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org.scalatest

BeforeAndAfter

trait BeforeAndAfter extends SuiteMixin

Trait that can be mixed into suites that need code executed before and after running each test.

Recommended Usage: Use trait BeforeAndAfter when you need to perform the same side-effects before and/or after tests, rather than at the beginning or end of tests. Note: For more insight into where BeforeAndAfter fits into the big picture, see the Shared fixtures section in the documentation for your chosen style trait.

A test fixture is composed of the objects and other artifacts (files, sockets, database connections, etc.) tests use to do their work. When multiple tests need to work with the same fixtures, it is important to try and avoid duplicating the fixture code across those tests. The more code duplication you have in your tests, the greater drag the tests will have on refactoring the actual production code. Trait BeforeAndAfter offers one way to eliminate such code duplication: a before clause that will register code to be run before each test, and an after clause that will register code to be run after.

Here's an example:

package org.scalatest.examples.flatspec.beforeandafter

import org.scalatest._
import collection.mutable.ListBuffer

class ExampleSpec extends FlatSpec with BeforeAndAfter {

  val builder = new StringBuilder
  val buffer = new ListBuffer[String]

  before {
    builder.append("ScalaTest is ")
  }

  after {
    builder.clear()
    buffer.clear()
  }

  "Testing" should "be easy" in {
    builder.append("easy!")
    assert(builder.toString === "ScalaTest is easy!")
    assert(buffer.isEmpty)
    buffer += "sweet"
  }

  it should "be fun" in {
    builder.append("fun!")
    assert(builder.toString === "ScalaTest is fun!")
    assert(buffer.isEmpty)
  }
}

The before and after methods can each only be called once per Suite, and cannot be invoked after run has been invoked. If either of the registered before or after functions complete abruptly with an exception, it will be reported as an aborted suite and no more tests will be attempted in that suite.

Note that the only way before and after code can communicate with test code is via some side-effecting mechanism, commonly by reassigning instance vars or by changing the state of mutable objects held from instance vals (as in this example). If using instance vars or mutable objects held from instance vals you wouldn't be able to run tests in parallel in the same instance of the test class unless you synchronized access to the shared, mutable state. This is why ScalaTest's ParallelTestExecution trait extends OneInstancePerTest. By running each test in its own instance of the class, each test has its own copy of the instance variables, so you don't need to synchronize. Were you to mix ParallelTestExecution into the ExampleSuite above, the tests would run in parallel just fine without any synchronization needed on the mutable StringBuilder and ListBuffer[String] objects.

Although BeforeAndAfter provides a minimal-boilerplate way to execute code before and after tests, it isn't designed to enable stackable traits, because the order of execution would be non-obvious. If you want to factor out before and after code that is common to multiple test suites, you should use trait BeforeAndAfterEach instead.

The advantage this trait has over BeforeAndAfterEach is that its syntax is more concise. The main disadvantage is that it is not stackable, whereas BeforeAndAfterEach is. I.e., you can write several traits that extend BeforeAndAfterEach and provide beforeEach methods that include a call to super.beforeEach, and mix them together in various combinations. By contrast, only one call to the before registration function is allowed in a suite or spec that mixes in BeforeAndAfter. In addition, BeforeAndAfterEach allows you to access the config map and test name via the TestData passed to its beforeEach and afterEach methods, whereas BeforeAndAfter gives you no access to the config map.

Self Type
BeforeAndAfter with Suite
Source
BeforeAndAfter.scala
Linear Supertypes
SuiteMixin, AnyRef, Any
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Abstract Value Members

  1. abstract def expectedTestCount(filter: Filter): Int

    The total number of tests that are expected to run when this Suite's run method is invoked.

    The total number of tests that are expected to run when this Suite's run method is invoked.

    filter

    a Filter with which to filter tests to count based on their tags

    Definition Classes
    SuiteMixin
  2. abstract def nestedSuites: IndexedSeq[Suite]

    An immutable IndexedSeq of this SuiteMixin object's nested Suites.

