• Work in a fork of this repository
• Work in a branch on your fork
• Write all of your code in a directory named lab- + <your name> e.g. lab-susan
• Open a pull request to this repository
• Submit on canvas a question and observation, how long you spent, and a link to your pull request

• Jest Getting Started
• Jest Globals
• Jest Expect

Configure the root of your repository with the following files and directories. Thoughfully name and organize any aditional configuration or module files.

• README.md - contains documentation
• .gitignore - contains a robust .gitignore file
• .eslintrc - contains the course linter configuratoin
• .eslintignore - contains the course linter ignore configuration
• lib/ - contains module definitions
• test/ - contains unit tests

Create a NodeJS module in the lib/ directory named greet.js that exports a single function.

• The greet function should have a single parameter (arity of one) that should expect a string as it's input
• The greet function should return the input name, concatenated with "hello ": eg. ("hello susan")
• The greet function should return null if the input is not a string

Create a NodeJS module in the lib/ directory named arithmetic.js that exports an object. This module should have add and sub methods that implement addition and subtraction.

• The add method should have an arity of two (define two paramiters)
  • If either parameter is a non-number the function should return null
  • Else return the sum of the 2 numbers
• The sub method should have an arity of two (define two paramiters)
  • If either parameter is a non-number the function should return null
  • Else return the second paramiter subtracted from the first paramiter

• Create a NodeJS module in the lib/ directory named array-util.js that exports an object. This module should have the following methods:
  • A sum function that accepts an array and returns the total of all the elements in the array.
  • return 0 is the array is empty
  • A min function that returns the smallest value from an array
  • return undefined if the array is empty
  • An isSorted function that returns true if all the elements in the array appear in ascending order.
  • return true if the array is empty

• Write a test that expects the greet module to return null when you supply non string values
• Write a test the expects the greet module to return 'hello world'
  • This should happen when invoked with 'world' as the first argument

• Test each method for proper use (invoded with number arguments)
• Test each method for inproper use (invoded with one or more non-numner arguments)

• Test sum to make sure it returns 0 for an empty array.

• Test sum to make sure it adds positive numbers properly

• Test sum to make sure it adds nagative numbers properly

• Test min to make sure it returns undefined for an empty array

• Test min to make sure it returns the smallest number when the array only has one value

• Test min to make sure it returns the smallest number in a small collection of numbers

• Test min to make sure it returns the smallest number when there's a collection of both positive and negative numbers

• Test isSorted to make sure it returns true for an empty array

• Test isSorted to make sure it returns true for a single-element array

• Test isSorted to make sure it returns true for a sorted array

• Test isSorted to make sure it returns false for an unsorted array

In your README.md describe the exported values of each module defined in your lib/ directory. Every function description should include it's airty (expected number of paramiters), the expected data for each parameter (data-type and limitations), and the it's output behavior (for both valid and invalid use). Feel free to write any additional information in your README.md.

• Modify the isSorted array utility to return true if the array is sorted in either ascending or descending order.