error - a mistake made by a human (in a software development activity)
defect (or fault ) - the result of introducing an error into a software artifact (SRS, SDS, code, etc.)
failure - a departure from the required behavior for a system
A vicious cycle – the more pressure a you (Developer) feel, the fewer tests you writes. The fewer tests you write, the less productive you are and the less stable your code becomes. The less productive and accurate you are, the more pressure you feel. The Problem
The required functionality for a particular service (getVersionsForProductId) is the ability to get a list of all versions for a given product id. If there’s no product for that id, then an exception is thrown. If there’s no versions for a valid product id, then an empty list is returned.
The Tests That Are Needed
Starting from the easiest to the hardest:
If there’s no product for that id, then an exception is thrown (pre-condition)
If there’s no versions for a valid product id, then an empty list is returned (post-condition)
If there are versions for a product id, then a non-empty list of all the versions is returned (post-condition)
Additionally the following information may also be captured: a) Unit Name and Version Being tested b) Tested By c) Date d) Test Iteration (One or more iterations of unit testing may be performed)
Comment if any Pass / Fail What actually happens. This column can be omitted when defect recording tool is used. What should happen? Input Data How to Test What to Test ID which can be referred to in other docs like “TM” “Root Cause Analysis of defects etc Remarks Pass / Fail Actual Result Expected Result Input Data TC Procedure Test Case Purpose Test Case
Documentation: Early on document all the Test Cases needed to test your code. Document the Test Cases, actual Results when executing the Test Cases, Response Time of the code for each test case.
Important advantages if the test cases and the actual execution of test cases are well documented.
Documenting Test Cases prevents oversight .
Documentation clearly indicates the quality of test cases .
If the code needs to be retested we can be sure that we did not miss anything.
It provides a level of transparency of what was really tested during unit testing. This is one of the most important aspects.
It helps in knowledge transfer in case of employee attrition.
Sometimes Unit Test Cases can be used to develop test cases for other levels of testing
What should be tested when Unit Testing It could be a screen or a component or a web service
Test Cases to verify all the screen elements that need to appear on the screens.
Test cases to verify the spelling/font/size of all the “labels” or text that appears on the screen.
Test Cases such that every line of code in the unit is tested at least once in a test cycle.
Test Cases such that every condition in case of “conditional statements” is tested once.
Test Cases to test the minimum/maximum range of data that can be entered.
Test Cases to verify how various errors are handled .
Test Cases to verify if all the validations are being performed
Never write a test that succeeds the 1 st time Start with null case, or something that doesn’t work Try something trivial to make the test work Loose coupling & testability go hand in hand Use mock Objects Write the test first Charles' Six Rules of Unit Testing
A normal unit test should test for the functional requirements . But if the non-functional requirement performance or speeds depend on the size of the data, you should test that too.
Perhaps absolute performance, or
Perhaps how performance changes as input grows.
Perhaps separate test suite in JUnit
Example: a spam filter that tests against “naughty” or black-listed mail servers. Test your code with different lists sizes. Typically a small list for build testing, but maybe also with a longer list e.g. once a day.
Benefits of Unit Testing It provides a strict, written contract that the piece of code must satisfy. It find problems early in the development cycle. It allows the programmer to refactor code at a later date , and make sure the module still works correctly (i.e. regression testing). It may reduce uncertainty in the units themselves and can be used in a bottom-up testing style approach. It provides a sort of living documentation of the system . Developers looking to learn what functionality is provided by a unit and how to use it. By testing the parts of a program first and then testing the sum of its parts, integration testing becomes much easier.
