Clone this repo.

git clone https://github.com/datamade/fix-a-bug.git && cd fix-a-bug

Install the requirements. (Feel free to use a virtual environment!)

pip install -r requirements.txt

Run the tests.

pytest -sv

The code in fix_me.py contains four errors that are preventing the test from passing. Debug and correct each error. As you identify the errors, fill out a description of the problem and an explanation of the root cause and your fix in the section below.

Description: The get_previous() method does not return zero when there is no previous value.

Explanation: The only situation in which there wouldn't be a previous value is when the method is trying to find the previous value of the first value in the list -- by definition, it doesn't have a previous value. To fix it, I set up a conditional where, if the index of the value is 0, the method should just return 0.

Description: The test throws an error about an index value being out of range.

Explanation: When using enumerate(), the first variable made available is the index. The variables were misnamed, which I was able to verify by printing the variables with a message identifying them. To solve this, I flipped the names so that the variables within this method would be defined semantically.

Description: The tests throw an error: "TypeError: 'int' object is not iterable" in line 32.

Explanation: The sum() method in Python requires the first argument to be iterable, like a list or tuple. Since in this line, we are just trying to add one number to another, it makes more sense to use the addition operator.

Description: The test is failing because the output is not what is expected.

Explanation: The subclass Transformer was being defined as an extention of both ParentA and ParentB. Transformer should only have one parent class.

Also, based on the output of the test, it looks like Transformer was being treated as a child of the ParentA superclass. Since this was not producing the desired output, I tried making ParentB the superclass. This made Transformer pass the test.