This article brainstorms how design choices for better code testability fits into the big picture of providing a continuous stream of business value to the customer. Exploring the possible software design options even before the coding starts enables decoupling and dependency injection which makes the software all the more robust and flexible to absorb future changes in the customer requirements.
What is a unit? A unit is the smallest testable part of an application. Unit tests are written from the specification (FSD/TDD) based on how the product would be used by the end customer. It should be tested in isolation without any dependency. All the dependencies should be mocked up using stubs so that the unit tests are simple and fast. These tests are supposed to focus only on a specific action without any coding for the dependencies.
For example, the coder develops a method called validate_zip_code. When I enter zip code as 00000 it should return false. This is a unit test. As per the requirement spec, on the shipping form if the customer enters invalid zip code he should be re-directed to the help page that explains what is a zip code. Imagine that this help page is yet to be developed by a different team called consumer team. Testing both the zip code field and the display of help page is not unit testing but functional/integration testing. This dependency on the help page display needs to be separated from the validation of zip code. This separation is called dependency injection and it decouples the code making it more robust. The dependencies could be mocked using tools like mockito or easymock. Thus the coder needs to create a mockup or a simulator to substitute for the dependency.
Why dependency injection can ease unit tests? With dependency injection writing unit tests becomes easy and the execution of unit tests becomes simple and fast. This is because the coders are not required to write test code for dependencies as well. Writing code for dependencies makes unit tests complicated and it is also unnecessary since we are not going to do any functional testing with it.
Advantages of Dependency Injection:
1. Unit testing before coding adopts Test Driven Development. The coders can brainstorm the possible execution paths and corner cases that he had never thought of before. This results in a higher quality code
2. Code with lots of dependencies violates the Law of Demeter or the Hollywood principle. With dependency injection the code becomes loosely coupled
3. Determines if the code is fit for testing and increases the testability of the code
When there are a set of activities, which of these must be finished completely before we continue the process?
Fraud check and confirmation of funding source/shipping address should be done before payment is processed.
“When developing our test strategy, we must minimize the impact caused by changes in the applications we are testing, and changes in the tools we use to test them.” –Carl J. Nagle
This article evaluates the effectiveness of testing approaches and sheds light on the areas we need to concentrate on while testing. In essence 20% of the test cases should account for 80% of the ROI. For this, the testers need to question the logic behind the test case development by asking: 1) What is the probability of the occurence of bugs in this area? 2) Do I really need to automate this test? 3) What is the impact of GUI changes on the test case? The testers who are short-sighted tend to focus only on the testing milestones like pass rate/deadlines and fail to achieve the long term goals of testing like maintainability, robustness and coverage.
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In this testing approach we try to simulate a customer completing some task involving multiple features and system interactions. This is the least effective test automation approach
1. Exposes Behavioral issues
1. Maintenance nightmare: Whenever the GUI changes the tester needs to revise the test case. GUI test cases are tied to the very trivial details of the UI that almost any change in the GUI can cause the test cases to fail. Thus, maintenance becomes tedious. Considering the time to fix it we could rather re-create the test case from scratch
2. Last minute design changes can cause havoc to the automation team
3. Longer test case execution time
4. Does not find much bugs
While developing the test strategy we must minimize the impact of UI changes on the test cases. I would recommend executing GUI test cases later in the lifecycle when the UI is stable and after all the critical fuctional bugs are exposed by the approach “Component based” testing explained below.
In this testing approach we directly hit/communicate with the component to test the application. A component is an integrated aggregate of one or more units. We parameterize the properties and pass it as the input data to the API. The corresponding methods are triggered on the data and it tests the underlying business logic/functionality of the application.
1. Maintainable: As opposed to End-to-End testing this is not dependent on UI changes and hence reduces the automation efforts.
2. Faster test case execution time and hence reduces the Mean Time To Test (MTTT)
3. Finds many bugs early on in the lifecycle. Exposes functional issues