages/javascript/vitest_runner.py

@@ -51,6 +51,22 @@ def _find_vitest_project_root(file_path: Path) -> Path | None:
     return None
 
 
+def _is_vitest_coverage_available(project_root: Path) -> bool:
+    """Check if Vitest coverage package is available.
+
+    Args:
+        project_root: The project root directory.
+
+    Returns:
+        True if @vitest/coverage-v8 or @vitest/coverage-istanbul is installed.
+
+    """
+    node_modules = project_root / "node_modules"
+    return (node_modules / "@vitest" / "coverage-v8").exists() or (
+        node_modules / "@vitest" / "coverage-istanbul"
+    ).exists()
+
+
 def _ensure_runtime_files(project_root: Path) -> None:
     """Ensure JavaScript runtime package is installed in the project.
 
@@ -217,15 +233,19 @@ def run_vitest_behavioral_tests(
     # Ensure the codeflash npm package is installed
     _ensure_runtime_files(effective_cwd)
 
-    # Coverage output directory
+    # Coverage output directory - only enable if coverage package is available
     coverage_dir = get_run_tmp_file(Path("vitest_coverage"))
-    coverage_json_path = coverage_dir / "coverage-final.json" if enable_coverage else None
+    coverage_available = _is_vitest_coverage_available(effective_cwd) if enable_coverage else False
+    coverage_json_path = coverage_dir / "coverage-final.json" if coverage_available else None
+
+    if enable_coverage and not coverage_available:
+        logger.debug("Vitest coverage package not installed, running without coverage")
 
     # Build Vitest command
     vitest_cmd = _build_vitest_behavioral_command(test_files=test_files, timeout=timeout, output_file=result_file_path)
 
-    # Add coverage flags if enabled
-    if enable_coverage:
+    # Add coverage flags only if coverage is available
+    if coverage_available:
         vitest_cmd.extend(["--coverage", "--coverage.reporter=json", f"--coverage.reportsDirectory={coverage_dir}"])
 
     # Set up environment

codeflash/languages/test_framework.py

@@ -0,0 +1,145 @@
+"""Singleton for the current test framework being used in the codeflash session.
+
+This module provides a centralized way to access and set the current test framework
+throughout the codeflash codebase, similar to how the language singleton works.
+
+For JavaScript/TypeScript projects, this determines whether to use Jest or Vitest
+for test execution.
+
+Usage:
+    from codeflash.languages.test_framework import (
+        current_test_framework,
+        set_current_test_framework,
+        is_jest,
+        is_vitest,
+    )
+
+    # Set the test framework at the start of a session (auto-detected from package.json)
+    set_current_test_framework("vitest")
+
+    # Check the current test framework anywhere in the codebase
+    if is_vitest():
+        # Vitest-specific code
+        ...
+
+    # Get the current test framework
+    framework = current_test_framework()
+"""
+
+from __future__ import annotations
+
+from typing import Literal
+
+TestFramework = Literal["jest", "vitest", "mocha", "pytest", "unittest"]
+
+# Module-level singleton for the current test framework
+_current_test_framework: TestFramework | None = None
+
+
+def current_test_framework() -> TestFramework | None:
+    """Get the current test framework being used in this codeflash session.
+
+    Returns:
+        The current test framework string, or None if not set.
+
+    """
+    return _current_test_framework
+
+
+def set_current_test_framework(framework: TestFramework | str | None) -> None:
+    """Set the current test framework for this codeflash session.
+
+    This should be called once at the start of an optimization run,
+    typically after reading the project configuration.
+
+    Args:
+        framework: Test framework name ("jest", "vitest", "mocha", "pytest", "unittest").
+
+    """
+    global _current_test_framework
+
+    if _current_test_framework is not None:
+        return
+
+    if framework is not None:
+        framework = framework.lower()
+        if framework not in ("jest", "vitest", "mocha", "pytest", "unittest"):
+            # Default to jest for unknown JS frameworks, pytest for unknown Python
+            from codeflash.languages.current import is_javascript
+
+            framework = "jest" if is_javascript() else "pytest"
+
+    _current_test_framework = framework
+
+
+def reset_test_framework() -> None:
+    """Reset the current test framework to None.
+
+    Useful for testing or when starting a new session.
+    """
+    global _current_test_framework
+    _current_test_framework = None
+
+
+def is_jest() -> bool:
+    """Check if the current test framework is Jest.
+
+    Returns:
+        True if the current test framework is Jest.
+
+    """
+    return _current_test_framework == "jest"
+
+
+def is_vitest() -> bool:
+    """Check if the current test framework is Vitest.
+
+    Returns:
+        True if the current test framework is Vitest.
+
+    """
+    return _current_test_framework == "vitest"
+
+
+def is_mocha() -> bool:
+    """Check if the current test framework is Mocha.
+
+    Returns:
+        True if the current test framework is Mocha.
+
+    """
+    return _current_test_framework == "mocha"
+
+
+def is_pytest() -> bool:
+    """Check if the current test framework is pytest.
+
+    Returns:
+        True if the current test framework is pytest.
+
+    """
+    return _current_test_framework == "pytest"
+
+
+def is_unittest() -> bool:
+    """Check if the current test framework is unittest.
+
+    Returns:
+        True if the current test framework is unittest.
+
+    """
+    return _current_test_framework == "unittest"
+
+
+def get_js_test_framework_or_default() -> TestFramework:
+    """Get the current test framework for JS/TS, defaulting to 'jest' if not set.
+
+    This is a convenience function for JS/TS code that needs a framework.
+
+    Returns:
+        The current test framework, or 'jest' as default.
+
+    """
+    if _current_test_framework in ("jest", "vitest", "mocha"):
+        return _current_test_framework
+    return "jest"

