org.scalatest.AppendedClues.scala Maven / Gradle / Ivy
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/*
* Copyright 2001-2011 Artima, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.scalatest
import exceptions.ModifiableMessage
/**
* Trait providing an implicit conversion that allows clues to be placed after a block of code.
*
*
* You can use the withClue construct provided by Assertions, which is
* extended by every style trait in ScalaTest, to add extra information to reports of failed or canceled tests.
* The withClue from Assertions places the "clue string" at the front, both
* in the code and in the resulting message:
*
*
* withClue("This is a prepended clue;") {
* 1 + 1 should equal (3)
* }
*
*
*
* The above expression will yield the failure message:
*
*
*
* This is a prepended clue; 2 did not equal 3
*
*
*
* If you mix in this trait, or import its members via its companion object, you can alternatively place
* the clue string at the end, like this:
*
*
*
* { 1 + 1 should equal (3) } withClue "now the clue comes after"
*
*
*
* The above expression will yield the failure message:
*
*
*
* 2 did not equal 3 now the clue comes after
*
*
*
* If no space is already present, either at the beginning of the clue string or at the end
* of the current message, a space will be placed between the two, unless the clue string
* starts with one of the punctuation characters: comma (,), period (.),
* or semicolon (;). For example, the failure message in the above example
* includes an extra space inserted between 3 and now.
*
*
*
* By contrast this code, which has a clue string starting with comma:
*
*
*
* { 1 + 1 should equal (3) } withClue ", now the clue comes after"
*
*
*
* Will yield a failure message with no extra inserted space:
*
*
*
* 2 did not equal 3, now the clue comes after
*
*
*
* The withClue method will only append the clue string to the detail
* message of exception types that mix in the ModifiableMessage trait.
* See the documentation for ModifiableMessage for more
* information.
*
*
*
* Note: the reason this functionality is not provided by Assertions directly, like the
* prepended withClue construct, is because appended clues require an implicit conversion.
* ScalaTest only gives you one implicit conversion by default in any test class to minimize the
* potential for conflicts with other implicit conversions you may be using. All other implicit conversions,
* including the one provided by this trait, you must explicitly invite into your code through inheritance
* or an import.
*
*
* @author Bill Venners
*/
trait AppendedClues {
/**
* Class that provides a withClue method that appends clue strings to any
* ModifiableMessage exception
* thrown by the passed by-name parameter.
*
* @author Bill Venners
*/
class Clueful[T](fun: => T) {
/**
* Executes the block of code passed as the constructor parameter to this Clueful, and, if it
* completes abruptly with a ModifiableMessage exception,
* appends the "clue" string passed to this method to the end of the detail message
* of that thrown exception, then rethrows it. If clue does not begin in a white space
* character or one of the punctuation characters: comma (,),
* period (.), or semicolon (;), one space will be added
* between it and the existing detail message (unless the detail message is
* not defined).
*
*
* This method allows you to add more information about what went wrong that will be
* reported when a test fails or cancels. For example, this code:
*
*
*
* { 1 + 1 should equal (3) } withClue ", not even for very large values of 1"
*
*
*
* Would yield a TestFailed exception whose message would be:
*
*
*
* 2 did not equal 3, not even for very large values of 1
*
*
* @throws NullPointerException if the passed clue is null
*/
def withClue(clue: Any): T = {
if (clue == null)
throw new NullPointerException("clue was null")
def append(currentMessage: Option[String]) =
currentMessage match {
case Some(msg) =>
// clue.toString.head is guaranteed to work, because append() only called if clue.toString != ""
val firstChar = clue.toString.head
if (firstChar.isWhitespace || firstChar == '.' || firstChar == ',' || firstChar == ';')
Some(msg + clue.toString)
else
Some(msg + " " + clue.toString)
case None => Some(clue.toString)
}
try {
fun
}
catch {
case e: ModifiableMessage[_] =>
if (clue.toString != "")
throw e.modifyMessage(append)
else
throw e
}
}
}
/**
* Implicit conversion that allows clues to be place after a block of code.
*/
implicit def convertToClueful[T](fun: => T) = new Clueful(fun)
}
/**
* Companion object that facilitates the importing of AppendedClues members as
* an alternative to mixing it in. One use case is to import AppendedClues
* members so you can use them in the Scala interpreter.
*/
object AppendedClues extends AppendedClues