Naming standards for unit tests BAD_DATA or EMPTY_ARRAY or NON_INITIALIZED_PERSON Variable names should express the expected input and state Public void Sum_NegativeNumAs1stParam_ExcepThrown() Test name should include name of tested method or class. [MethodName_StateUnderTest_ExpectedBehavior] testCalculator() Test Name should only begin with Test if it is required by the testing framework or if it eases development and maintenance of the unit tests in some way. Public void SumNegativeNumber2() Test name should be presented as a statement or fact of life that expresses workflows and outputs Public int Sum(params int values), Public int Sum_NumberIsIgnored() Test name should include the expected input or state and the expected result for that input or state Public void Sum_simpleValues_Calculated () Test name should express a specific requirement. The basic naming of a test comprises of three main parts [MethodName_StateUnderTest_ExpectedBehavior]
Naming standards for unit tests- Cont…… : The [Category] attribute when applied to a method associates the Test within a user-defined category. Category Tests with the [Ignore] attribute are skipped over when the Tests are run . Ignore: Tests with the [Explicit] attribute won't run unless you manually run them . Explicit: Similar to finalizers Fixture TearDown Similar to constructors. Fixture Setup a method with the [TearDown] attribute is called at the end of every test within a fixture. TearDown Test Fixtures can designate a special piece of code to run before every Test within that Fixture. That method is decorated with the [Setup] attribute. SetUP Methods within the Fixture that are decorated with the [Test] attribute and contain code that validates the functionality of our target . Test Test Suites are an older style of organizing tests. They're specialized fixtures that programmatically define which Fixtures or Tests to run. Suite Synonymous with " TestFixture ", a fixture is a class that contains a set of related tests. Fixture to refer to the piece of functionality that is testing. Target / Subject
Naming standards for unit tests- Cont…… you should only write the methods that you need today. Adding methods for future purposes only adds visual noise for maintenance purposes AVOID: Empty Setup methods (You can always go back) CONSIDER: Splitting Test Libraries into Multiple Assemblies Suites represent significant developer overhead and maintenance. Categories offer a unique advantage in the UI and at the command-line that allows you to specify which categories should be included or excluded from execution. CONSIDER: Using Categories instead of Suites or Specialized Tests For example, you could execute only "Stateful" tests against an environment to validate a database deployment. In scenarios where you are testing sets of common classes or when tests share a great deal of duplication, consider creating a base TestFixture that your Fixtures can inherit. CONSIDER: Deriving common Fixtures from a base Fixture If you have a requirement where you want to test in production or verify at the client's side, you can accomplish this simply by bundling the test library with your release. CONSIDER: Separating your Tests from your Production Code.
Naming standards for unit tests- Cont…… If your application has features that differ slightly for application roles, it's likely that your test names will overlap. CONSIDER: Using prefixes for Different Scenarios Some have adopted a For<Scenario> syntax (CanGetPreferencesForAnonymousUser). Other have adopted an underscore prefix _<Scenario> (AnonymousUser_CanGetPreferences). Since Exceptions are typically thrown when your application is a performing something it wasn't designed to do, prefix "Cannot" to tests that are decorated with the [ExpectedException] attribute. CONSIDER: Use "Cannot" Prefix for Expected Exceptions Examples: CannotAcceptNullArguments , CannotRetrieveInvalidRecord . Most tests require special knowledge about the functionality your testing, so a little documentation to explain what the test is doing is helpful. DO: Document your Tests A few comments here and there are often just the right amount to help the next person understand what you need to test and how your test approaches demonstrates that functionality. The test name should match a specific unit of functionality for the target type being tested. Some key questions you may want to ask yourself: "what is the responsibility of this class?" "What does this class need to do?" Think in terms of action words. DO: Name Tests after Functionality For example, a test with the name CanDetermineAuthenticatedState provides more direction about how authentication states are examined than Login .
Naming standards for unit tests- Cont…… Sometimes we create tests for bugs that are caught late in the development cycle, or tests to demonstrate requirements based on lengthy requirements documentation . As these are usually pretty important tests (especially for bugs that creep back in). AVOID: Unclear Test Names it's important to avoid giving them vague test names that represent a some external requirement like FixForBug133 or TestCase21 . PascalCase should suffice. Imagine all the time you save not holding down the shift key. AVOID: Using underscores as word-separators use_underscores_as_word_separators_for_readability, If you find that your tests are named after the methods within your classes, that's a code smell that you're testing your implementation instead of your functionality. AVOID: Naming Tests after Implementation If you changed your method name, would the test name still make sense? Tests that are marked with the Ignore attribute should include a reason for why this test has been disabled. AVOID: Ignore Attributes with no explanation
Naming standards for unit tests- Cont…… Finished with Unit Testing As Categories are sensitive to case and spelling, you might want to consider creating your own Category attributes by deriving from CategoryAttribute. CONSIDER: Defining Custom Category Attributes Using Categories is a powerful way to dynamically separate your tests at runtime, however their effectiveness is diminished when developers are unsure which Category to use. Categories DO: Limit the number of Categories
“ Unit Testing” is the most important one. Detecting and fixing bugs early on in the Software Lifecycle helps reduce costly fixes later on. The Above article explains how Unit Testing should be done and the important points that should be considered when doing Unit Testing.