▼Expect:   First Class Assertions
►6 Text and String Expectations
On this page:
expect-regexp-match
expect-string-contains?
expect-output
6.1 String Attributes and Contexts
regexp-match-context
make-regexp-match-context
regexp-match-attribute
make-regexp-match-attribute
the-output-context
8.12
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6 Text and String Expectations🔗ℹ

procedure

(expect-regexp-match pattern [result-exp]) → expectation?

  pattern : regexp?
  result-exp : 
(or/c (listof (or/c string? bytes? #f expectation?))
      expectation?)
   = expect-not-false
Returns an expectation that expects a value is either a string, a bytestring, a path, or a port. Then, the value is matched against pattern using regexp-match and the match result is checked with result-exp. Using the default for result-exp checks that pattern matches the input value and ignores the result of the match. If result-exp is not an expectation, it is converted to one with ->expectation.

Examples:
> (expect! "This is some message" (expect-regexp-match #rx"some"))
> (expect! "12x4x6" (expect-regexp-match #rx"x." '("x4")))
> (expect! "12x4x6" (expect-regexp-match #rx"x." '("x6")))

expected a different value

  subject: "12x4x6"

  in: the results of matching #rx"x."

  in: item at position 0

  expected: equal? to "x6"

  actual: "x4"

procedure

(expect-string-contains? str) → expectation?

  str : string?
Returns an expectation that expects a string that contains str. Convenient shorthand for combining expect-contains with expect-pred and string?.

Examples:
> (expect! "This is some message" (expect-string-contains? "some message"))
> (expect! "This is some message" (expect-string-contains? "foo"))

expected a value to be contained

  subject: "This is some message"

  expected: "foo" contained with string-contains?

  actual: "This is some message"

procedure

(expect-output exp [#:call call-exp]) → expectation?

  exp : (or/c string? regexp? expectation?)
  call-exp : expectation? = expect-not-raise
Returns an expectation that expects a thunk. That thunk is called and the string it writes to current-output-port is checked against exp. If exp is not an expectation, it is converted to one with either expect-regexp-match if it’s a regexp or ->expectation otherwise.

Examples:
> (define (foo) (display "foo!!!"))
> (expect! foo (expect-output "foo!!!"))
> (expect! foo (expect-output #rx"foo"))
> (expect! foo (expect-output "bar"))

expected a different value

  subject: #<procedure:foo>

  in: the string written to the output port

  expected: equal? to "bar"

  actual: "foo!!!"

If call-exp is provided, the input thunk is additionally checked against call-exp. This allows asserting both the output of a thunk and other properties of the thunk without calling it twice, for the rare times when multiple calls should be avoided.

Examples:
> (define (foo) (display "foo!!!"))
> (expect! foo (expect-output "foo!!!" #:call (expect-return (void))))
> (expect! foo (expect-output "foo!!!" #:call (expect-raise)))

expected any value raised

  subject: #<procedure:foo>

  in: the raised value

  expected: anything

  actual: nothing

6.1 String Attributes and Contexts🔗ℹ

struct

(struct regexp-match-context context (regexp)
    #:transparent)
  regexp : regexp?

procedure

(make-regexp-match-context regexp) → regexp-match-context?

  regexp : regexp?
A context and its constructor that indicates a fault occurred in the result of calling regexp-match with regexp.

struct

(struct regexp-match-attribute attribute (regexp)
    #:transparent)
  regexp : regexp?

procedure

(make-regexp-match-attribute regexp) → regexp-match-attribute?

  regexp : regexp?
An attribute and its constructor that refers to whether or not a value matches regexp.

value

the-output-context : context?

A context that represents the string written to current-output-port during the evaluation of a thunk.

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