packages/codeflash/package.json

@@ -1,6 +1,6 @@
 {
   "name": "codeflash",
-  "version": "0.3.0",
+  "version": "0.3.1",
   "description": "Codeflash - AI-powered code optimization for JavaScript and TypeScript",
   "main": "runtime/index.js",
   "types": "runtime/index.d.ts",
@@ -9,7 +9,7 @@
     "codeflash-setup": "./bin/codeflash-setup.js"
   },
   "publishConfig": {
-  "access": "public"
+    "access": "public"
   },
   "exports": {
     ".": {
@@ -52,7 +52,8 @@
     "typescript",
     "ai",
     "cli",
-    "jest"
+    "jest",
+    "vitest"
   ],
   "author": "Codeflash AI",
   "license": "MIT",
@@ -70,7 +71,8 @@
   },
   "peerDependencies": {
     "jest": ">=27.0.0",
-    "jest-runner": ">=27.0.0"
+    "jest-runner": ">=27.0.0",
+    "vitest": ">=1.0.0"
   },
   "peerDependenciesMeta": {
     "jest": {
@@ -78,12 +80,13 @@
     },
     "jest-runner": {
       "optional": true
+    },
+    "vitest": {
+      "optional": true
     }
   },
   "dependencies": {
     "better-sqlite3": "^12.0.0",
-    "@msgpack/msgpack": "^3.0.0",
-    "jest-runner": "^29.7.0",
-    "jest-junit": "^16.0.0"
+    "@msgpack/msgpack": "^3.0.0"
   }
 }

packages/codeflash/runtime/loop-runner.js

@@ -20,6 +20,10 @@
  *
  * Usage:
  *   npx jest --runner=codeflash/loop-runner
+ *
+ * NOTE: This runner requires jest-runner to be installed in your project.
+ *       It is a Jest-specific feature and does not work with Vitest.
+ *       For Vitest projects, external looping is handled by the Python runner.
  */
 
 'use strict';
@@ -27,9 +31,20 @@
 const { createRequire } = require('module');
 const path = require('path');
 
-const jestRunnerPath = require.resolve('jest-runner');
-const internalRequire = createRequire(jestRunnerPath);
-const runTest = internalRequire('./runTest').default;
+// Try to load jest-runner - it's a peer dependency that must be installed by the user
+let runTest;
+let jestRunnerAvailable = false;
+
+try {
+    const jestRunnerPath = require.resolve('jest-runner');
+    const internalRequire = createRequire(jestRunnerPath);
+    runTest = internalRequire('./runTest').default;
+    jestRunnerAvailable = true;
+} catch (e) {
+    // jest-runner not installed - this is expected for Vitest projects
+    // The runner will throw a helpful error if someone tries to use it without jest-runner
+    jestRunnerAvailable = false;
+}
 
