Glossary

Choice. A single primitive decision made while generating a test case: an integer, float, boolean, byte string, or string, drawn under constraints such as a range.

Choice sequence. The choices a test case made, in order. Strategies build values from it, so replaying the sequence rebuilds the values. The example database, reproduce blobs, and the shrinker all work on choice sequences.

Command. In model-based testing, a struct representing one operation: it generates itself from the model, updates the model, and runs on the system under test.

Constraint type. A wrapper type such as Positive[T] or NonEmpty[T] that puts a constraint on generated values in the type.

Coverage requirement. A declaration, with cover, that some share of test cases should satisfy a condition.

Distinct failure. A failure with its own origin, the location its error was raised. Distinct failures are shrunk and reported separately.

Example database. The directory where proptest saves the choice sequences of failing test cases, to replay them in later runs.

Explain phase. After shrinking, the phase that finds which arguments of the minimal example can vary without changing the failure.

Explicit example. An input given by hand to check_examples, always tested, never shrunk.

Health check. A check that the test can be tested well: that its strategies don’t reject too much, or generate data too large or too slow.

Invalid test case. A test case rejected by assume, a filter, or Outcome.discard(). Invalid test cases don’t count towards max_examples.

Minimal example. The failing input proptest reports: the result of shrinking.

Model. A simple value describing the state a system under test should be in, used to check the system’s behaviour.

Overrun. A test case abandoned because it made too many choices.

Property. A statement that should hold for every input in a domain, written as a test function.

Shrinking. Searching for a simpler failing test case by simplifying the choice sequence of a failing one.

Span. A run of choices that together make one value, recorded by data.draw. The shrinker uses spans to delete, reorder, and simplify values.

State machine. A stateful test, defined as rules or transitions that are run in random sequences against a system.

Strategy. A description of the values a test should be given: a struct conforming to Strategy, which draws a value from a ConjectureData.

SUT. System under test.

Swarm testing. Disabling a random subset of a state machine’s rules in each test case, to make lopsided programs more likely.

Targeting. Steering the search towards inputs with high scores, reported with data.target.

Test case. One run of the test function on one generated input.