Jest Config Validator

Validate jest.config.ts/js/json and Jest configuration in package.json for deprecated options, transform conflicts, and best practices. Use when validating Jest test runner configs, auditing test setups, migrating Jest versions, or linting jest.config files.

Validate jest.config.ts, jest.config.js, jest.config.json, and package.json#jest for deprecated options, transform conflicts, coverage misconfigurations, and best practices. Supports text, JSON, and summary output formats with CI-friendly exit codes.

Commands

bash

# Full validation (all 22+ rules)
python3 scripts/jest_config_validator.py validate jest.config.js

# Quick syntax-only check (structure rules only)
python3 scripts/jest_config_validator.py check jest.config.ts

# Explain config in human-readable form
python3 scripts/jest_config_validator.py explain jest.config.json

# Suggest improvements
python3 scripts/jest_config_validator.py suggest package.json

# JSON output (CI-friendly)
python3 scripts/jest_config_validator.py validate jest.config.js --format json

# Summary only (pass/fail + counts)
python3 scripts/jest_config_validator.py validate jest.config.js --format summary

# Strict mode (warnings become errors)
python3 scripts/jest_config_validator.py validate jest.config.js --strict

Rules (22+)

#	Category	Severity	Rule
S1	Structure	Error	File not found or unreadable
S2	Structure	Error	Empty config or missing module.exports/export default
S3	Structure	Warning	Both jest.config and package.json#jest present (conflict)
S4	Structure	Warning	Unknown top-level config keys detected
S5	Structure	Error	Invalid JSON syntax (for .json configs)
T1	Test Environment	Error	Invalid testEnvironment value
T2	Test Environment	Warning	testEnvironment: jsdom without jest-environment-jsdom (Jest 28+)
T3	Test Environment	Warning	testURL deprecated in Jest 28+ (use testEnvironmentOptions)
T4	Test Environment	Warning	Empty testMatch or testPathPattern
X1	Transforms	Warning	Overlapping transform patterns (conflict)
X2	Transforms	Warning	ts-jest and babel-jest used together without clear separation
X3	Transforms	Warning	transformIgnorePatterns too broad (may skip needed transforms)
X4	Transforms	Warning	Missing transform for .tsx/.jsx when React detected
V1	Coverage	Warning	collectCoverageFrom empty or too broad
V2	Coverage	Warning	coverageThreshold set but collectCoverage not enabled
V3	Coverage	Warning	Deprecated coverageReporters values
D1	Deprecated	Warning	Deprecated Jest options detected
D2	Deprecated	Warning	jest.fn() used inside config file (configs should not mock)
D3	Deprecated	Warning	timers: 'fake' (old syntax, use fakeTimers object)
B1	Best Practices	Info	No clearMocks/resetMocks/restoreMocks set
B2	Best Practices	Warning	roots pointing outside project directory
B3	Best Practices	Warning	setupFiles/setupFilesAfterFramework path pattern issues
B4	Best Practices	Info	moduleNameMapper with complex regex missing comment
B5	Best Practices	Warning	preset and manual config overlap
B6	Best Practices	Warning	maxWorkers set to 1 in non-CI context

Output Formats

text (default): Human-readable with file path, rule code, severity, and message per finding.

json: Machine-readable JSON with file, summary, and findings array. Each finding has rule, severity, message, and line fields.

summary: One-line pass/fail with error/warning/info counts. Ideal for CI output gates.

Exit Codes

Code	Meaning
0	No errors found (warnings/info may exist)
1	One or more errors found
2	File not found or parse error