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.
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:
list should equal (List(1, 2, 3))
The equal (List(1, 2, 3)) expression results in a matcher that holds a reference to the
right value, List(1, 2, 3). The should method invokes applyon this matcher, passing in list, which is therefore the "left" value. The
matcher will compare the list (the left value) with List(1, 2, 3) (the right
value), and report the result in the returned MatchResult.
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 expression1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expressionList(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.
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 finalizeand 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 expression1.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 objects that can match a value of the specified type. The value to match is passed to the matcher's
applymethod. The result is aMatchResult. A matcher is, therefore, a function from the specified type,T, to aMatchResult.Creating custom matchers
If none of the built-in matcher syntax satisfy a particular need you have, you can create custom
Matchers that allow you to place your own syntax directly aftershouldormust. For example, classjava.io.Filehas a methodexists, which indicates whether a file of a certain path and name exists. Because theexistsmethod takes no parameters and returnsBoolean, you can call it usingbewith a symbol orBePropertyMatcher, yielding assertions like:file should be ('exists) // using a symbol file should be (inExistance) // using a BePropertyMatcherAlthough these expressions will achieve your goal of throwing a
TestFailedExceptionif the file does not exist, they don't produce the most readable code because the English is either incorrect or awkward. In this case, you might want to create a customMatcher[java.io.File]namedexist, which you could then use to write expressions like:// using a plain-old Matcher file should exist file should not (exist) file should (exist and have ('name ("temp.txt")))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:
trait CustomMatchers {class FileExistsMatcher extends Matcher[java.io.File] {
def apply(left: java.io.File) = {
val fileOrDir = if (left.isFile) "file" else "directory"
val failureMessageSuffix = fileOrDir + " named " + left.getName + " did not exist"
val negatedFailureMessageSuffix = fileOrDir + " named " + left.getName + " existed"
MatchResult( left.exists, "The " + failureMessageSuffix, "The " + negatedFailureMessageSuffix, "the " + failureMessageSuffix, "the " + negatedFailureMessageSuffix ) } }
val exist = new FileExistsMatcher }
// Make them easy to import with: // import CustomMatchers._ object CustomMatchers extends CustomMatchers
Note: the
CustomMatcherscompanion object exists to make it easy to bring the matchers 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.This trait contains one matcher class,
FileExistsMatcher, and avalnamedexistthat refers to an instance ofFileExistsMatcher. Because the class extendsMatcher[java.io.File], the compiler will only allow it be used to match against instances ofjava.io.File. A matcher must declare anapplymethod that takes the type decared inMatcher's type parameter, in this casejava.io.File. The apply method will return aMatchResultwhosematchesfield will indicate whether the match succeeded. ThefailureMessagefield will provide a programmer-friendly error message indicating, in the event of a match failure, what caused the match to fail.The
FileExistsMatchermatcher in this example determines success by callingexistson the passedjava.io.File. It does this in the first argument passed to theMatchResultfactory method:In other words, if the file exists, this matcher matches. The next argument to
MatchResult's factory method produces the failure message string:If the passed
java.io.Fileis a file (not a directory) and has the nametemp.txt, for example, the failure message would be:For more information on the fields in a
MatchResult, including the subsequent three fields that follow the failure message, please see the documentation forMatchResult.Given the
CustomMatcherstrait as defined above, you can use theexistsyntax in any suite or spec in which you mix in the trait:class ExampleSpec extends Spec with ShouldMatchers with CustomMatchers {describe("A temp file") {
it("should be created and deleted") {
val tempFile = java.io.File.createTempFile("delete", "me")
try { // At this point the temp file should exist tempFile should exist } finally { tempFile.delete() }
// At this point it should not exist tempFile should not (exist) } } }
Note that when you use custom
Matchers, you will need to put parentheses around the custom matcher when if followsnot, as shown in the last assertion above:tempFile should not (exist).Matcher's variance
Matcheris contravariant in its type parameter,T, to make its use more flexible. As an example, consider the hierarchy:Given an orange:
The expression "
orange should" will, via an implicit conversion inShouldMatchers, result in an object that has ashouldmethod that takes aMatcher[Orange]. If the static type of the matcher being passed toshouldisMatcher[Valencia]it shouldn't (and won't) compile. The reason it shouldn't compile is that the left value is anOrange, but not necessarily aValencia, and aMatcher[Valencia]only knows how to match against aValencia. The reason it won't compile is given thatMatcheris contravariant in its type parameter,T, aMatcher[Valencia]is not a subtype ofMatcher[Orange].By contrast, if the static type of the matcher being passed to
shouldisMatcher[Fruit], it should (and will) compile. The reason it should compile is that given the left value is anOrange, it is also aFruit, and aMatcher[Fruit]knows how to match againstFruits. The reason it will compile is that given thatMatcheris contravariant in its type parameter,T, aMatcher[Fruit]is indeed a subtype ofMatcher[Orange].authors:
Bill Venners