Check to see if the specified object, left, matches, and report the result in
the returned MatchResult.
Check to see if the specified object, left, matches, and report the result in
the returned MatchResult. The parameter is named left, because it is
usually the value to the left of a should or must invocation. For example,
in:
num should be (odd)
The be (odd) expression results in a regular Matcher that holds
a reference to odd, the
BeMatcher passed to be. The should method invokes apply
on this matcher, passing in num, which is therefore the "left" value. The
matcher will pass num (the left value) to the BeMatcher's apply
method.
the value against which to match
the MatchResult that represents the result of the match
Compose this BeMatcher with the passed function, returning a new BeMatcher.
Compose this BeMatcher with the passed function, returning a new BeMatcher.
This method overrides compose on Function1 to
return a more specific function type of BeMatcher. For example, given
an odd matcher defined like this:
val odd = new BeMatcher[Int] { def apply(left: Int) = MatchResult( left % 2 == 1, left.toString + " was even", left.toString + " was odd" ) }
You could use odd like this:
3 should be (odd) 4 should not be (odd)
If for some odd reason, you wanted a BeMatcher[String] that
checked whether a string, when converted to an Int,
was odd, you could make one by composing odd with
a function that converts a string to an Int, like this:
val oddAsInt = odd compose { (s: String) => s.toInt }
Now you have a BeMatcher[String] whose apply method first
invokes the converter function to convert the passed string to an Int,
then passes the resulting Int to odd. Thus, you could use
oddAsInt like this:
"3" should be (oddAsInt) "4" should not be (oddAsInt)
Trait extended by matcher objects, which may appear after the word
be, that can match a value of the specified type. The value to match is passed to theBeMatcher'sapplymethod. The result is aMatchResult. ABeMatcheris, therefore, a function from the specified type,T, to aMatchResult.Although
BeMatcherandMatcherrepresent very similar concepts, they have no inheritance relationship becauseMatcheris intended for use right aftershouldormustwhereasBeMatcheris intended for use right afterbe.As an example, you could create
BeMatcher[Int]calledoddthat would match any oddInt, and one calledeventhat would match any evenInt. Given this pair ofBeMatchers, you could check whether anIntwas odd or even with expressions like:Here's is how you might define the odd and even
BeMatchers:These
BeMatchers are defined inside a trait to make them easy to mix into any suite or spec that needs them. TheCustomMatcherscompanion object exists to make it easy to bring theBeMatchers defined in this trait into scope via importing, instead of mixing in the trait. The ability to import them is useful, for example, when you want to use the matchers defined in a trait in the Scala interpreter console.Here's an rather contrived example of how you might use
oddandeven:The last assertion in the above test will fail with this failure message:
6 was evenFor more information on
MatchResultand the meaning of its fields, please see the documentation forMatchResult. To understand whyBeMatcheris contravariant in its type parameter, see the section entitled "Matcher's variance" in the documentation forMatcher.