如何测试数据检索模块？

Question

I am working on a project and have a data retrieval module written on python. All it does is build a query using string manipulations and then executes the query using another module (a connection module). I want to make unit tests properly. Does anyone have any recommendations on techniques? Is mocking a proper way to do so?

Answer 1

Your code consists of a computational part (building a query string) and an interactional part, where the actual communication with the data base is performed. If these two are combined, the code looks as follows:

def fetchData(self):
    query = ... some string building logic here
    results = ... database access using query

In code like this, just to check the string building logic in unit-testing, you would mock the data base access (to avoid the dependency on the data base in your unit-tests for various reasons). In the subsequent integration testing, you would then test the interaction of fetchData with the real data base.

An alternative approach is to extract the algorithmic part (the creation of the query string) into a separate method such that you can easily test this part independently.

def buildQuery(self):
    query = ... some string building logic here
    return query

def fetchData(self):
    query = self.buildQuery()
    results = ... database access using query

This makes your unit-testing simpler, because for the testing of buildQuery you don't need to do any mocking of the data base. Again, in integration testing you would then test the interaction of fetchData with the real data base.