CS159. Nathan Sprague. September 30, 2015

Transcription

1 CS159 Nathan Sprague September 30, 2015

2 Testing Happens at Multiple Levels Unit Testing - Test individual classes in isolation. Focus is on making sure that each method works according to specification. Integration Testing - Test the interaction between classes. Validation Testing - Test the entire system in context.

3 Different Perspectives Black-box testing Develop tests on the basis of class specifications and documentation. White-box testing Develop tests on the basis of implementation. Aim for high code coverage.

4 JUnit - Sample Test Class 1 import static org. junit. Assert.*; 2 3 import org. junit. Before ; 4 import org. junit. Test ; 5 6 public class PointTest 7 { 8 private Point testpoint ; 9 11 public void setup () throws Exception 12 { 13 testpoint = new Point (5.0, 6.0); 14 } public void testtostring () 18 { 19 assertequals (" (5.0, 6.0) ", testpoint. tostring ()); 20 } 21 }

5 Testing Example 1 public class Estimator 2 { 3 public static int totalcost ( boolean fast, boolean good ) 4 { 5 int total = 0; 6 if ( fast ) 7 { 8 total += 5; 9 } 10 if ( good ) 11 { 12 total += 10; 13 } 14 return total ; 15 } 16 }

6 Method Coverage 100% method coverage: testing code calls each method at least once. 2 public void totalcosttestslowbad () { 3 assertequals (0, Estimator. totalcost ( false, false )); 4 } Done! Reassuring?

7 Method Coverage 100% method coverage: testing code calls each method at least once. 2 public void totalcosttestslowbad () { 3 assertequals (0, Estimator. totalcost ( false, false )); 4 } Done! Reassuring? No, but better than NOT having 100% method coverage.

8 Style Suggestion JUnit assertion methods take an optional failure message as the first parameter: 2 public void totalcosttestslowbad () { 3 assertequals (" Estimate should have been 0.", 4 0, Estimator. totalcost ( false, false )); 5 } My suggestion: don t provide a message Instead: One assertion per test method Very descripted method names

9 Statement Coverage 100% statement coverage: testing executes every statement. 2 public void totalcosttestfastgood () { 3 assertequals (15, Estimator. totalcost ( true, true )); 4 } Better? Happy?

10 Branch Coverage 100% branch coverage: all outcomes are executed for each branch. 2 public void totalcosttestslowbad () { 3 assertequals (0, Estimator. totalcost ( false, false )); 4 } 5 7 public void totalcosttestfastgood () { 8 assertequals (15, Estimator. totalcost ( true, true )); 9 } Good enough?

11 Path Coverage 100% path coverage: testing exercises every possible path through the code. 2 public void totalcosttestslowbad () { 3 assertequals (0, Estimator. totalcost ( false, false )); 4 } 6 public void totalcosttestfastgood () { 7 assertequals (15, Estimator. totalcost ( true, true )); 8 } 10 public void totalcosttestslowgood () { 11 assertequals (10, Estimator. totalcost ( false, true )); 12 } 14 public void totalcosttestfastbad () { 15 assertequals (5, Estimator. totalcost ( true, false )); 16 }

12 Path Coverage 100% path coverage is typically considered an impractical target. It is a useful idea to have in mind while developing tests.

13 Test-Driven Development Write tests first. Helps clarify specifications. Helps avoid mistakes in development.

14 Developing Test Cases To guarantee correctness, test every possible sequence of method calls, with every possible input value. Usually not possible. Instead, look for boundary conditions Points where the behavior of the code should change Test at the boundaries and on either side. Also test erroneous inputs We ll work through an example in a few minutes...

15 Regression Testing Testing is not a one-time process. Ideally, unit tests are maintained along with the code. This makes it safer to change the code: All tests can be run after every change.

16 Brainstorm Some Tests... 1 /** 2 * Returns the point with the smallest x- coordinate 3 * among all points in the array. In the case of a tie, 4 * the point that appears first will be returned. 5 * 6 points - An array of point objects 7 - The leftmost point 8 - IllegalArgumentException If the length 9 * of the array is NullPointerException If the array, or any 11 * entries in the array, 12 * are null. 13 */ public static Point findleftmost ( Point [] points ) 16 throws IllegalArgumentException, 17 NullPointerException