Trait extended by matcher objects, which may appear after the word have, that can match against a
property of the type specified by the HavePropertyMatcher's second type parameter P.
HavePropertyMatcher's first type parameter, T, specifies the type that declares the property. The match will succeed if and
only if the value of the property equals the specified value.
The object containing the property
is passed to the HavePropertyMatcher's
apply method. The result is a HavePropertyMatchResult[P].
A HavePropertyMatcher is, therefore, a function from the specified type, T, to
a HavePropertyMatchResult[P].
Although HavePropertyMatcher
and Matcher represent similar concepts, they have no inheritance relationship
because Matcher is intended for use right after should or must
whereas HavePropertyMatcher is intended for use right after have.
A HavePropertyMatcher essentially allows you to write statically typed
property assertions similar to the dynamic ones that use symbols:
book should have ('title ("Moby Dick")) // dynamic: uses reflection
book should have (title ("Moby Dick")) // type safe: only works on Books; no reflection used
One good way to organize custom matchers is to place them inside one or more traits that
you can then mix into the suites or specs that need them. Here's an example that
includes two methods that produce HavePropertyMatchers:
case class Book(val title: String, val author: String)trait CustomMatchers {
def title(expectedValue: String) = new HavePropertyMatcher[Book, String] { def apply(book: Book) = HavePropertyMatchResult( book.title == expectedValue, "title", expectedValue, book.title ) }
def author(expectedValue: String) = new HavePropertyMatcher[Book, String] { def apply(book: Book) = HavePropertyMatchResult( book.author == expectedValue, "author", expectedValue, book.author ) } }
Each time the title method is called, it returns a new HavePropertyMatcher[Book, String] that
can be used to match against the title property of the Book passed to its apply
method. Because the type parameter of these two HavePropertyMatchers is Book, they
can only be used with instances of that type. (The compiler will enforce this.) The match will succeed if the
title property equals the value passed as expectedValue.
If the match succeeds, the matches field of the returned HavePropertyMatchResult will be true.
The second field, propertyName, is simply the string name of the property.
The third and fourth fields, expectedValue and actualValue indicate the expected and actual
values, respectively, for the property.
Here's an example that uses these HavePropertyMatchers:
class ExampleSpec extends Spec with ShouldMatchers with CustomMatchers { describe("A book") {
it("should have the correct title and author") {
val book = Book("Moby Dick", "Melville")
book should have (
title ("Moby Dick"),
author ("Melville")
)
}
}
}
These matches should succeed, but if for example the first property, title ("Moby Dick"), were to fail, you would get an error message like:
The title property had value "A Tale of Two Cities", instead of its expected value "Moby Dick", on object Book(A Tale of Two Cities,Dickens)
For more information on HavePropertyMatchResult and the meaning of its fields, please
see the documentation for HavePropertyMatchResult. To understand why HavePropertyMatcher
is contravariant in its type parameter, see the section entitled "Matcher's variance" in the
documentation for Matcher.
Check to see if a property on the specified object, objectWithProperty, matches its
expected value, and report the result in
the returned HavePropertyMatchResult. The objectWithProperty is
usually the value to the left of a should or must invocation. For example, book
would be passed as the objectWithProperty in:
Check to see if a property on the specified object, objectWithProperty, matches its
expected value, and report the result in
the returned HavePropertyMatchResult. The objectWithProperty is
usually the value to the left of a should or must invocation. For example, book
would be passed as the objectWithProperty in:
book should have (title ("Moby Dick"))
the object with the property against which to match
the HavePropertyMatchResult that represents the result of the match
Compose this HavePropertyMatcher with the passed function, returning a new HavePropertyMatcher.
Compose this HavePropertyMatcher with the passed function, returning a new HavePropertyMatcher.
This method overrides compose on Function1 to
return a more specific function type of HavePropertyMatcher.
Returns a string representation of the object.
Returns a string representation of the object.
The default representation is platform dependent.
a string representation of the object.
Trait extended by matcher objects, which may appear after the word
have, that can match against a property of the type specified by theHavePropertyMatcher's second type parameterP.HavePropertyMatcher's first type parameter,T, specifies the type that declares the property. The match will succeed if and only if the value of the property equals the specified value. The object containing the property is passed to theHavePropertyMatcher'sapplymethod. The result is aHavePropertyMatchResult[P]. AHavePropertyMatcheris, therefore, a function from the specified type,T, to aHavePropertyMatchResult[P].Although
HavePropertyMatcherandMatcherrepresent similar concepts, they have no inheritance relationship becauseMatcheris intended for use right aftershouldormustwhereasHavePropertyMatcheris intended for use right afterhave.A
HavePropertyMatcheressentially allows you to write statically typed property assertions similar to the dynamic ones that use symbols:book should have ('title ("Moby Dick")) // dynamic: uses reflection book should have (title ("Moby Dick")) // type safe: only works on Books; no reflection usedOne good way to organize custom matchers is to place them inside one or more traits that you can then mix into the suites or specs that need them. Here's an example that includes two methods that produce
HavePropertyMatchers:Each time the
titlemethod is called, it returns a newHavePropertyMatcher[Book, String]that can be used to match against thetitleproperty of theBookpassed to itsapplymethod. Because the type parameter of these twoHavePropertyMatchers isBook, they can only be used with instances of that type. (The compiler will enforce this.) The match will succeed if thetitleproperty equals the value passed asexpectedValue. If the match succeeds, thematchesfield of the returnedHavePropertyMatchResultwill betrue. The second field,propertyName, is simply the string name of the property. The third and fourth fields,expectedValueandactualValueindicate the expected and actual values, respectively, for the property. Here's an example that uses theseHavePropertyMatchers:class ExampleSpec extends Spec with ShouldMatchers with CustomMatchers {describe("A book") {
it("should have the correct title and author") {
val book = Book("Moby Dick", "Melville")
book should have ( title ("Moby Dick"), author ("Melville") ) } } }
These matches should succeed, but if for example the first property,
title ("Moby Dick"), were to fail, you would get an error message like:For more information on
HavePropertyMatchResultand the meaning of its fields, please see the documentation forHavePropertyMatchResult. To understand whyHavePropertyMatcheris contravariant in its type parameter, see the section entitled "Matcher's variance" in the documentation forMatcher.