 // Configuration
 const MAX_BATCHES = parseInt(process.env.CODEFLASH_PERF_LOOP_COUNT || '10000', 10);
@@ -90,6 +105,14 @@ function deepCopy(obj, seen = new WeakMap()) {
  */
 class CodeflashLoopRunner {
     constructor(globalConfig, context) {
+        if (!jestRunnerAvailable) {
+            throw new Error(
+                'codeflash/loop-runner requires jest-runner to be installed.\n' +
+                'Please install it: npm install --save-dev jest-runner\n\n' +
+                'If you are using Vitest, the loop-runner is not needed - ' +
+                'Vitest projects use external looping handled by the Python runner.'
+            );
+        }
         this._globalConfig = globalConfig;
         this._context = context || {};
         this._eventEmitter = new SimpleEventEmitter();

tests/languages/javascript/test_support_dispatch.py

@@ -2,7 +2,7 @@
 
 These tests verify that run_behavioral_tests, run_benchmarking_tests, and
 run_line_profile_tests correctly dispatch to Jest or Vitest based on the
-test_framework parameter.
+test_framework parameter or singleton.
 """
 
 from __future__ import annotations
@@ -13,6 +13,7 @@ from unittest.mock import MagicMock, patch
 import pytest
 
 from codeflash.languages.javascript.support import JavaScriptSupport, TypeScriptSupport
+from codeflash.languages.test_framework import reset_test_framework, set_current_test_framework
 
 
 @pytest.fixture
@@ -27,6 +28,14 @@ def ts_support() -> TypeScriptSupport:
     return TypeScriptSupport()
 
 
+@pytest.fixture(autouse=True)
+def reset_singleton() -> None:
+    """Reset the test framework singleton before each test."""
+    reset_test_framework()
+    yield
+    reset_test_framework()
+
+
 @pytest.fixture
 def mock_test_paths() -> MagicMock:
     """Create a mock TestFiles object."""
@@ -43,87 +52,54 @@ class TestBehavioralTestsDispatch:
 
     @patch("codeflash.languages.javascript.test_runner.run_jest_behavioral_tests")
     def test_dispatches_to_jest_by_default(
-        self,
-        mock_jest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_jest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should dispatch to Jest when test_framework is not specified."""
         mock_jest_runner.return_value = (tmp_path / "result.xml", MagicMock(), None, None)
         (tmp_path / "package.json").write_text('{"name": "test"}')
 
-        js_support.run_behavioral_tests(
-            test_paths=mock_test_paths,
-            test_env={},
-            cwd=tmp_path,
-            project_root=tmp_path,
-        )
+        js_support.run_behavioral_tests(test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path)
 
         mock_jest_runner.assert_called_once()
 
     @patch("codeflash.languages.javascript.test_runner.run_jest_behavioral_tests")
     def test_dispatches_to_jest_explicitly(
-        self,
-        mock_jest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_jest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should dispatch to Jest when test_framework='jest'."""
         mock_jest_runner.return_value = (tmp_path / "result.xml", MagicMock(), None, None)
         (tmp_path / "package.json").write_text('{"name": "test"}')
 
         js_support.run_behavioral_tests(
-            test_paths=mock_test_paths,
-            test_env={},
-            cwd=tmp_path,
-            project_root=tmp_path,
-            test_framework="jest",
+            test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path, test_framework="jest"
         )
 
         mock_jest_runner.assert_called_once()
 
     @patch("codeflash.languages.javascript.vitest_runner.run_vitest_behavioral_tests")
     def test_dispatches_to_vitest(
-        self,
-        mock_vitest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_vitest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should dispatch to Vitest when test_framework='vitest'."""
         mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock(), None, None)
         (tmp_path / "package.json").write_text('{"name": "test"}')
 
         js_support.run_behavioral_tests(
-            test_paths=mock_test_paths,
-            test_env={},
-            cwd=tmp_path,
-            project_root=tmp_path,
-            test_framework="vitest",
+            test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path, test_framework="vitest"
         )
 
         mock_vitest_runner.assert_called_once()
 
     @patch("codeflash.languages.javascript.vitest_runner.run_vitest_behavioral_tests")
     def test_typescript_support_dispatches_to_vitest(
-        self,
-        mock_vitest_runner: MagicMock,
-        ts_support: TypeScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_vitest_runner: MagicMock, ts_support: TypeScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """TypeScriptSupport should also dispatch to Vitest when test_framework='vitest'."""
         mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock(), None, None)
         (tmp_path / "package.json").write_text('{"name": "test"}')
 
         ts_support.run_behavioral_tests(
-            test_paths=mock_test_paths,
-            test_env={},
-            cwd=tmp_path,
-            project_root=tmp_path,
-            test_framework="vitest",
+            test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path, test_framework="vitest"
         )
 
         mock_vitest_runner.assert_called_once()
@@ -134,54 +110,33 @@ class TestBenchmarkingTestsDispatch:
 
