▼Expect:   First Class Assertions
►4 Boolean and Logic Expectations
On this page:
expect-true
expect-false
expect-not-false
expect-pred
expect-all
expect-and
expect-conjoin
expect-disjoin
4.1 Boolean Attributes
not-attribute
make-not-attribute
pred-attribute
make-pred-attribute
and-attribute
make-and-attribute
or-attribute
make-or-attribute
7.7
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4 Boolean and Logic Expectations

value

expect-true : expectation?

value

expect-false : expectation?

value

expect-not-false : expectation?

Expectations that expect a value is either #t , #f, or not #f respectively. Returned faults have self-attribute values in the expected field, except for expect-not-false which wraps a self-attribute value in a not-attribute value.

Examples:
> (expect! 'foo expect-true)

expected true

  subject: 'foo

  expected: #t

  actual: 'foo

> (expect! 'foo expect-false)

expected false

  subject: 'foo

  expected: #f

  actual: 'foo

> (expect! 'foo expect-not-false)
> (expect! #f expect-not-false)

expected not false

  subject: #f

  expected: not #f

  actual: #f

procedure

(expect-pred pred) → expectation?

  pred : predicate/c
Returns an expectation that expects a value results in (pred v) returning #t. Returned faults have pred-attribute values and self-attribute values in their expected and actual fields respectively.

Examples:
> (expect! 10 (expect-pred number?))
> (expect! 'foo (expect-pred number?))

expected a different kind of value

  subject: 'foo

  expected: number?

  actual: 'foo

procedure

(expect-all exp ...) → expectation?

  exp : expectation?
Returns an expectation that expects everything that each of the given exp values expects. All expectations are tested and each expectation’s faults are returned together with all other faults. To combine expectations in a way where later expectations are tested only if earlier ones pass, see expect-and.

Examples:
> (define positive-even
    (expect-all (expect-pred positive?) (expect-pred even?)))
> (expect! 4 positive-even)
> (expect! 7 positive-even)

expected a different kind of value

  subject: 7

  expected: even?

  actual: 7

> (expect! -4 positive-even)

expected a different kind of value

  subject: -4

  expected: positive?

  actual: -4

> (expect! -7 positive-even)

multiple failures

  subject: -7

  fault: expected a different kind of value

   expected: positive?

   actual: -7

  fault: expected a different kind of value

   expected: even?

   actual: -7

procedure

(expect-and exp ...) → expectation?

  exp : expectation?
Returns an expectation that expects everything that each of the given exp values expects. Each expectation is tested in order and if any expectation finds any faults, those faults are returned immediately and the remaining exp expectations are not tested. To combine expectations in a way where all expectations are tested and all faults returned together, see expect-all.

Examples:
> (define (small? x) (< x 10))
> (define small-number
    (expect-and (expect-pred real?)
                (expect-pred positive?)
                (expect-pred small?)))
> (expect! 5 small-number)
> (expect! 20 small-number)

expected a different kind of value

  subject: 20

  expected: small?

  actual: 20

> (expect! -4 small-number)

expected a different kind of value

  subject: -4

  expected: positive?

  actual: -4

> (expect! 'foo small-number)

expected a different kind of value

  subject: 'foo

  expected: real?

  actual: 'foo

procedure

(expect-conjoin pred ...) → expectation?

  pred : predicate/c
Equivalent to (expect-and (expect-pred pred) ...).

procedure

(expect-disjoin pred ...) → expectation?

  pred : predicate/c
Returns an expectation that expects a value that satisfies at least one of the given pred functions. If no pred returns #t for the checked value, a single fault is found with an or-attribute value containing a list of pred-attribute values in or-attribute-cases.

Examples:
> (define exp-str-or-sym (expect-disjoin string? symbol?))
> (expect! "foo" exp-str-or-sym)
> (expect! 'foo exp-str-or-sym)
> (expect! 42 exp-str-or-sym)

expected a different kind of value

  subject: 42

  expected: string? or symbol?

  actual: 42

4.1 Boolean Attributes

struct

(struct not-attribute attribute (negated)
    #:transparent)
  negated : attribute?

procedure

(make-not-attribute negated) → not-attribute?

  negated : attribute?
An attribute and its constructor that negates the meaning of negated. The description of a constucted attribute has the format "not  (attribute-description negated) ".

struct

(struct pred-attribute attribute (value)
    #:transparent)
  value : predicate/c

procedure

(make-pred-attribute value) → pred-attribute?

  value : predicate/c
An attribute and its constructor that represents whether or not the input value satisfies the value predicate.

struct

(struct and-attribute attribute (cases)
    #:transparent)
  cases : (listof attribute?)

procedure

(make-and-attribute cases    
  [#:description desc]) → and-attribute?
  cases : (listof attribute?)
  desc : (or/c string? #f) = #f
An attribute and its constructor that describes that a fault refers to every one of cases. This is useful for collapsing multiple nearly identical faults into a single fault; see expect-contains-all? for an example. If desc is not provided, it defaults to the descriptions of each of cases joined with commas and an and between the last two descriptions.

struct

(struct or-attribute attribute (cases)
    #:transparent)
  cases : (listof attribute?)

procedure

(make-or-attribute cases    
  [#:description desc]) → or-attribute?
  cases : (listof attribute?)
  desc : (or/c string? #f) = #f
An attribute and its constructor that describes at least one of cases. A fault might use this to describe that it expected one of multiple possible values. If desc is not provided, it defaults to the descriptions of each of cases joined with commas and an or between the last two descriptions.

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