Understand the failure.
Verify the repair.
Small, reproducible software failures. The broken implementation, the fix that didn’t work, and the one that passed—preserved together.
Explore the cases ↓How results are verified ↗WHAT THE ARCHIVE CONTAINS
100840 executable cases. 20168 are open.
Every case records the implementation that fails, the fix that did not work, and the repair that passed its checks—with recorded outputs and source hashes. This release adds 100840 cases across 20168 failure mechanisms and 254 domains.
The open tier gives you the failure and the unsuccessful fix for one case in every mechanism. The remaining 80672 cases, 5 variants per mechanism, are member-only: the verified repair, its recorded checks, and the full fixture suite are held in the member archive. Read the methodology ↗
A RECORD OF WHAT WENT WRONG
Browse the archive / 100840
Effective basis points are truncated · case 01
An effective rate of 8.4296% is reported as 842 bps instead of 843 bps.
Effective basis points are truncated · case 02
An effective rate of 8.4296% is reported as 842 bps instead of 843 bps.
Effective basis points are truncated · case 03
An effective rate of 8.4296% is reported as 842 bps instead of 843 bps.
Effective basis points are truncated · case 04
An effective rate of 8.4296% is reported as 842 bps instead of 843 bps.
Effective basis points are truncated · case 05
An effective rate of 8.4296% is reported as 842 bps instead of 843 bps.
The first bracket rate is reported while deduction headroom remains · case 01
A filer earning below the deduction is told the next dollar is taxed at 10%.
The first bracket rate is reported while deduction headroom remains · case 02
A filer earning below the deduction is told the next dollar is taxed at 10%.
The first bracket rate is reported while deduction headroom remains · case 03
A filer earning below the deduction is told the next dollar is taxed at 10%.
The first bracket rate is reported while deduction headroom remains · case 04
A filer earning below the deduction is told the next dollar is taxed at 10%.
The first bracket rate is reported while deduction headroom remains · case 05
A filer earning below the deduction is told the next dollar is taxed at 10%.
The tax table uses the bottom of each band instead of its midpoint · case 01
Tax-table amounts are systematically a few dollars low.
The tax table uses the bottom of each band instead of its midpoint · case 02
Tax-table amounts are systematically a few dollars low.
The tax table uses the bottom of each band instead of its midpoint · case 03
Tax-table amounts are systematically a few dollars low.
The tax table uses the bottom of each band instead of its midpoint · case 04
Tax-table amounts are systematically a few dollars low.
The tax table uses the bottom of each band instead of its midpoint · case 05
Tax-table amounts are systematically a few dollars low.
Every table band is 50 dollars wide · case 01
Low incomes are looked up in 50-dollar bands.
Every table band is 50 dollars wide · case 02
Low incomes are looked up in 50-dollar bands.
Every table band is 50 dollars wide · case 03
Low incomes are looked up in 50-dollar bands.
Every table band is 50 dollars wide · case 04
Low incomes are looked up in 50-dollar bands.
Every table band is 50 dollars wide · case 05
Low incomes are looked up in 50-dollar bands.
Tax-table amounts keep cents · case 01
Table lookups report cents although the table is in whole dollars.
Tax-table amounts keep cents · case 02
Table lookups report cents although the table is in whole dollars.
Tax-table amounts keep cents · case 03
Table lookups report cents although the table is in whole dollars.
Tax-table amounts keep cents · case 04
Table lookups report cents although the table is in whole dollars.
Tax-table amounts keep cents · case 05
Table lookups report cents although the table is in whole dollars.
Incomes under five dollars are charged a table amount · case 01
A filer with 3 dollars of taxable income owes 1 dollar.
Incomes under five dollars are charged a table amount · case 02
A filer with 3 dollars of taxable income owes 1 dollar.
Incomes under five dollars are charged a table amount · case 03
A filer with 3 dollars of taxable income owes 1 dollar.
Incomes under five dollars are charged a table amount · case 04
A filer with 3 dollars of taxable income owes 1 dollar.
Incomes under five dollars are charged a table amount · case 05
A filer with 3 dollars of taxable income owes 1 dollar.
The exemption phase-out is computed on total AMTI instead of the excess · case 01
The exemption disappears for filers barely over the threshold.
