org.scalatest.matchers

BePropertyMatcher

trait BePropertyMatcher[-T] extends (T) ⇒ BePropertyMatchResult

Trait extended by matcher objects, which may appear after the word be, 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 BePropertyMatchers:

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 BePropertyMatchers 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 vals 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.

Inherits

  1. Function1
  2. AnyRef
  3. Any

Value Members

  1. def andThen[A](g: (BePropertyMatchResult) ⇒ A): (T) ⇒ A

  2. def 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

    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)
    

    objectWithProperty

    the object with the Boolean property against which to match

    returns

    the BePropertyMatchResult that represents the result of the match

    attributes: abstract
  3. def compose[A](g: (A) ⇒ T): (A) ⇒ BePropertyMatchResult

  4. def equals(arg0: Any): Boolean

    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 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 Int (o1.hashCode.equals(o2.hashCode)).

    arg0

    the object to compare against this object for equality.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    definition classes: AnyRef ⇐ Any
  5. def hashCode(): Int

    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.

    definition classes: AnyRef ⇐ Any
  6. def toString(): String

    Returns a string representation of the object

    Returns a string representation of the object.

    The default representation is platform dependent.

    definition classes: Function1 ⇐ AnyRef ⇐ Any