ScalaTest 1.0
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trait
BePropertyMatcher[-T]
extends
(T) => BePropertyMatchResultbe
, that can match against a Boolean
property. The match will succeed if and only if the Boolean
property equals true
.
The object containing the property, which must be of the type specified by the BePropertyMatcher
's type
parameter T
, is passed to the BePropertyMatcher
's
apply
method. The result is a BePropertyMatchResult
.
A BePropertyMatcher
is, therefore, a function from the specified type, T
, to
a BePropertyMatchResult
.
Although BePropertyMatcher
and Matcher
represent similar concepts, they have no inheritance relationship
because Matcher
is intended for use right after should
or must
whereas BePropertyMatcher
is intended for use right after be
.
A BePropertyMatcher
essentially allows you to write statically typed Boolean
property assertions similar to the dynamic ones that use symbols:
tempFile should be a ('file) // dynamic: uses reflection tempFile should be a (file) // type safe: only works on Files; 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 BePropertyMatcher
s:
trait CustomMatchers { class FileBePropertyMatcher extends BePropertyMatcher[java.io.File] { def apply(left: java.io.File) = BePropertyMatchResult(left.isFile, "file") } class DirectoryBePropertyMatcher extends BePropertyMatcher[java.io.File] { def apply(left: java.io.File) = BePropertyMatchResult(left.isDirectory, "directory") } val file = new FileBePropertyMatcher val directory = new DirectoryBePropertyMatcher }
Because the type parameter of these two BePropertyMatcher
s is java.io.File
, they
can only be used with instances of that type. (The compiler will enforce this.) All they do is create a
BePropertyMatchResult
whose matches
field is true
if and only if the Boolean
property
is true
. The second field, propertyName
, is simply the string name of the property.
The file
and directory
val
s create variables that can be used in
matcher expressions that test whether a java.io.File
is a file or a directory. Here's an example:
class ExampleSpec extends Spec with ShouldMatchers with CustomMatchers { describe("A temp file") { it("should be a file, not a directory") { val tempFile = java.io.File.createTempFile("delete", "me") try { tempFile should be a (file) tempFile should not be a (directory) } finally { tempFile.delete() } } } }
These matches should succeed, but if for example the first match, tempFile should be a (file)
, were to fail, you would get an error message like:
/tmp/delme1234me was not a file
For more information on BePropertyMatchResult
and the meaning of its fields, please
see the documentation for BePropertyMatchResult
. To understand why BePropertyMatcher
is contravariant in its type parameter, see the section entitled "Matcher's variance" in the
documentation for Matcher
.
Method Summary | |
abstract def
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apply
(objectWithProperty : T) : BePropertyMatchResult
Check to see if a
Boolean property on the specified object, objectWithProperty , matches its
expected value, and report the result in
the returned BePropertyMatchResult . The objectWithProperty is
usually the value to the left of a should or must invocation. For example, tempFile
would be passed as the objectWithProperty in:
tempFile should be a (file) |
Methods inherited from scala.Function1 | |
scala.Function1.toString, scala.Function1.compose, scala.Function1.andThen |
Methods inherited from AnyRef | |
getClass, hashCode, equals, clone, notify, notifyAll, wait, wait, wait, finalize, ==, !=, eq, ne, synchronized |
Methods inherited from Any | |
==, !=, isInstanceOf, asInstanceOf |
Method Details |
abstract
def
apply(objectWithProperty : T) : BePropertyMatchResult
Boolean
property on the specified object, objectWithProperty
, matches its
expected value, and report the result in
the returned BePropertyMatchResult
. The objectWithProperty
is
usually the value to the left of a should
or must
invocation. For example, tempFile
would be passed as the objectWithProperty
in:
tempFile should be a (file)
objectWithProperty -
the object with the Boolean
property against which to matchBePropertyMatchResult
that represents the result of the match
ScalaTest 1.0
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