TDD + ESpec. Test-Driven Development. A test specifies a class interface. Test First Square Root of 10

Transcription

1 Test-Driven Development TDD + ESpec TDD Test Driven Design» Change in software development paradigm» Write tests before code!!! > Step One: write a little test > Step Two: make it pass > Step Three: refactor» Tests are also a type of specification > Contracts specify obligations and benefits for clients and suppliers > Tests specify class behaviour Example: let s write some code to find square roots of DOUBLE numbers. Test First Square Root of 10 A test specifies a class interface Result := m.sqrt(10) = Result := m.sqrt(10) = class MATH feature sqrt (x: DOUBLE): DOUBLE

2 sqrt (x:double): DOUBLE is Implementation A better test what is the precision d: DOUBLE Result := d := 10 - m.sqrt (10)*m.sqrt (10) Result := d.abs <= m.epsilon A test specifies the class interface Tests vs. Contracts d: DOUBLE d := m.sqrt (10)*m.sqrt (10) - 10 Result := d.abs <= m.epsilon class MATH feature epsilon: DOUBLE sqrt (x: DOUBLE): DOUBLE Test» Result := (m.sqrt (10)*m.sqrt (10) - 10).abs <= m.epsilon» This only specifies the value for one value: 10 Contract sqrt (x: DOUBLE): DOUBLE is -- implementation goes here ensure (Result * Result x).abs <= epsilon Might want to add a constructor to set an initial value for epsilon

3 Tests vs. Contracts Test» Result := (m.sqrt (10)*m.sqrt (10) - 10).abs <= m.epsilon Contract» (Result * Result x).abs <= epsilon The contract is a more general specification of the correct behaviour than the test The unit test can be used to exercise and verify the contract.» i.e. the test amplifies the contract Write Code with contracts class MATH feature epsilon: DOUBLE -- calculation precision -- e.g..001 means 3 decimal places sqrt (x: DOUBLE): DOUBLE is -- implementation goes here ensure result_accurate: (Result * Result x).abs <= epsilon epsilon_unchanged: epsilon = old epsilon What about a negative argument x? test_sqrt_negative5: BOOLEAN is class MATH feature Write Code with contracts epsilon: DOUBLE -- calculation precision -- e.g..001 means 3 decimal places Result := (m.sqrt(-5)*m.sqrt(-5) (-5)).abs <= m.ε sqrt (x: DOUBLE): DOUBLE is require argument_non_negative: x >= 0 -- implementation goes here The problem is that any number multiplied by itself is always positive there is no real number that can be returned The specification will never be satisfied no matter the implementation ensure result_accurate: (Result * Result x).abs <= epsilon epsilon_unchanged: epsilon = old epsilon invariant minimal_precision: 0 <= epsilon and epsilon <=.001

4 Violation test case What is espec? test_negative_no is -- in `sqrt(x)' argument `x' must be non-negative value: DOUBLE value := m.sqrt (-2) print ("Should not get here") To make the test case pass, the require clause should throw an exception A collection of classes that help organize the test cases for a program A user adds test cases to the appropriate structure The espec process runs the test cases A report is made in the espec winw If you launch the test cases from within estudio, a report is made in an html file for every class and one that combines all classes. You read the reports with a browser.» This is painful for precondition tests, as you must continue the execution after each precondition violation Installing espec Example use of espec part 1 All tests in one class espec is automatically included in any project you create at Prism To work at home, go to the following web page and follow the instructions Be sure to install Eiffel 5.7 first The Online Tutorial contains a video you can wnload and may be able to run in your browser The Help button is also useful. class ROOT_CLASS inherit ES_TEST creation make feature make is add_boolean_case (agent bool1) add_violation_case (agent viol1) run_espec

5 Example use of espec part 2 Feature -- Test class creation Have one TEST_CLASS for every class you want to test class TEST_CLASS inherit ES_TEST creation make feature -- Test class creation See slide Feature -- Test class creation make is -- Defines the test cases to use add_boolean_case (agent test_junk) add_violation_case (agent test_precondition) feature -- Test cases See slide Feature -- Test cases -- TEST_CLASS Feature -- Test cases creation test_junk : BOOLEAN is comment("test_junk") Result := true -- Try with false test_precondition is array : ARRAY[STRING] comment("test_precondition") create array.make(5,1) -- Try with make(1,5) Putting many test classes together Have one ROOT_TEST for the system class ROOT_TEST Note different inherit ES_SUITE inherited class creation make feature make is One for each class to test add_test(create {TEST_CLASS_1}.make) add_test(create {TEST_CLASS_2}.make) run_espec

6 View test results Run espec» In Winws run as a separate program» In Linux run with & before using estudio or run in a separate winw Use the browse button to select the executable system which is deep wn in the EIFGENs directory for your compiled system» your system --> EIFGENs --> W_code --> systemname > The systemname the one in the ACE file. > Select the systemname with no extensions