Test Abstraction

I’m staring at a single CppUnit test function spanning hundreds of source lines. The test developer inserted visual indicators to help me pick out the eight test cases it covers:

//++++++++++++++++++++++++++++++++++++++++++++++++++

Each of these cases is brief: four to eight lines of data setup, followed by a execution statement enclosed in a CPPUNIT_ASSERT. Of course they could be broken up into eight separate test functions, but otherwise they are reasonable.

Prior to the eight tests there are two hundred lines of setup code. Most of the initialization sets data to reasonable default values so that the application code won’t crash and burn while being exercised.

I don’t know enough about the test to judge it in terms of its appropriateness as a “unit” test. It seems more integration test than anything. But perhaps all I would need to do is cleverly divorce the target function from all of those data setup dependencies, and break it up into eight separate test functions.

The aggregation of tests is typical, and no doubt comes from a compulsion to not waste all those 200 lines of work! The bigger problem I have is the function’s lack of abstraction. Uncle Bob always says, “abstraction is elimination of the irrelevant and amplification of the essential.” When it comes down to understanding tests, it is usually a matter of how good a job the developer was at abstracting intent. Two hundreds of lines of detailed setup does not exhibit abstraction!

For a given unit test, I always want to know why a given assertion should hold true, based on the setup context. The lengthy object construction and initialization should be encapsulated in another method, perhaps createDefaultMarket(). Relevant pieces of data can be layered atop the Market object: applyGroupDiscountRate(0.10), applyRestrictionCode(), etc. Not only does it help explain the data differences and correlate the setup with the result, it makes it easier to read the test, and easier to write new tests (reuse!).

I often get blank stares when I ask developers to make their tests more readable. Would they respond better to requests to improve their use of abstraction?

Atom