Binghamton University. CS-140 Fall Unit Testing

Transcription

1 Unit Testing 1

2 Test Early, Test Often 2

3 Informal Unit Testing public static void main(string[] args) { Rectangle rect = new Rectangle ( new Point(20,30), 20,40 ); System.out.println("Created " + rect); rect.grow(1.25); System.out.println("Grown by 25%, thats: " + rect); Point pq = new Point(40,65); System.out.println("This rectangle " + ( rect.contains(pq)? "does" : "does not" ) + " contain point " + pq); } 3

4 Informal Results Only works when you remember the right answer Does not isolate problems Works well right after you write the code, but not so well a couple of months later No way to quantify how well the code works 4

5 Alternative : JUnit Testing Supported by Eclipse Formal method to test each method Reproducible tests even when run by somebody else Quantified results Tests easy to extend 5

6 Create a Junit Test Class In Eclipse, Select package, right click New (or click on the Select Junit Test Case Fill in Name and Class Under Test options icon) Select method stubs if desired Use setup and teardown for code to be run before and after each test Use setupbeforeclass and teardownafterclass to do a one-time setup and one-time tear-down Click on Next 6

7 Junit Test Case Wizard, Screen 1 7

8 Select Methods to Test 8

9 Eclipse creates a Unit Test Class 9

10 Unit Test Class Organization Often no fields, no constructor Annotations on methods to define what they This is a separate test This method is invoked before each This method is invoked after each This method is invoked before all test This method is invoked after all test methods Eclipse Wizard already provides these See for more 10

11 What s in Method? There are several static methods that can be invoked, all documented in ssertions.html If nothing is invoked, the test passes If fail is invoked, the test fails, for the reason specified 11

12 Example Tests 12

13 Using assertequals assertequals(expected,actual) Various different types are allowed for expected and actual byte, char, double,float,short,int,long,object For float and long, third argument, delta for comparison Final optional argument: string explaining more about what is wrong Note there are also asserttrue and assertfalse assertnotequals, assertnull, assertsame assertarrayequals 13

14 Example assertequals 14

15 Example Passing Tests 15

16 Testing Exceptions Use assertthrows First argument expected type of exception to be generated Second argument Executable to run the method Either a lambda expresson: ()->XmpFunc.sequence(x,y,z) Or a method reference: XmpFunc::sequence(x,y,z) Returns the exception thrown Enables further checking May be ignored if desired 16

17 Testing Performance asserttimeout First argument Duration Second argument executable Fails if executable takes longer than duration Does not stop until executable finishes Use asserttimeoutpreemptive if you want to stop before executable finishes 17

18 Unit Test Philosophy Write unit tests BEFORE you write your code Fix all bugs found As time goes on (e.g. system testing, user testing, etc.) more bugs will be uncovered add these to your unit tests as you find and fix these bugs That will ensure that your code permanently fixes all bugs you have seen 18