    An immutable IndexedSeq of this SuiteMixin object's nested Suites. If this SuiteMixin contains no nested Suites, this method returns an empty IndexedSeq.

    Definition Classes
    SuiteMixin
  3. abstract def rerunner: Option[String]

    The fully qualified name of the class that can be used to rerun this suite.

    The fully qualified name of the class that can be used to rerun this suite.

    Definition Classes
    SuiteMixin
  4. abstract val styleName: String

    This suite's style name.

    This suite's style name.

    This lifecycle method provides a string that is used to determine whether this suite object's style is one of the chosen styles for the project.

    Definition Classes
    SuiteMixin
  5. abstract def suiteId: String

    A string ID for this Suite that is intended to be unique among all suites reported during a run.

    A string ID for this Suite that is intended to be unique among all suites reported during a run.

    The suite ID is intended to be unique, because ScalaTest does not enforce that it is unique. If it is not unique, then you may not be able to uniquely identify a particular test of a particular suite. This ability is used, for example, to dynamically tag tests as having failed in the previous run when rerunning only failed tests.

    returns

    this Suite object's ID.

    Definition Classes
    SuiteMixin
  6. abstract def suiteName: String

    A user-friendly suite name for this Suite.

    A user-friendly suite name for this Suite.

    This trait's implementation of this method returns the simple name of this object's class. This trait's implementation of runNestedSuites calls this method to obtain a name for Reports to pass to the suiteStarting, suiteCompleted, and suiteAborted methods of the Reporter.

    returns

    this Suite object's suite name.

    Definition Classes
    SuiteMixin
  7. abstract def tags: Map[String, Set[String]]

    A Map whose keys are String names of tagged tests and whose associated values are the Set of tag names for the test.

    A Map whose keys are String names of tagged tests and whose associated values are the Set of tag names for the test. If a test has no associated tags, its name does not appear as a key in the returned Map. If this Suite contains no tests with tags, this method returns an empty Map.

    Subclasses may override this method to define and/or discover tags in a custom manner, but overriding method implementations should never return an empty Set as a value. If a test has no tags, its name should not appear as a key in the returned Map.

    Definition Classes
    SuiteMixin
  8. abstract def testDataFor(testName: String, theConfigMap: ConfigMap): TestData

    Provides a TestData instance for the passed test name, given the passed config map.

    Provides a TestData instance for the passed test name, given the passed config map.

    This method is used to obtain a TestData instance to pass to withFixture(NoArgTest) and withFixture(OneArgTest) and the beforeEach and afterEach methods of trait BeforeAndAfterEach.

    testName

    the name of the test for which to return a TestData instance

    theConfigMap

    the config map to include in the returned TestData

    returns

    a TestData instance for the specified test, which includes the specified config map

    Definition Classes
    SuiteMixin
  9. abstract def testNames: Set[String]

    A Set of test names.

    A Set of test names. If this Suite contains no tests, this method returns an empty Set.

    Although subclass and subtrait implementations of this method may return a Set whose iterator produces String test names in a well-defined order, the contract of this method does not required a defined order. Subclasses are free to implement this method and return test names in either a defined or undefined order.

    Definition Classes
    SuiteMixin

Concrete Value Members

  1. def run(testName: Option[String], args: Args): Status

    This trait's implementation of run sets a flag indicating run has been invoked, after which any invocation to before or after will complete abruptly with a NotAllowedException.

    This trait's implementation of run sets a flag indicating run has been invoked, after which any invocation to before or after will complete abruptly with a NotAllowedException.

    testName

    an optional name of one test to run. If None, all relevant tests should be run. I.e., None acts like a wildcard that means run all relevant tests in this Suite.

    args

    the Args for this run

    returns

    a Status object that indicates when all tests and nested suites started by this method have completed, and whether or not a failure occurred.

    Definition Classes
    BeforeAndAfter → SuiteMixin