The exemption phase-out is computed on total AMTI instead of the excess · case 02
The exemption disappears for filers barely over the threshold.
The exemption phase-out is computed on total AMTI instead of the excess · case 03
The exemption disappears for filers barely over the threshold.
The exemption phase-out is computed on total AMTI instead of the excess · case 04
The exemption disappears for filers barely over the threshold.
The exemption phase-out is computed on total AMTI instead of the excess · case 05
The exemption disappears for filers barely over the threshold.
A fully phased-out exemption turns negative and inflates the AMT base · case 01
Very high AMTI yields a base larger than AMTI itself.
A fully phased-out exemption turns negative and inflates the AMT base · case 02
Very high AMTI yields a base larger than AMTI itself.
A fully phased-out exemption turns negative and inflates the AMT base · case 03
Very high AMTI yields a base larger than AMTI itself.
A fully phased-out exemption turns negative and inflates the AMT base · case 04
Very high AMTI yields a base larger than AMTI itself.
A fully phased-out exemption turns negative and inflates the AMT base · case 05
Very high AMTI yields a base larger than AMTI itself.
The 28% AMT rate is applied to the whole base once it crosses the break · case 01
Crossing the 232600 break raises the tax on the entire base by two points.
The 28% AMT rate is applied to the whole base once it crosses the break · case 02
Crossing the 232600 break raises the tax on the entire base by two points.
The 28% AMT rate is applied to the whole base once it crosses the break · case 03
Crossing the 232600 break raises the tax on the entire base by two points.
The 28% AMT rate is applied to the whole base once it crosses the break · case 04
Crossing the 232600 break raises the tax on the entire base by two points.
The 28% AMT rate is applied to the whole base once it crosses the break · case 05
Crossing the 232600 break raises the tax on the entire base by two points.
AMT is reported as negative when regular tax exceeds the tentative minimum tax · case 01
Filers with high regular tax receive a negative AMT that reduces their total.
AMT is reported as negative when regular tax exceeds the tentative minimum tax · case 02
Filers with high regular tax receive a negative AMT that reduces their total.
AMT is reported as negative when regular tax exceeds the tentative minimum tax · case 03
Filers with high regular tax receive a negative AMT that reduces their total.
AMT is reported as negative when regular tax exceeds the tentative minimum tax · case 04
Filers with high regular tax receive a negative AMT that reduces their total.
AMT is reported as negative when regular tax exceeds the tentative minimum tax · case 05
Filers with high regular tax receive a negative AMT that reduces their total.
The exemption reduction is rounded to the nearest dollar · case 01
The exemption is a dollar lower than stipulated for some excess amounts.
The exemption reduction is rounded to the nearest dollar · case 02
The exemption is a dollar lower than stipulated for some excess amounts.
The exemption reduction is rounded to the nearest dollar · case 03
The exemption is a dollar lower than stipulated for some excess amounts.
The exemption reduction is rounded to the nearest dollar · case 04
The exemption is a dollar lower than stipulated for some excess amounts.
The exemption reduction is rounded to the nearest dollar · case 05
The exemption is a dollar lower than stipulated for some excess amounts.
Joint filers receive the single AMT exemption · case 01
Married couples pay AMT computed with the single exemption.
Joint filers receive the single AMT exemption · case 02
Married couples pay AMT computed with the single exemption.
Joint filers receive the single AMT exemption · case 03
Married couples pay AMT computed with the single exemption.
Joint filers receive the single AMT exemption · case 04
Married couples pay AMT computed with the single exemption.
Joint filers receive the single AMT exemption · case 05
Married couples pay AMT computed with the single exemption.
The surtax is levied on the greater of NII and the MAGI excess · case 01
A filer with small investment income pays surtax on their wages above the threshold.
The surtax is levied on the greater of NII and the MAGI excess · case 02
A filer with small investment income pays surtax on their wages above the threshold.
The surtax is levied on the greater of NII and the MAGI excess · case 03
A filer with small investment income pays surtax on their wages above the threshold.
The surtax is levied on the greater of NII and the MAGI excess · case 04
A filer with small investment income pays surtax on their wages above the threshold.
The surtax is levied on the greater of NII and the MAGI excess · case 05
A filer with small investment income pays surtax on their wages above the threshold.
