org.scalatest.exceptions.ModifiableMessage.scala Maven / Gradle / Ivy
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/*
* Copyright 2001-2009 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.exceptions
/**
* Trait implemented by exception types that can modify their detail message.
*
*
* This trait facilitates the withClue construct provided by trait
* Assertions. This construct enables extra information (or "clues") to
* be included in the detail message of a thrown exception. Although both
* assert and expect provide a way for a clue to be
* included directly, intercept and ScalaTest matcher expressions
* do not. Here's an example of clues provided directly in assert:
*
*
*
* assert(1 + 1 === 3, "this is a clue")
*
*
*
* and in expect:
*
*
*
* expect(3, "this is a clue") { 1 + 1 }
*
*
*
* The exceptions thrown by the previous two statements will include the clue
* string, "this is a clue", in the exceptions detail message.
* To get the same clue in the detail message of an exception thrown
* by a failed intercept call requires using withClue:
*
*
*
* withClue("this is a clue") {
* intercept[IndexOutOfBoundsException] {
* "hi".charAt(-1)
* }
* }
*
*
*
* Similarly, to get a clue in the exception resulting from an exception arising out
* of a ScalaTest matcher expression, you need to use withClue. Here's
* an example:
*
*
*
* withClue("this is a clue") {
* 1 + 1 should be === 3
* }
*
*
*
* Exception types that mix in this trait have a modifyMessage method, which
* returns an exception identical to itself, except with the detail message option replaced with
* the result of invoking the passed function, supplying the current detail message option
* as the lone String parameter.
*
*/
trait ModifiableMessage[T <: Throwable] { this: Throwable =>
/**
* Returns an instance of this exception's class, identical to this exception,
* except with the detail message option replaced with
* the result of invoking the passed function, fun, supplying the current detail message option
* as the lone Option[String] parameter.
*
*
* Implementations of this method may either mutate this exception or return
* a new instance with the revised detail message.
*
*
* @param fun A function that returns the new detail message option given the old one.
*/
def modifyMessage(fun: Option[String] => Option[String]): T
}