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 the BeMatcher's apply method. The result is a MatchResult.
A BeMatcher is, therefore, a function from the specified type, T, to a MatchResult.
Although BeMatcher
and Matcher represent very similar concepts, they have no inheritance relationship
because Matcher is intended for use right after should or must
whereas BeMatcher is intended for use right after be.
As an example, you could create BeMatcher[Int]
called odd that would match any odd Int, and one called even that would match
any even Int.
Given this pair of BeMatchers, you could check whether an Int was odd or even with expressions like:
num should be (odd) num should not be (even)
Here's is how you might define the odd and even BeMatchers:
trait CustomMatchers { class OddMatcher extends BeMatcher[Int] {
def apply(left: Int) =
MatchResult(
left % 2 == 1,
left.toString + " was even",
left.toString + " was odd"
)
}
val odd = new OddMatcher
val even = not (odd)
}
// Make them easy to import with:
// import CustomMatchers._
object CustomMatchers extends CustomMatchers
These BeMatchers are defined inside a trait to make them easy to mix into any
suite or spec that needs them.
The CustomMatchers companion object exists to make it easy to bring the
BeMatchers 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 odd and even:
class DoubleYourPleasureSuite extends FunSuite with MustMatchers with CustomMatchers { def doubleYourPleasure(i: Int): Int = i * 2
test("The doubleYourPleasure method must return proper odd or even values")
val evenNum = 2
evenNum must be (even)
doubleYourPleasure(evenNum) must be (even)
val oddNum = 3
oddNum must be (odd)
doubleYourPleasure(oddNum) must be (odd) // This will fail
}
}
The last assertion in the above test will fail with this failure message:
6 was even
For more information on MatchResult and the meaning of its fields, please
see the documentation for MatchResult. To understand why BeMatcher
is contravariant in its type parameter, see the section entitled "Matcher's variance" in the
documentation for Matcher.
o != arg0 is the same as !(o == (arg0)).
o != arg0 is the same as !(o == (arg0)).
the object to compare against this object for dis-equality.
false if the receiver object is equivalent to the argument; true otherwise.
o == arg0 is the same as if (o eq null) arg0 eq null else o.equals(arg0).
o == arg0 is the same as if (o eq null) arg0 eq null else o.equals(arg0).
the object to compare against this object for equality.
true if the receiver object is equivalent to the argument; false otherwise.
o == arg0 is the same as o.equals(arg0).
o == arg0 is the same as o.equals(arg0).
the object to compare against this object for equality.
true if the receiver object is equivalent to the argument; false otherwise.
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.
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
This method is used to cast the receiver object to be of type T0.
This method is used to cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression
1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression
List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as
part of compilation it is not possible to check whether the contents of the list are of the requested typed.
the receiver object.
This method creates and returns a copy of the receiver object.
This method creates and returns a copy of the receiver object.
The default implementation of the clone method is platform dependent.
a copy of the receiver object.
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)
This method is used to test whether the argument (arg0) is a reference to the
receiver object (this).
This method is used to test whether the argument (arg0) is a reference to the
receiver object (this).
The eq method implements an [http://en.wikipedia.org/wiki/Equivalence_relation equivalence relation] on
non-null instances of AnyRef:
* It is reflexive: for any non-null instance x of type AnyRef, x.eq(x) returns true.
* It is symmetric: for any non-null instances x and y of type AnyRef, x.eq(y) returns true if and
only if y.eq(x) returns true.
* It is transitive: for any non-null instances x, y, and z of type AnyRef if x.eq(y) returns true
and y.eq(z) returns true, then x.eq(z) returns true.
Additionally, the eq method has three other properties.
* It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of
x.eq(y) consistently returns true or consistently returns false.
* For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
* null.eq(null) returns true.
When overriding the equals or hashCode methods, it is important to ensure that their behavior is
consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they
should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
the object to compare against this object for reference equality.
true if the argument is a reference to the receiver object; false otherwise.
This method is used to compare the receiver object (this) with the argument object (arg0) for equivalence.
This method is used to compare the receiver object (this) with the argument object (arg0) for equivalence.
The default implementations of this method is an [http://en.wikipedia.org/wiki/Equivalence_relation equivalence
relation]:
* It is reflexive: for any instance x of type Any, x.equals(x) should return true.
* It is symmetric: for any instances x and y of type Any, x.equals(y) should return true if and
only if y.equals(x) returns true.
* It is transitive: for any instances x, y, and z of type AnyRef if x.equals(y) returns true and
y.equals(z) returns true, then x.equals(z) should return true.
If you override this method, you should verify that your implementation remains an equivalence relation.
Additionally, when overriding this method it is often necessary to override hashCode to ensure that objects
that are "equal" (o1.equals(o2) returns true) hash to the same scala.Int
(o1.hashCode.equals(o2.hashCode)).
the object to compare against this object for equality.
true if the receiver object is equivalent to the argument; false otherwise.
This method is called by the garbage collector on the receiver object when garbage collection determines that there are no more references to the object.
This method is called by the garbage collector on the receiver object when garbage collection determines that there are no more references to the object.
The details of when and if the finalize method are invoked, as well as the interaction between finalize
and non-local returns and exceptions, are all platform dependent.
Returns a representation that corresponds to the dynamic class of the receiver object.
Returns a representation that corresponds to the dynamic class of the receiver object.
The nature of the representation is platform dependent.
a representation that corresponds to the dynamic class of the receiver object.
Returns a hash code value for the object.
Returns a hash code value for the object.
The default hashing algorithm is platform dependent.
Note that it is allowed for two objects to have identical hash codes (o1.hashCode.equals(o2.hashCode)) yet
not be equal (o1.equals(o2) returns false). A degenerate implementation could always return 0.
However, it is required that if two objects are equal (o1.equals(o2) returns true) that they have
identical hash codes (o1.hashCode.equals(o2.hashCode)). Therefore, when overriding this method, be sure
to verify that the behavior is consistent with the equals method.
the hash code value for the object.
This method is used to test whether the dynamic type of the receiver object is T0.
This method is used to test whether the dynamic type of the receiver object is T0.
Note that the test result of the test is modulo Scala's erasure semantics. Therefore the expression
1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will
return true. In the latter example, because the type argument is erased as part of compilation it is not
possible to check whether the contents of the list are of the requested typed.
true if the receiver object is an instance of erasure of type T0; false otherwise.
o.ne(arg0) is the same as !(o.eq(arg0)).
o.ne(arg0) is the same as !(o.eq(arg0)).
the object to compare against this object for reference dis-equality.
false if the argument is not a reference to the receiver object; true otherwise.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up a single thread that is waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
Wakes up all threads that are waiting on the receiver object's monitor.
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
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:trait CustomMatchers {class OddMatcher extends BeMatcher[Int] { def apply(left: Int) = MatchResult( left % 2 == 1, left.toString + " was even", left.toString + " was odd" ) } val odd = new OddMatcher val even = not (odd) }
// Make them easy to import with: // import CustomMatchers._ object CustomMatchers extends CustomMatchers
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:class DoubleYourPleasureSuite extends FunSuite with MustMatchers with CustomMatchers {def doubleYourPleasure(i: Int): Int = i * 2
test("The doubleYourPleasure method must return proper odd or even values")
val evenNum = 2 evenNum must be (even) doubleYourPleasure(evenNum) must be (even)
val oddNum = 3 oddNum must be (odd) doubleYourPleasure(oddNum) must be (odd) // This will fail } }
The last assertion in the above test will fail with this failure message:
For 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.