Tips for writing Unit Test Cases – Continued

Hi all,

Hope you are doing well. I wish to add some thoughts on writing better unit tests.

Many a times we need to pass parameters to the Unit Test cases that we write. This can be accomplished using TestCase attribute, such as this.

But the TestCase attribute requires a constant argument. What if we need to assemble a complex Object and pass to the unit test case?

1. Calling a helper method from the TestCase parameter to assemble an object? - No (As only constants can be passed as Positional Parameters to attributes)

Work Around:

This can be achieved by exploiting the power of factory pattern.

Consider the following test case, where we need to pass different employee instances (may be even Employee is an abstract class and has two Childs, Manager and Labour. )

The test case for both the Concrete classes can be written in one neat way as above.

The Factory class which serves as the input container is as follows .

This approach avoids the coupling between unit tests and the input sets , and more over reduces the redundant code by a large margin.

I shall blog about the Combinatorial attribute in the next post.

Thanks,

Vijay

How to expose internal members of a class to Unit Test cases

Going by the convention of design patterns, it is always safe to have the members of a class as private or internal, In order to clearly abstract away the implementation details from the external world. The Classical example of this being Domain Model (Repository Pattern) where all the methods including constructors are made protected internal.

Example:

But there is a bottle neck in doing this. For maintainability purposes SUT (System under Test) (the internal method GetTime()in our case) and Unit test cases for testing the GetTime()) are placed in separate assemblies . Hence from the Unit Test cases, it is not possible to instantiate Class2 and test the GetTime() method .

This can be overcome by the InternalsVisibleTo attribute located in System.Runtime.CompilerServices namespace. The attribute takes the friend assembly’s name (the assembly to which the SUT has to be exposed) as an argument. The attribute when placed upon the namespace of the current assembly, is safely exposed to the target assembly (friend assembly).

Example:

This workaround is similar to the concept of Friend functions in C++, which is the only way by which a Class can access the private members of another Class(of course sparing pointers).

Everything about AJAX

I was trying to read some articles relating to AJAX, and found this to be extremely useful.

http://ajaxtraining.blogspot.com/

Accessing live cricket score from C# Win Forms Application - Using Screen Scrapping technique.

Quite often during the crucial stages of a cricket match, we might want to refresh the browser frequently, in order to get the latest score. And more importantly we need to stay in the browser window.

This can be done programmatically, through the following steps.

1. Launch an embedded web browser in a C# win forms application.

2. Supply the URL of the page which publishes the latest cricket score.

3. Capture the entire HTMLDOM of that page.

4. Identify the HTML element which displays the score (that is changing) and save the index of that HTML element (the index is unique for all the HTML elements).

5. Load the entire HTMLDOM once again and Get the element by index (already saved).

6. Querying for the text at that element gives you the latest score.

7. Run the steps 5, 6 on a timer (say 7 seconds to keep refreshing the page.)

Note: The HTML markup of the page should not change while scrapping.

Code Snippets:

Steps -1, 2

Steps -3, 4

 

Steps 5,6,7

This technique can be ideally used to ‘scrape’ weather updates, Stock rates etc, which keeps changing frequently.

DevWeek - Code/Presentation

http://www.devweek.com/code/

Accessing Twitter API through C# code

I wanted to share the C# code which i used to access , the Twitter API programmatically .

The Workflow.

1. Twitter exposes almost all its data underneath, through its RESTFul Services

2. The Client using this code  can be a Webclient(asp.net , asp.net mvc etc ) or a Desktop client (Winforms , Console Application etc.)

3. The data being returned from those services are in XML or JSON format.

Code Snippet

Unit Testing in .NET - Best Practices

Think Agile - Practice TDD

View more presentations from vijay sylvester.