org.scalatest.fixture.WordSpec.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.WordSpec that can pass a fixture object into its tests.
*
*
* Recommended Usage:
* Use class fixture.WordSpec in situations for which WordSpec
* would be a good choice, when all or most tests need the same fixture objects
* that must be cleaned up afterwards. Note: fixture.WordSpec is intended for use in special situations, with class WordSpec used for general needs. For
* more insight into where fixture.WordSpec fits in the big picture, see the withFixture(OneArgTest) subsection of the Shared fixtures section in the documentation for class WordSpec.
*
*
*
* Class fixture.WordSpec behaves similarly to class org.scalatest.WordSpec, 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(OneArgTest), passing
* in the test code to run via the OneArgTest argument. The withFixture(OneArgTest) 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.WordSpec:
*
*
*
* - 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.)
*
*
*
* 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(file: File, writer: FileWriter)
*
*
*
* 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.wordspec.oneargtest
*
* import org.scalatest.fixture
* import java.io._
*
* class ExampleSpec extends fixture.WordSpec {
*
* case class FixtureParam(file: File, writer: FileWriter)
*
* def withFixture(test: OneArgTest) = {
*
* // create the fixture
* val file = File.createTempFile("hello", "world")
* val writer = new FileWriter(file)
* val theFixture = FixtureParam(file, writer)
*
* try {
* writer.write("ScalaTest is ") // set up the fixture
* withFixture(test.toNoArgTest(theFixture)) // "loan" the fixture to the test
* }
* finally writer.close() // clean up the fixture
* }
*
* "Testing" should {
* "be easy" in { f =>
* f.writer.write("easy!")
* f.writer.flush()
* assert(f.file.length === 18)
* }
*
* "be fun" in { f =>
* f.writer.write("fun!")
* f.writer.flush()
* assert(f.file.length === 17)
* }
* }
* }
*
*
*
* If a test fails, the OneArgTest function will result in a [[org.scalatest.Failed Failed]] wrapping the exception describing the failure.
* To ensure clean up happens 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.
*
*
* Sharing fixtures across classes
*
*
* If multiple test classes need the same fixture, you can define the FixtureParam and withFixture(OneArgTest) implementations
* in a trait, then mix that trait into the test classes that need it. For example, if your application requires a database and your integration tests
* use that database, you will likely have many test classes that need a database fixture. You can create a "database fixture" trait that creates a
* database with a unique name, passes the connector into the test, then removes the database once the test completes. This is shown in the following example:
*
*
*
* package org.scalatest.examples.fixture.wordspec.sharing
*
* import java.util.concurrent.ConcurrentHashMap
* import org.scalatest.fixture
* import DbServer._
* import java.util.UUID.randomUUID
*
* object DbServer { // Simulating a database server
* type Db = StringBuffer
* private val databases = new ConcurrentHashMap[String, Db]
* def createDb(name: String): Db = {
* val db = new StringBuffer
* databases.put(name, db)
* db
* }
* def removeDb(name: String) {
* databases.remove(name)
* }
* }
*
* trait DbFixture { this: fixture.Suite =>
*
* type FixtureParam = Db
*
* // Allow clients to populate the database after
* // it is created
* def populateDb(db: Db) {}
*
* def withFixture(test: OneArgTest) = {
* val dbName = randomUUID.toString
* val db = createDb(dbName) // create the fixture
* try {
* populateDb(db) // setup the fixture
* withFixture(test.toNoArgTest(db)) // "loan" the fixture to the test
* }
* finally removeDb(dbName) // clean up the fixture
* }
* }
*
* class ExampleSpec extends fixture.WordSpec with DbFixture {
*
* override def populateDb(db: Db) { // setup the fixture
* db.append("ScalaTest is ")
* }
*
* "Testing" should {
* "should be easy" in { db =>
* db.append("easy!")
* assert(db.toString === "ScalaTest is easy!")
* }
*
* "should be fun" in { db =>
* db.append("fun!")
* assert(db.toString === "ScalaTest is fun!")
* }
* }
*
* // This test doesn't need a Db
* "Test code" should {
* "should be clear" in { () =>
* val buf = new StringBuffer
* buf.append("ScalaTest code is ")
* buf.append("clear!")
* assert(buf.toString === "ScalaTest code is clear!")
* }
* }
* }
*
*
*
* Often when you create fixtures in a trait like DbFixture, you'll still need to enable individual test classes
* to "setup" a newly created fixture before it gets passed into the tests. A good way to accomplish this is to pass the newly
* created fixture into a setup method, like populateDb in the previous example, before passing it to the test
* function. Classes that need to perform such setup can override the method, as does ExampleSpec.
*
*
*
* If a test doesn't need the fixture, you can indicate that by providing a no-arg instead of a one-arg function, as is done in the
* third test in the previous example, “Test code should be clear”. In other words, instead of starting your function literal
* with something like “db =>”, you'd start it with “() =>”. For such tests, runTest
* will not invoke withFixture(OneArgTest). It will instead directly invoke withFixture(NoArgTest).
*
*
*
* Both examples shown above demonstrate the technique of giving each test its own "fixture sandbox" to play in. When your fixtures
* involve external side-effects, like creating files or databases, it is a good idea to give each file or database a unique name as is
* done in these examples. This keeps tests completely isolated, allowing you to run them in parallel if desired. You could mix
* ParallelTestExecution into either of these ExampleSpec classes, and the tests would run in parallel just fine.
*
*
* @author Bill Venners
*/
@Finders(Array("org.scalatest.finders.WordSpecFinder"))
abstract class WordSpec extends WordSpecLike {
/**
* 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)
}