case studies
Selectivity Finds the Two CSV Records Behind a Calculation Bug
A CSV importer can be wrong for a reason that disappears when a developer tests one record at a time. The example here needs a sequence: a discount for an order, followed …
Selectivity v0.1.1 - Apache 2.0
Make the failing input small enough to understand
Give Selectivity a file or directory and a command that recognizes the failure. It removes material, checks what remains and saves the reductions that preserve the behavior you care about.
20000 to 2
Lines in the saved demonstration
Fresh copies
Each observation starts from snapshot bytes
JSONL
A record of every candidate check
Apache 2.0
Open source Go code
The line count is from a generated fixture with two known trigger lines. It illustrates reduction, without measuring performance on real bugs.
Guides and notes
case studies
Selectivity Isolates Numeric Precision Loss in JSON Lines
An input can be perfectly valid and still expose a disagreement between two consumers. In this example, one path keeps an integer identifier exactly as parsed. The other …
case studies
Selectivity Keeps a Useful Checkpoint When the Test Budget Runs Out
A reduction can be useful before it is finished. That matters when the predicate is expensive, a CI job has a fixed allowance, or a developer wants to make a first pass …
input reduction
Selectivity Makes Large Bug Reports Easier to Understand
A minimal reproducer is a small example that still demonstrates a problem. It gives the person investigating a bug less material to read and fewer irrelevant details to …
case studies
Selectivity Reduces a Configuration Bundle by Files and Lines
The directory demonstration asks a slightly different question from the single-file example: can the reducer find both the relevant files and the relevant lines within …
case studies
Selectivity Reduces a Generated File From 20000 Lines to Two
The line-reduction demonstration starts with a deliberately oversized text file whose answer is known in advance. It has 20000 lines: alpha appears on line 702, omega on …
release
Selectivity Reduces Failing Inputs and Records Every Candidate Check
A useful bug report often begins with an unhelpfully large attachment. The program fails on a particular export, configuration bundle or text file, but nobody knows which …
project name
Selectivity Takes Its Name From the Rule That Chooses What Survives
Selectivity is named for the decision at the center of every reduction. Some parts of an input are necessary to preserve the behavior under investigation. Other parts can …
testing
Selectivity Tests Input Preservation and Uncertain Predicates
The central promise of a reducer is easy to state and surprisingly easy to weaken: the saved input should be smaller, while still satisfying the behavior being …
Bring a better bug report
Start with the quick start, inspect the predicate contract, or read the code and recorded checks.