     @patch("codeflash.languages.javascript.test_runner.run_jest_benchmarking_tests")
     def test_dispatches_to_jest_by_default(
-        self,
-        mock_jest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_jest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should dispatch to Jest when test_framework is not specified."""
         mock_jest_runner.return_value = (tmp_path / "result.xml", MagicMock())
         (tmp_path / "package.json").write_text('{"name": "test"}')
 
-        js_support.run_benchmarking_tests(
-            test_paths=mock_test_paths,
-            test_env={},
-            cwd=tmp_path,
-            project_root=tmp_path,
-        )
+        js_support.run_benchmarking_tests(test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path)
 
         mock_jest_runner.assert_called_once()
 
     @patch("codeflash.languages.javascript.vitest_runner.run_vitest_benchmarking_tests")
     def test_dispatches_to_vitest(
-        self,
-        mock_vitest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_vitest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should dispatch to Vitest when test_framework='vitest'."""
         mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock())
         (tmp_path / "package.json").write_text('{"name": "test"}')
 
         js_support.run_benchmarking_tests(
-            test_paths=mock_test_paths,
-            test_env={},
-            cwd=tmp_path,
-            project_root=tmp_path,
-            test_framework="vitest",
+            test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path, test_framework="vitest"
         )
 
         mock_vitest_runner.assert_called_once()
 
     @patch("codeflash.languages.javascript.vitest_runner.run_vitest_benchmarking_tests")
     def test_passes_loop_parameters(
-        self,
-        mock_vitest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_vitest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should pass loop parameters to Vitest runner."""
         mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock())
@@ -209,54 +164,33 @@ class TestLineProfileTestsDispatch:
 
     @patch("codeflash.languages.javascript.test_runner.run_jest_line_profile_tests")
     def test_dispatches_to_jest_by_default(
-        self,
-        mock_jest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_jest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should dispatch to Jest when test_framework is not specified."""
         mock_jest_runner.return_value = (tmp_path / "result.xml", MagicMock())
         (tmp_path / "package.json").write_text('{"name": "test"}')
 
-        js_support.run_line_profile_tests(
-            test_paths=mock_test_paths,
-            test_env={},
-            cwd=tmp_path,
-            project_root=tmp_path,
-        )
+        js_support.run_line_profile_tests(test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path)
 
         mock_jest_runner.assert_called_once()
 
     @patch("codeflash.languages.javascript.vitest_runner.run_vitest_line_profile_tests")
     def test_dispatches_to_vitest(
-        self,
-        mock_vitest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_vitest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should dispatch to Vitest when test_framework='vitest'."""
         mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock())
         (tmp_path / "package.json").write_text('{"name": "test"}')
 
         js_support.run_line_profile_tests(
-            test_paths=mock_test_paths,
-            test_env={},
-            cwd=tmp_path,
-            project_root=tmp_path,
-            test_framework="vitest",
+            test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path, test_framework="vitest"
         )
 
         mock_vitest_runner.assert_called_once()
 
