Creating Tests for LCD Numbers Kata by Mocking Collaborators
For other languages see
Requirements (copied from Ruby Quiz)
toLcd creates an LCD string representation of an integer value using a
4x7 grid of space each, using minus and pipe characters for each digit.
Each digit is shown below:
-- -- -- -- -- -- -- -- | | | | || || | || || | | | | | || || | || || | -- -- -- -- -- -- -- | | || | | || | || | | | | || | | || | || | | -- -- -- -- -- -- --
The bar size should be adjustable. The default value is 2 - as shown above. Read more about it at RubyQuiz.
Description of Existing Solution
To make things easier for you, here is the description of the solution used in the code:
toLcd is the entry point. The given number is split into digits by
digitsOf (which uses the Decimal System in our case). Then the initial
pattersOf by copying the template
Lines. Then the (LCD) digits are scaled
scaleDigits according to the
Scaling value. The actual scaling is done inside
scalingRepeat function by repeating certain rows and columns of the template.
Finally the list of digits is combined to a single String by
There is a script
index.js to see the LCD Numbers working. There you can see how all the
functions are assembled and collaborators are combined with each other.
You can run it with
node src/index.js <number, e.g. 123> <size, e.g. 2>
Creating Unit Tests
Create unit tests for all classes and functions. Make sure all units are tested in isolation.
The point of this exercise is to go extreme to practise using test doubles.
Create test doubles for everything! Create dummy objects for all used values
and stub all collaborators, even the simple values
- Start testing the simple units like
Digit. These classes have a single (interesting) method with a single collaborator.
- Work on
renderDigits. Both have more logic, but still only a single collaborator.
- Things are getting more complicated with
- Finally go for
toLcdwhich has three collaborators.
There are sample LCD outputs in the
test/resources folder to be used in tests.
size_3 folders contain each digit in original size and
scaled twice and three times.
Check your Coverage
To measure your progress you should use code coverage tools:
Enforcing all calls to other functions in a test is not recommended in real unit tests because this leads to bad tests which are bound to the implementation. These over specified tests make it impossible to change the code under test without breaking. We want to be able to change the code without breaking the test as long as the required functionality is not changed. This exercise is for practising test doubles.
This work is licensed under a New BSD License, see
license txt in repository.