Assignment 2: Estimating Testing Effectiveness

Due Friday, October 19

Goals for This Assignment

By the time you have completed this work, you should be able to:

Measure code coverage
Perform mutation testing
Write tests that maximize code coverage and killed mutants

This assignment may be completed in groups.

Step-by-Step Instructions

Step 1: Download and Unzip Needed Code

Download the code here, and unzip it. This is the same code that we have been working with in class.

Step 2: Install Maven

Install Maven. If you're using Linux, binary packages are usually available through your distribution's package manager. If you're using Mac OSX, binary packages are available via Homebrew.

Step 3: Compile Code with Maven

Code is already provided in src/main/java/trees/TreeOperations.java. This code should compile as-is. You should be able to compile your code with the following command:

mvn compile

If your code doesn't compile, it may be because your version of Java is improperly set in the provided pom.xml. To check this, run the following:

java -version

This will give you output like the following:

openjdk version "1.8.0_171"
OpenJDK Runtime Environment (build 1.8.0_171-b10)
OpenJDK 64-Bit Server VM (build 25.171-b10, mixed mode)

The version number in the first line should match up with the version number in the maven.compiler.source and maven.compiler.target lines of pom.xml. In this case, the version number of 1.10 is incorrectly set in pom.xml, and should instead be set to 1.8.

Step 4: Write Implementation

As with the in-class exercise, you should write the following three methods in src/main/java/trees/TreeOperations.java:

A breadth-first search over a tree, returning the items in the tree. Different method signatures are possible for this. If you're stuck, you can use the following signature:
```
          public static <A> ArrayList<A> bfs(final Node<A> root)
        
```
A pre-order traversal over a tree, returning the items in the tree. Different method signatures are again possible; you can use the following if you're stuck:
```
          public static <A> ArrayList<A> preorder(final Node<A> root)
        
```
A calculation of the maximum depth of a given tree. Different method signatures are again possible; you can use the following if you're stuck:
```
          public static <A> int maxDepth(final Node<A> root)
        
```

You may write helper methods if you wish.

Step 5: Write Tests

Write JUnit tests for your methods in src/test/java/trees/TreeOperationsTest.java. Try to write tests that you think will cover all parts of your code. You can run your tests with the following command:

mvn test

All of the tests you write should pass.

Step 6: Measure Coverage and Possibly Write More Tests

You can measure the coverage of your tests with the following commands:

mvn test
mvn jacoco:report

These comments will compute the coverage information. You can then view the results by opening target/site/jacoco/index.html. The results have links that will allow you to explore your code, and see line and branch coverage information.

For the purposes of this assignment, you should have at least 90% line and branch coverage over your entire implementation (line and branch coverage are separate measurements). If you have less than 90% coverage, you should return to step 5 and incrementally improve your coverage. The only exception is if you can explain why the coverage is below 90%, and exactly why it cannot be improved.

Step 7: Perform Mutation Testing and Possibly Write More Tests

You can perform mutation testing (also known as mutation analysis) with the following commands:

mvn test
mvn org.pitest:pitest-maven:mutationCoverage

These commands will perform mutation testing. You can view the results by opening target/site/pit-reports/<<representation of most recent date and time>>/index.html. This will show you the mutants that were created, along with which were killed and which survived.

For the purposes of this assignment, you should kill at least 90% of the mutants. If you have less than 90% killed mutants, revisit step 5 and improve this ratio. The only exception is if you can explain why this ratio is below 90%, and exactly why it cannot be improved.

Step 8: Submit Everything

Zip up everything in your coverage_mutation_template directory, including the target directory. Be sure your target directory holds up-to-date coverage and mutation testing results. Name your zipfile coverage_mutation_solution, and submit it on Canvas. In the comments for the submission, list everyone you worked with, if applicable. If you had less than 90% coverage or mutants killed, similarly explain in the submission comments on Canvas.