I would like to ask about using Unit Testing in Web Development. The idea of Unit Testing is great but does it really bring value in the context of web application? Second part of my question is about TDD. If one creates an integration test before the actual code can this approach be called "Test Driven Development"?
1. Assumptions
By the definition Unit Test should test code on only one service layer. If a test tests code across multiple layers we have an integration test.
2. Argument
2.1 No Algorithms
There are not many algorithms in a Web Application. It's not like building a 3D Physics engine where every method does something challenging and hard to debug. Web application is mostly about integration and generating HTML.
The biggest challenges for a web application are: - clean code (universal problem for any software but not testable) - data consistency - integration (Programming Language, File System, Configuration Files, Web Server, Caching Systems, Database, Search Engine, External APIs - all those systems have to work together at a request)
If you want to build a Unit Test for every class in a web app you will be testing (in most cases): filling arrays, string concatenations and languages' native functions.
2.2 Cost
Just because a Web App is all about integration there are always multiple dependencies. You have to mock many different classes and writing even a small test might be actually a big job. What's even worse it's not only about test. Software needs to be testable. It means that one has to be able to inject dependencies in almost every class. It's not always possible to inject dependencies without creating additional layer between two classes (or systems). It complicates code and makes it more expensive to work with.
3. Integration Test
If web development is all about integ