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org.scalatest

OneInstancePerTest

trait OneInstancePerTest extends SuiteMixin

Trait that facilitates a style of testing in which each test is run in its own instance of the suite class to isolate each test from the side effects of the other tests in the suite.

Recommended Usage: Trait OneInstancePerTest is intended primarily to serve as a supertrait for ParallelTestExecution and the path traits, to facilitate porting JUnit tests to ScalaTest, and to make it easy for users who prefer JUnit's approach to isolation to obtain similar behavior in ScalaTest.

If you mix this trait into a Suite, you can initialize shared reassignable fixture variables as well as shared mutable fixture objects in the constructor of the class. Because each test will run in its own instance of the class, each test will get a fresh copy of the instance variables. This is the approach to test isolation taken, for example, by the JUnit framework. OneInstancePerTest can, therefore, be handy when porting JUnit tests to ScalaTest.

Here's an example of OneInstancePerTest being used in a FunSuite:

import org.scalatest.FunSuite
import org.scalatest.OneInstancePerTest
import collection.mutable.ListBuffer

class MySuite extends FunSuite with OneInstancePerTest {

  val builder = new StringBuilder("ScalaTest is ")
  val buffer = new ListBuffer[String]

  test("easy") {
    builder.append("easy!")
    assert(builder.toString === "ScalaTest is easy!")
    assert(buffer.isEmpty)
    buffer += "sweet"
  }

  test("fun") {
    builder.append("fun!")
    assert(builder.toString === "ScalaTest is fun!")
    assert(buffer.isEmpty)
  }
}

OneInstancePerTest is supertrait to ParallelTestExecution, in which running each test in its own instance is intended to make it easier to write suites of tests that run in parallel (by reducing the likelihood of concurrency bugs in those suites.) OneInstancePerTest is also supertrait to the path traits, path.FunSpec and path.FreeSpec, to make it obvious these traits run each test in a new, isolated instance.

For the details on how OneInstancePerTest works, see the documentation for methods runTests and runTest, which this trait overrides.

Self Type
OneInstancePerTest with Suite
Source
OneInstancePerTest.scala
Linear Supertypes
SuiteMixin, AnyRef, Any
Known Subclasses
ParallelTestExecution, RandomTestOrder, FreeSpec, FreeSpecLike, FunSpec, FunSpecLike
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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 def run(testName: Option[String], args: Args): Status

    Runs this suite of tests.

    Runs this suite of tests.

    testName

    an optional name of one test to execute. If None, all relevant tests should be executed. I.e., None acts like a wildcard that means execute 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
    SuiteMixin
    Exceptions thrown

    NullArgumentException if any passed parameter is null.

  5. 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
  6. 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
  7. 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
  8. 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
  9. 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
  10. 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 newInstance: Suite with OneInstancePerTest

    Construct a new instance of this Suite.

    Construct a new instance of this Suite.

    This trait's implementation of runTests invokes this method to create a new instance of this Suite for each test. This trait's implementation of this method uses reflection to call this.getClass.newInstance. This approach will succeed only if this Suite's class has a public, no-arg constructor. In most cases this is likely to be true, because to be instantiated by ScalaTest's Runner a Suite needs a public, no-arg constructor. However, this will not be true of any Suite defined as an inner class of another class or trait, because every constructor of an inner class type takes a reference to the enclosing instance. In such cases, and in cases where a Suite class is explicitly defined without a public, no-arg constructor, you will need to override this method to construct a new instance of the Suite in some other way.

    Here's an example of how you could override newInstance to construct a new instance of an inner class:

    import org.scalatest.Suite

class Outer {
  class InnerSuite extends Suite with OneInstancePerTest {
    def testOne() {}
    def testTwo() {}
    override def newInstance = new InnerSuite
  }
}