Evidence, not a badge
Accuracy & testing center
Reproducible scenarios, published expected outputs, rule provenance, and the limits of what automated testing can prove.
What “tested” means on PayCalc
PayCalc uses three layers of checks. Unit tests exercise calculation functions directly. Integration tests compare jurisdiction behavior and rule normalization. A Playwright browser suite opens the actual website, changes form controls, and asserts the values users see. The live workflow is configured to run after Hostinger deployments and daily against https://paycalc.org/.
Tests are evidence of implementation consistency, not certification by the IRS, a state agency, lender, accountant, or investment professional. When an official rule changes, the rule and expected test result must be reviewed together.
Representative production regression matrix
The cases below are intentionally concrete so a visitor can reproduce a scenario in the public calculator rather than rely on a generic “accurate” claim.
| Tool | Scenario | Inputs / setup | Expected displayed result |
|---|---|---|---|
| Paycheck | TX single, $65k, biweekly | Gross $2,500.00 | Federal $216.15; SS $155.00; Medicare $36.25; net $2,092.60 |
| Paycheck | W-4 Step 3 credits = $2,200 | Same baseline | Federal $131.54 |
| Paycheck | Traditional 401(k) = $100 | Same baseline | Federal $204.15; SS $155.00; Medicare $36.25 |
| Paycheck | Section 125 health = $100 | Same baseline | Federal $204.15; SS $148.80; Medicare $34.80 |
| Paycheck | YTD Social Security wages = $183,000 | Same baseline | Social Security $93.00 |
| Paycheck | YTD Medicare wages = $199,000 | Same baseline | Medicare $49.75 incl. $13.50 additional |
| Paycheck | $1,000 separately identified bonus | Flat supplemental method | Federal $436.15 total |
| Paycheck | California $65k biweekly | Single | CA PIT $90.01; SDI $32.50 |
| Paycheck | Washington $65k biweekly | Single | State income tax $0.00; payroll programs $34.68 |
| Paycheck | New York $120k semimonthly | Single; 1 allowance | State $258.51 |
| Paycheck | Pennsylvania $65k biweekly | $100 traditional retirement | PIT $76.75; employee UC $1.75 |
| Paycheck | Indiana $41,600 weekly | Published exemption/local inputs | State $13.96; local $4.73 |
| Paycheck | Maryland $120k annual | Garrett County | Combined modeled state/local $8,669.90 |
| Paycheck | Wisconsin $18,200 weekly | Single; 1 allowance | State $7.59 |
| Paycheck | Arizona $52k weekly | 2.0% A-4 election | State $20.00 |
| Mortgage | Default fixed-rate scenario | $360k loan; 6.5%; 30 years | P&I $2,275.44; interest $459,160.16 |
| Mortgage | 15-year direct loan | $400k; 5%; 15 years | P&I $3,163.17; interest $169,371.41 |
| Mortgage | Zero-interest boundary | $120k; 0%; 30 years | P&I $333.33; interest $0.00 |
| Mortgage | Extra-principal scenario | $300k; 6%; +$250/month | Payoff 22y 1m; saves 7y 11m |
| Mortgage | PMI scenario | Default + $150/month PMI | Monthly total $3,025.44 |
| Investment | Baseline compound growth | $10k; 7% annual; 3 years | Final $12,250.43; gain $2,250.43 |
| Investment | Monthly periods | $10k; 1% monthly; 12 months | Final $11,268.25 |
| Investment | Negative return | $10k; -10% annual; 3 years | Final $7,290.00; loss $2,710.00 |
| Investment | Incomplete annual period | $10k; 11-month duration | 0 completed annual periods; final $10,000.00 |
| Investment | Rental yield | $1M value; $80k rent; $10k expenses | Net income $70k; net yield 7%; gross 8% |
How failures are handled
A failed regression blocks the corresponding validation workflow until the discrepancy is investigated. A failure can mean implementation changed, the expectation is stale, the interface broke, or a production resource failed to deploy. The expected value is not simply changed to make a red test green; the source rule or model must support the behavior.
Rule provenance matters too
A calculator can consistently reproduce the wrong rule. PayCalc therefore pairs tests with source provenance. Every payroll jurisdiction links to its primary official source in the 2026 Payroll Tax Source Directory. The Methodology explains the model boundaries for all three tools.
Maintenance cadence
Federal, California, Indiana, and Washington monitor workflows check selected official sources, while the live browser suite is scheduled daily. Not every government publication exposes a stable machine-readable endpoint, so PayCalc does not claim automatic daily revalidation of all 52 jurisdiction records.
The Update History records material changes. We do not change “last updated” dates merely to make pages appear fresh.