org.scalatest.fixture.PropSpec.scala Maven / Gradle / Ivy
/*
* Copyright 2001-2013 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.fixture
import org.scalatest._
/**
* A sister class to org.scalatest.PropSpec that can pass a fixture object into its tests.
*
*
* Recommended Usage:
* Use class fixture.PropSpec in situations for which PropSpec
* would be a good choice, when all or most tests need the same fixture objects
* that must be cleaned up afterwards. Note: fixture.PropSpec is intended for use in special
* situations, with class PropSpec used for general needs. For
* more insight into where fixture.PropSpec fits in the big picture, see
* the withFixture(OneArgTest) subsection of
* the Shared fixtures section in the documentation for class PropSpec.
*
*
*
* Class fixture.PropSpec behaves similarly to class org.scalatest.PropSpec, except that tests may have a
* fixture parameter. The type of the
* fixture parameter is defined by the abstract FixtureParam type, which is a member of this class.
* This class also has an abstract withFixture method. This withFixture method
* takes a OneArgTest, which is a nested trait defined as a member of this class.
* OneArgTest has an apply method that takes a FixtureParam.
* This apply method is responsible for running a test.
* This class's runTest method delegates the actual running of each test to withFixture, passing
* in the test code to run via the OneArgTest argument. The withFixture method (abstract in this class) is responsible
* for creating the fixture argument and passing it to the test function.
*
*
*
* Subclasses of this class must, therefore, do three things differently from a plain old org.scalatest.PropSpec:
*
*
*
* - define the type of the fixture parameter by specifying type
FixtureParam
* - define the
withFixture(OneArgTest) method
* - write tests that take a fixture parameter
* - (You can also define tests that don't take a fixture parameter.)
*
*
*
* Here's an example:
*
*
*
* package org.scalatest.examples.fixture.propspec
*
* import org.scalatest._
* import prop.PropertyChecks
* import java.io._
*
* class ExampleSpec extends fixture.PropSpec with PropertyChecks with Matchers {
*
* // 1. define type FixtureParam
* type FixtureParam = FileReader
*
* // 2. define the withFixture method
* def withFixture(test: OneArgTest) = {
*
* val FileName = "TempFile.txt"
*
* // Set up the temp file needed by the test
* val writer = new FileWriter(FileName)
* try {
* writer.write("Hello, test!")
* }
* finally {
* writer.close()
* }
*
* // Create the reader needed by the test
* val reader = new FileReader(FileName)
*
* try {
* // Run the test using the temp file
* test(reader)
* }
* finally {
* // Close and delete the temp file
* reader.close()
* val file = new File(FileName)
* file.delete()
* }
* }
*
* // 3. write property-based tests that take a fixture parameter
* // (Hopefully less contrived than the examples shown here.)
* property("can read from a temp file") { reader =>
* var builder = new StringBuilder
* var c = reader.read()
* while (c != -1) {
* builder.append(c.toChar)
* c = reader.read()
* }
* val fileContents = builder.toString
* forAll { (c: Char) =>
* whenever (c != 'H') {
* fileContents should not startWith c.toString
* }
* }
* }
*
* property("can read the first char of the temp file") { reader =>
* val firstChar = reader.read()
* forAll { (c: Char) =>
* whenever (c != 'H') {
* c should not equal firstChar
* }
* }
* }
*
* // (You can also write tests that don't take a fixture parameter.)
* property("can write tests that don't take the fixture") { () =>
* forAll { (i: Int) => i + i should equal (2 * i) }
* }
* }
*
*
*
* Note: to run the examples on this page, you'll need to include ScalaCheck on the classpath in addition to ScalaTest.
*
*
*
* In the previous example, withFixture creates and initializes a temp file, then invokes the test function,
* passing in a FileReader connected to that file. In addition to setting up the fixture before a test,
* the withFixture method also cleans it up afterwards. If you need to do some clean up
* that must happen even if a test fails, you should invoke the test function from inside a try block and do
* the cleanup in a finally clause, as shown in the previous example.
*
*
*
* If a test fails, the OneArgTest function will result in a [[org.scalatest.Failed Failed]] wrapping the
* exception describing the failure.
* The reason you must perform cleanup in a finally clause is that in case an exception propagates back through
* withFixture, the finally clause will ensure the fixture cleanup happens as that exception
* propagates back up the call stack to runTest.
*
*
*
* If a test doesn't need the fixture, you can indicate that by providing a no-arg instead of a one-arg function.
* In other words, instead of starting your function literal
* with something like “reader =>”, you'd start it with “() =>”, as is done
* in the third test in the above example. For such tests, runTest
* will not invoke withFixture(OneArgTest). It will instead directly invoke withFixture(NoArgTest).
*
*
*
* Passing multiple fixture objects
*
*
* If the fixture you want to pass into your tests consists of multiple objects, you will need to combine
* them into one object to use this class. One good approach to passing multiple fixture objects is
* to encapsulate them in a case class. Here's an example:
*
*
*
* case class FixtureParam(builder: StringBuilder, buffer: ListBuffer[String])
*
*
*
* To enable the stacking of traits that define withFixture(NoArgTest), it is a good idea to let
* withFixture(NoArgTest) invoke the test function instead of invoking the test
* function directly. To do so, you'll need to convert the OneArgTest to a NoArgTest. You can do that by passing
* the fixture object to the toNoArgTest method of OneArgTest. In other words, instead of
* writing “test(theFixture)”, you'd delegate responsibility for
* invoking the test function to the withFixture(NoArgTest) method of the same instance by writing:
*
*
*
* withFixture(test.toNoArgTest(theFixture))
*
*
*
* Here's a complete example:
*
*
*
* package org.scalatest.examples.fixture.propspec.multi
*
* import org.scalatest._
* import prop.PropertyChecks
* import scala.collection.mutable.ListBuffer
*
* class ExampleSpec extends fixture.PropSpec with PropertyChecks with Matchers {
*
* case class FixtureParam(builder: StringBuilder, buffer: ListBuffer[String])
*
* def withFixture(test: OneArgTest) = {
*
* // Create needed mutable objects
* val stringBuilder = new StringBuilder("ScalaTest is ")
* val listBuffer = new ListBuffer[String]
* val theFixture = FixtureParam(stringBuilder, listBuffer)
*
* // Invoke the test function, passing in the mutable objects
* withFixture(test.toNoArgTest(theFixture))
* }
*
* property("testing should be easy") { f =>
* f.builder.append("easy!")
* assert(f.builder.toString === "ScalaTest is easy!")
* assert(f.buffer.isEmpty)
* val firstChar = f.builder(0)
* forAll { (c: Char) =>
* whenever (c != 'S') {
* c should not equal firstChar
* }
* }
* f.buffer += "sweet"
* }
*
* property("testing should be fun") { f =>
* f.builder.append("fun!")
* assert(f.builder.toString === "ScalaTest is fun!")
* assert(f.buffer.isEmpty)
* val firstChar = f.builder(0)
* forAll { (c: Char) =>
* whenever (c != 'S') {
* c should not equal firstChar
* }
* }
* }
* }
*
*
* @author Bill Venners
*/
@Finders(Array("org.scalatest.finders.PropSpecFinder"))
abstract class PropSpec extends PropSpecLike {
/**
* Returns a user friendly string for this suite, composed of the
* simple name of the class (possibly simplified further by removing dollar signs if added by the Scala interpeter) and, if this suite
* contains nested suites, the result of invoking toString on each
* of the nested suites, separated by commas and surrounded by parentheses.
*
* @return a user-friendly string for this suite
*/
override def toString: String = Suite.suiteToString(None, this)
}