test.check cheatsheet

So far this only documents functions in the generators namespace.

Dev utilities, misc

• (gen/sample g) — returns 10 smallish samples from g
• (gen/sample g n) — generates n samples from g
• (gen/generate g) — generates a single moderately sized value from g
• (gen/generate g size) — generates a value from g with the given size (normally sizes range from 0 to 200)
• (gen/generator? g) — checks if g is a generator

Simple Generators

• (gen/return x) — A constant generator that always generates x
• gen/boolean — generates booleans (true and false)
• gen/uuid — generates uniformly random UUIDs, does not shrink
• (gen/elements coll) — generates elements from coll (which must be non-empty)
• (gen/shuffle coll) — generates vectors with the elements of coll in random orders
• gen/any — generates any clojure value
• gen/any-printable — generates any printable clojure value
• gen/simple-type — like gen/any but does not generate collections
• gen/simple-type-printable — like gen/any-printable but does not generate collections

Numbers

• gen/nat — generates small non-negative integers (useful for generating sizes of things)
• gen/large-integer — generates a large range of integers
• variant with options: (gen/large-integer* {:min x, :max y})
• gen/double — generates a large range of doubles (w/ infinities & NaN)
• variant with options: (gen/double* {:min x, :max y, :infinite? true, :NaN? true})
• gen/ratio — generates ratios (sometimes integers)
• gen/byte — generates a Byte

Characters & Strings & Things

• gen/char — generates characters
• gen/char-ascii — generates printable ASCII characters
• gen/char-alphanumeric — generates alphanumeric ASCII characters
• gen/char-alpha — generates alphabetic ASCII characters
• gen/string — generates a string
• gen/string-ascii — generates a string using gen/char-ascii
• gen/string-alphanumeric — generates a string using gen/char-alphanumeric
• gen/keyword — generates keywords
• gen/keyword-ns — generates namespaced keywords
• gen/symbol — generates symbols
• gen/symbol-ns — generates namespaced symbols

Heterogeneous Collections

• (gen/tuple g1 g2 ...) — generates vectors [x1 x2 ...] where x1 is drawn from g1, x2 from g2, etc.
• (gen/hash-map k1 g1, k2 g2, ...) — generates maps {k1 v1, k2 v2, ...} where v1 is drawn from g1, v2 from g2, etc.

Homogeneous Collections

• (gen/vector g) — generates vectors of elements from g
• Variants:
  • (gen/vector g num-elements)
  • (gen/vector g min-elements max-elements)
• (gen/list g) — generates lists of elements from g
• (gen/set g) — generates sets of elements from g
• Variants:
  • (gen/set g {:num-elements x, :max-tries 20})
  • (gen/set g {:min-elements x, :max-elements y, :max-tries 20})
• (gen/map key-gen val-gen) — generates a map with keys from key-gen and vals from val-gen
• same opts as gen/setu
• (gen/sorted-set g) — just like gen/set, but generates sorted-sets
• (gen/vector-distinct g) — same signature as gen/set, but generates vectors of distinct elements
• (gen/list-distinct g) — same signature as gen/set, but generates lists of distinct elements
• (gen/vector-distinct-by key-fn g) — generates vectors of elements where (apply distinct? (map key-fn the-vector))
• same opts as gen/set
• (gen/list-distinct-by key-fn g) — generates list of elements where (apply distinct? (map key-fn the-list))
• same opts as gen/set
• gen/bytes — generates a byte array

Combinators

• (gen/let [x g] y) — macro, like clojure.core/let, where the right-hand bindings are generators and the left-hand are generated values; creates a generator
• same functionality as gen/fmap and gen/bind
• (gen/fmap f g) — creates a generator that generates (f x) for x generated from g
• (gen/bind g f) — similar to gen/fmap, but where (f x) is itself a generator and (gen/bind g f) generates values from (f x)
• (gen/such-that pred g) — returns a new generator that generates only elements from g that match pred
• Variants: (gen/such-that pred g max-tries)
• (gen/one-of [g1 g2 ...]) — generates elements from the given generators, picking generators at random
• (gen/frequency [[2 g1] [7 g2] ...]) — generates elements from the given generators, using the given weights to determine the probability of picking any particular generator
• (gen/not-empty g) — given a generator that generates collections, returns a modified generator that never generates empty collections
• (gen/recursive-gen container-gen scalar-gen) — generates a tree of values, using container-gen (which is a function like gen/list which takes and returns a generator) and scalar-gen (a generator for the leaf values)

Sizing & shrinking control

• (gen/resize n g) — creates a variant of g whose size parameter is always n
• (gen/scale f g) — creates a variant of g whose size parameter is (f size)
• (gen/no-shrink g) — creates a variant of g that does not shrink