Separate filers use the joint threshold · case 01
Married-filing-separately returns escape the surtax up to 250000.
Separate filers use the joint threshold · case 02
Married-filing-separately returns escape the surtax up to 250000.
Separate filers use the joint threshold · case 03
Married-filing-separately returns escape the surtax up to 250000.
Separate filers use the joint threshold · case 04
Married-filing-separately returns escape the surtax up to 250000.
Separate filers use the joint threshold · case 05
Married-filing-separately returns escape the surtax up to 250000.
An investment loss produces a negative surtax · case 01
A net investment loss reduces other tax through a negative surtax.
An investment loss produces a negative surtax · case 02
A net investment loss reduces other tax through a negative surtax.
An investment loss produces a negative surtax · case 03
A net investment loss reduces other tax through a negative surtax.
An investment loss produces a negative surtax · case 04
A net investment loss reduces other tax through a negative surtax.
An investment loss produces a negative surtax · case 05
A net investment loss reduces other tax through a negative surtax.
Marginal relief is measured from the lower limit instead of the upper limit · case 01
Relief grows as profits rise, so companies near the upper limit pay less than at the lower limit.
Marginal relief is measured from the lower limit instead of the upper limit · case 02
Relief grows as profits rise, so companies near the upper limit pay less than at the lower limit.
Marginal relief is measured from the lower limit instead of the upper limit · case 03
Relief grows as profits rise, so companies near the upper limit pay less than at the lower limit.
Marginal relief is measured from the lower limit instead of the upper limit · case 04
Relief grows as profits rise, so companies near the upper limit pay less than at the lower limit.
Marginal relief is measured from the lower limit instead of the upper limit · case 05
Relief grows as profits rise, so companies near the upper limit pay less than at the lower limit.
Associated companies do not share the limits · case 01
Each company in a group gets the full small-profits limit.
Associated companies do not share the limits · case 02
Each company in a group gets the full small-profits limit.
Associated companies do not share the limits · case 03
Each company in a group gets the full small-profits limit.
Associated companies do not share the limits · case 04
Each company in a group gets the full small-profits limit.
Associated companies do not share the limits · case 05
Each company in a group gets the full small-profits limit.
Short accounting periods receive full-year limits · case 01
A six-month period enjoys the full annual small-profits limit.
Short accounting periods receive full-year limits · case 02
A six-month period enjoys the full annual small-profits limit.
Short accounting periods receive full-year limits · case 03
A six-month period enjoys the full annual small-profits limit.
Short accounting periods receive full-year limits · case 04
A six-month period enjoys the full annual small-profits limit.
Short accounting periods receive full-year limits · case 05
A six-month period enjoys the full annual small-profits limit.
Exempt dividends are ignored when choosing the rate band · case 01
A company whose dividends lift it above the limit keeps small-profits treatment.
Exempt dividends are ignored when choosing the rate band · case 02
A company whose dividends lift it above the limit keeps small-profits treatment.
Exempt dividends are ignored when choosing the rate band · case 03
A company whose dividends lift it above the limit keeps small-profits treatment.
Exempt dividends are ignored when choosing the rate band · case 04
A company whose dividends lift it above the limit keeps small-profits treatment.
Exempt dividends are ignored when choosing the rate band · case 05
A company whose dividends lift it above the limit keeps small-profits treatment.
First-time-buyer relief is applied above the price cap · case 01
A 700000 purchase by a first-time buyer is taxed only on the 425000-625000 slice.
First-time-buyer relief is applied above the price cap · case 02
A 700000 purchase by a first-time buyer is taxed only on the 425000-625000 slice.
First-time-buyer relief is applied above the price cap · case 03
A 700000 purchase by a first-time buyer is taxed only on the 425000-625000 slice.
First-time-buyer relief is applied above the price cap · case 04
A 700000 purchase by a first-time buyer is taxed only on the 425000-625000 slice.
First-time-buyer relief is applied above the price cap · case 05
A 700000 purchase by a first-time buyer is taxed only on the 425000-625000 slice.
INSPECTABLE BY DESIGN
Every result has a runnable source.
Runnable implementations with recorded outputs, source hashes, and explicit contracts. Related variants share a failure mechanism and belong together in evaluation splits.
Read the methodology ↗