1. 13-Mar-16 Scalatest

2. Scalatest variants Scalatest is a testing framework inspired by JUnit Scalatest comes in various styles: FunSuite, FlatSpec, FunSpec, WordSpec, FreeSpec, Spec, PropSpec, and FeatureSpec Examples of these can be seen at http://www.scalatest.org/user_guide/selecting_a_style http://www.scalatest.org/user_guide/selecting_a_style The style I use (and talk about on these slides) is FunSuite, because it’s most like JUnit, but you are welcome to use whatever style you prefer

3. FunSuite example import org.scalatest.FunSuite class SetSuite extends FunSuite { test("An empty Set should have size 0") { assert(Set.empty.size == 0) } test("head of empty Set should produce NoSuchElementException") { intercept[NoSuchElementException] { Set.empty.head } } } Source: http://www.scalatest.org/user_guide/selecting_a_style

4. Three main methods These methods, along with any arbitrary Scala code, should go within test( Descriptive_string ) {…} Unfortunately, the syntax for each is different assert( Boolean_condition ) assert( Boolean_condition, clue ) The clue is a String used to provide additional information about the failure assertResult( expected_value ) { compute_actual_value } assertResult( expected_value, clue ) { compute_actual_value } intercept[ name_of_exception ] { code that should throw the exception } withClue( clue ) { intercept[ name_of_exception ] { code that should throw the exception } }

5. Don’t put too much in one test Here’s an example test: test("Testing Code.okToAdd") { val code = new Code assert(code.okToAdd('X', 'P')) code.add('X', 'P') assert(code.okToAdd('X', 'P')) assert(code.okToAdd('A', 'B')) assert(! code.okToAdd('X', 'B')) assert(! code.okToAdd('Y', 'P')) assert(! code.okToAdd('A', 'A')) } If any assertion fails, the rest of this test won’t be executed Other tests will still be executed

6. before and after Like JUnit, Scalatest has methods that are automatically called before each test (to make sure each test starts in a known state) and after each test (to clean up afterward) before { code } after { code } As with JUnit, before is often used, after is seldom used

7. Programming support All major languages have significant support: IDEs, test frameworks, active user groups, etc. Because my primary concern in this course is concepts, discussion of this support has been explicitly omitted Scala has a few more concepts to cover, but most new concepts in Scala are borrowed from other languages My hope is that, in future, you will have opportunities to use Scala Therefore, I want you to use the Scala IDE and Scalatest

8. The Scala IDE The Scala IDE is a customized version of Eclipse Since Scala has had many fewer years of development than Java, some Eclipse features (for example, History) don’t yet work Other IDEs, such as IntelliJ IDEA, have some Scala support, but the Eclipse-based one is the “official” IDE

9. TDD, Test Driven Design/Development Everyone in here should be familiar with TDD If not, here’s a summary: Write a test for the basic functionality of the method you intend to write Write just enough of the method to pass the test Refactor (clean up code without changing what it does) If necessary, add features to the test Add just enough to the method to pass the test Refactor Repeat until done If, despite all the testing, an error is discovered later: Write (or extend) a test to display the erroneous behaviour Fix the error

10. Rules for all Scala programs in CIS 554 Methods should be of two types: Methods that do computation and no I/O Ideally, methods should be free of side effects If a method does have side effects, those should not affect the results of subsequent tests All methods of this type should be tested with Scalatest Methods that do I/O and no computation Minimal computation can be done for purposes of formatting output or putting input into a particular form There is no need to use Scalatest for methods that do I/O It can be done, but it’s outside the scope of this course

11. The End