     @patch("codeflash.languages.javascript.vitest_runner.run_vitest_line_profile_tests")
     def test_passes_line_profile_output_file(
-        self,
-        mock_vitest_runner: MagicMock,
-        js_support: JavaScriptSupport,
-        mock_test_paths: MagicMock,
-        tmp_path: Path,
+        self, mock_vitest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
     ) -> None:
         """Should pass line_profile_output_file to Vitest runner."""
         mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock())
@@ -286,3 +220,121 @@ class TestTestFrameworkProperty:
     def test_typescript_default_framework_is_jest(self, ts_support: TypeScriptSupport) -> None:
         """TypeScriptSupport should have Jest as default test framework."""
         assert ts_support.test_framework == "jest"
+
+
+class TestTestFrameworkSingleton:
+    """Tests for test_framework singleton behavior."""
+
+    @patch("codeflash.languages.javascript.vitest_runner.run_vitest_behavioral_tests")
+    def test_uses_singleton_when_param_not_provided(
+        self, mock_vitest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
+    ) -> None:
+        """Should use singleton test_framework when parameter is not provided."""
+        mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock(), None, None)
+        (tmp_path / "package.json").write_text('{"name": "test"}')
+
+        # Set singleton to vitest
+        set_current_test_framework("vitest")
+
+        # Don't pass test_framework parameter - should use singleton
+        js_support.run_behavioral_tests(test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path)
+
+        mock_vitest_runner.assert_called_once()
+
+    @patch("codeflash.languages.javascript.test_runner.run_jest_behavioral_tests")
+    def test_explicit_param_overrides_singleton(
+        self, mock_jest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
+    ) -> None:
+        """Explicit test_framework parameter should override singleton."""
+        mock_jest_runner.return_value = (tmp_path / "result.xml", MagicMock(), None, None)
+        (tmp_path / "package.json").write_text('{"name": "test"}')
+
+        # Set singleton to vitest
+        set_current_test_framework("vitest")
+
+        # Pass explicit test_framework=jest - should override singleton
+        js_support.run_behavioral_tests(
+            test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path, test_framework="jest"
+        )
+
+        mock_jest_runner.assert_called_once()
+
+    @patch("codeflash.languages.javascript.vitest_runner.run_vitest_benchmarking_tests")
+    def test_benchmarking_uses_singleton(
+        self, mock_vitest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
+    ) -> None:
+        """run_benchmarking_tests should use singleton when param not provided."""
+        mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock())
+        (tmp_path / "package.json").write_text('{"name": "test"}')
+
+        set_current_test_framework("vitest")
+
+        js_support.run_benchmarking_tests(test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path)
+
+        mock_vitest_runner.assert_called_once()
+
+    @patch("codeflash.languages.javascript.vitest_runner.run_vitest_line_profile_tests")
+    def test_line_profile_uses_singleton(
+        self, mock_vitest_runner: MagicMock, js_support: JavaScriptSupport, mock_test_paths: MagicMock, tmp_path: Path
+    ) -> None:
+        """run_line_profile_tests should use singleton when param not provided."""
+        mock_vitest_runner.return_value = (tmp_path / "result.xml", MagicMock())
+        (tmp_path / "package.json").write_text('{"name": "test"}')
+
+        set_current_test_framework("vitest")
+
+        js_support.run_line_profile_tests(test_paths=mock_test_paths, test_env={}, cwd=tmp_path, project_root=tmp_path)
+
+        mock_vitest_runner.assert_called_once()
+
+
+class TestTestFrameworkSingletonModule:
+    """Tests for the test_framework singleton module itself."""
+
+    def test_initial_state_is_none(self) -> None:
+        """Singleton should start as None."""
+        from codeflash.languages.test_framework import current_test_framework
+
+        assert current_test_framework() is None
+
+    def test_set_and_get(self) -> None:
+        """Should be able to set and get test framework."""
+        from codeflash.languages.test_framework import current_test_framework, set_current_test_framework
+
+        set_current_test_framework("vitest")
+        assert current_test_framework() == "vitest"
+
+    def test_set_only_once(self) -> None:
+        """Once set, singleton should not change."""
+        from codeflash.languages.test_framework import current_test_framework, set_current_test_framework
+
+        set_current_test_framework("jest")
+        set_current_test_framework("vitest")  # Should be ignored
+        assert current_test_framework() == "jest"
+
+    def test_is_jest(self) -> None:
+        """is_jest() should return True when framework is Jest."""
+        from codeflash.languages.test_framework import is_jest, set_current_test_framework
+
+        set_current_test_framework("jest")
+        assert is_jest() is True
+
+    def test_is_vitest(self) -> None:
+        """is_vitest() should return True when framework is Vitest."""
+        from codeflash.languages.test_framework import is_vitest, set_current_test_framework
+
+        set_current_test_framework("vitest")
+        assert is_vitest() is True
+
+    def test_get_js_test_framework_or_default_returns_jest(self) -> None:
+        """get_js_test_framework_or_default should return 'jest' when not set."""
+        from codeflash.languages.test_framework import get_js_test_framework_or_default
+
+        assert get_js_test_framework_or_default() == "jest"
+
+    def test_get_js_test_framework_or_default_returns_vitest(self) -> None:
+        """get_js_test_framework_or_default should return 'vitest' when set."""
+        from codeflash.languages.test_framework import get_js_test_framework_or_default, set_current_test_framework
+
+        set_current_test_framework("vitest")
+        assert get_js_test_framework_or_default() == "vitest"