1. BlueJ Tester
By Pepper

2. What is Tester?
Tester makes it easy for you to run test cases through your method that returns a value.
You code the test cases
You run the one test
It reports all failures with expected vs actual

3. Why use tester Unit testing Regression testing Alternatives:
When you can count on a function working, it is makes debugging the main program easier
It is easier to fix a smaller amount of code
Regression testing
Guard against changes breaking code
Alternatives:
Call method frequently typing in values (if value can be entered through BlueJ interface)
Code tests in main method (and verify results and print notices for failure)

4. Test a Static Method’s Return
Right click on class box – create test class
Double click green unit test box to edit
Remove extends junit.framework.TestCase
import tester.*;
public class MyPgmTest {

5. Test a Static Method’s Return
Fill in testSomething method
3 parts:
Command : t.checkExpect
Method call: MyPgm.addIt(3)
Method return: 6
t.checkExpect( MyPgm.addIt(3) , 6 );
Make many tests
t.checkExpect(MyPgm.addIt(3),6);
t.checkExpect(MyPgm.addIt(5),5);

6. Complete Test Program
import tester.*; public class MyPgmTest { public static void testEverything () { Tester.run (new MyPgmTest()); } public void testSomething (Tester t) { t.checkExpect (MyPgm.addIt(2),5); t.checkExpect (MyPgm.addIt(2),4);

7. Run Tests Right click on test block and compile
Right click on test block and run testEverything()
See the results of each test in the terminal window
Note: You can add other methods if you like

8. Testing Double Value Matching
How to represent 1.1?
The problem: between 1/8 and 1/16
× 2-4

9. More information for doubles
More on float and doubles:
Explains how values are held
Explains rounding rules
No need to learn how, just know to expect it slightly off with tolerance .001

10. Inexact - Checking Doubles
Check doubles by only insisting on .001 tolerance.
4 parts:
Command : t.checkInexact
Method call: MyPgm.addIt(3)
Method return: 6
Tolerance: .001
t.checkInexact( MyPgm.addIt(3) , 6, .001 );

11. Summary
Use tester for unit and regression tests of methods with return values
Doubles (and float) are inexact storage of fractions, so expect tolerance needed
How to set up tests for exact and inexact
How to run tests
How to see results