|
ScalaTest 1.0
|
|
org/scalatest/Assertions.scala]
final
class
Equalizer(left : Any)
extends AnyRef=== in assertions in tests. For example:
assert(a === b)
The benefit of using assert(a === b) rather than assert(a == b) is
that a TestFailedException produced by the former will include the values of a and b
in its detail message.
The implicit method that performs the conversion from Any to Equalizer is
convertToEqualizer in trait Assertions.
In case you're not familiar with how implicit conversions work in Scala, here's a quick explanation.
The convertToEqualizer method in Assertions is defined as an "implicit" method that takes an
Any, which means you can pass in any object, and it will convert it to an Equalizer.
The Equalizer has === defined. Most objects don't have === defined as a method
on them. Take two Strings, for example:
assert("hello" === "world")
Given this code, the Scala compiler looks for an === method on class String, because that's the class of
"hello". String doesn't define ===, so the compiler looks for an implicit conversion from
String to something that does have an === method, and it finds the convertToEqualizer method. It
then rewrites the code to this:
assert(convertToEqualizer("hello").===("world"))
So inside a Suite (which mixes in Assertions, === will work on anything. The only
situation in which the implicit conversion wouldn't
happen is on types that have an === method already defined.
The primary constructor takes one object, left, whose type is being converted to Equalizer. The left
value may be a null reference, because this is allowed by Scala's == operator.
left - An object to convert to Equalizer, which represents the left value of an assertion.| Method Summary | |
def
|
===
(right : Any) : scala.Option[java.lang.String]
The
=== operation compares this Equalizer's left value (passed
to the constructor, usually via an implicit conversion) with the passed right value
for equality as determined by the expression left == right.
If true, === returns None. Else, === returns
a Some whose String value indicates the left and right values. |
| Methods inherited from AnyRef | |
| getClass, hashCode, equals, clone, toString, notify, notifyAll, wait, wait, wait, finalize, ==, !=, eq, ne, synchronized |
| Methods inherited from Any | |
| ==, !=, isInstanceOf, asInstanceOf |
| Method Details |
def
===(right : Any) : scala.Option[java.lang.String]
=== operation compares this Equalizer's left value (passed
to the constructor, usually via an implicit conversion) with the passed right value
for equality as determined by the expression left == right.
If true, === returns None. Else, === returns
a Some whose String value indicates the left and right values.
In its typical usage, the Option[String] returned by === will be passed to one of two
of trait Assertion' overloaded assert methods. If None,
which indicates the assertion succeeded, assert will return normally. But if Some is passed,
which indicates the assertion failed, assert will throw a TestFailedException whose detail
message will include the String contained inside the Some, which in turn includes the
left and right values. This TestFailedException is typically embedded in a
Report and passed to a Reporter, which can present the left and right
values to the user.
|
ScalaTest 1.0
|
|