Final answer:
To setup Mocha and practice TDD for three different functions: reversing words in an array, number manipulation using a class, and filtering words without built-in functions, you need to set up the file structure, install dependencies, and write tests using Mocha. Follow the Red-Green-Refactor approach to implement each function and verify its functionality.
Step-by-step explanation:
a) Reversing words in an array:
To set up the file structure and install the necessary dependencies to run Mocha, you need to have Node.js installed on your computer. Once Node.js is installed, you can use the npm (Node Package Manager) command in the terminal to initialize a new project and install Mocha. To practice TDD for a function that reverses words in an array, you can write test cases in Mocha to check the expected outputs for different inputs. Then, you can implement the function step-by-step, starting with a failing test case (Red), making it pass (Green), and finally refactoring the code.
b) Number Manipulation Class:
Similar to the first case, you can set up the file structure and install the dependencies for Mocha. TDD can be used to develop a Number Manipulation class that performs multiplication, addition, subtraction, and division. Write the test cases for each operation and verify the expected outputs. Implement the class by following the Red-Green-Refactor approach.
c) Filtering words without using built-in filter function:
For this case, you need to write a function that takes in an array of words and filters out words that end in 'er'. Again, start with the file structure and Mocha setup. Then, write test cases that cover different scenarios, including words that should be filtered out. Implement the function, run the tests, and refactor if necessary.