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Lab 3: Testing

In this lab you will get familiar with different testing strategies and practice with writing good unit tests in Java and TypeScript.

Concepts

Structural testing vs Specification testing: Two distinct types of unit testing are specification-based (historically: black-box) testing and structural (white-box) testing. Specification testing is when you write high-level test cases against the specification of a program, without using (or testing) the specific underlying implementation of the program. In structural testing, your tests are instead tailored to the specific underlying implementation of the code you are testing.

Code coverage: Coverage is the amount of code that has been executed by the tests. There are several coverage metrics, but one common metric line coverage is simply the percentage of lines (or statements) that have been executed by your unit tests.

Deliverables

  • Write tests for LinkedIntQueue in TypeScript and ArrayIntQueue in Java and execute them from within the IDE.
  • Achieve 100% line coverage for ArrayIntQueue and show coverage results in the IDE or as HTML report.
  • Describe your experience with the tradeoffs between structural testing and specification testing to the TA. (no written answer needed)

Instructions

Setup

Fork and clone the repo from https://github.com/CMU-17-214/f23-rec03. The code is set up with JUnit and ts-jest. You can use your IDE to open the folder of each language and run the existing test with the command in the readme.txt. You can also see Appendix 1 for how to run tests in IDE.

Testing

Write additional tests for code we've provided and use a code coverage tool to measure the coverage of your unit tests.

TypeScript

For LinkedIntQueue you will need to use specification-based testing, because the source code for LinkedIntQueue is not provided. Your tests will be based on the specified functionality of the IntQueue interface rather than the code of the underlying LinkedIntQueue implementation.

  1. Open TypeScript folder with IDE. Read the comments for the IntQueue interface in queue.js file, and familiarize yourself with each method.
  2. Run queue.test.ts file(see readme.txt for instructions). Write more test cases to finish the specification testing for LinkedIntQueue. See Appendix 2 for notation.

Java

For ArrayIntQueue use structural testing. Specifically test underlying implementation of the ArrayIntQueue class, not just test against the IntQueue specification.

  1. Open Java folder with IDE. Run IntQueueTest class in the IDE (see readme.txt). Change the mQueue variable to ArrayIntQueue and run testing again. Use your IDE to see the line coverage result. See appendix 3 for coverage tooling.
  2. Try to find 2 bugs in ArrayIntQueue by running your test. Fix each bug that was found.
  3. Write more test cases to achieve 100% line coverage. Hint: you also need to write tests for ensureCapacity. It is fine if you don’t have time to finish it during the class.

Appendix 1: Test Integration in VSCode

The Java plugin and Jest (for Javascript) plugin in VSCode provide great test integration functionality. The testing side panel shows all the tests of the current project. You can also run all tests or a particular test here.

lab03_test_side_panel

After running the test cases, the plugin also shows the failed test cases. Also, you can direct to the failed assertions, and VSCode can show the concrete reasons for the failures.

lab03_test_example

Appendix 2: Test Directories For Java

By convention in Maven, test files are placed in a test folder with the path src/test/java. You may need to create this directory if it does not exist. In some IDEs you may need to indicate that this directory contains test files for the IDE to recognize and run the classes. In this directory create the same package structure as in src/main/java and place the test class in the same package as the class to be tested.

Appendix 3: Coverage Tools

###Java### In Java, we already set up the project to use Jacoco for collecting Coverage. If you run mvn test or mvn site to execute the tests, it will produce a report in target/site/jacoco/index.html. You can check the pom.xml file to see how we enabled this. Open with a browser to view the coverage report.

Your jacoco report should be similar to this when viewed in the browser. lab03_jacoco_report

In IntelliJ you can run tests with Coverage directly from within your IDE: Right click on test class and select Run '$classname' with Coverage; there should be a panel that pops up the right side of the screen showing class coverage.

###TypeScript### For TypeScript, Jest can report coverage out of the box when run with the --collect-coverage option (enabled by default for npm test). It will print coverage summaries on the command line and also create an HTML report in the coverage directory.