contains.test.js

const contains = require("./contains.js");

/*
Implement a function called contains that checks an object contains a
particular property

E.g. contains({a: 1, b: 2}, 'a') // returns true
as the object contains a key of 'a'

E.g. contains({a: 1, b: 2}, 'c') // returns false
as the object doesn't contains a key of 'c'
*/

// Acceptance criteria:

// Given a contains function
// When passed an object and a property name
// Then it should return true if the object contains the property, false otherwise

// Given an empty object
// When passed to contains
// Then it should return false
test("given an empty object, returns false", () => {
  expect(contains({}, "x")).toEqual(false);
});

// Given an object with properties
// When passed to contains with an existing property name
// Then it should return true
test("given an object with properties, returns true when passed to contains with an existing property name", () => {
  expect(
    contains({ gitName: "djebsoft", position: "cyf trainee" }, "gitName")
  ).toEqual(true);
});

// Given an object with properties
// When passed to contains with a non-existent property name
// Then it should return false
test("given an object with properties, returns false when passed to contains with a non-existent property name", () => {
  expect(
    contains({ gitName: "djebsoft", position: "cyf trainee" }, "age")
  ).toEqual(false);
});

// Given invalid parameters like an array
// When passed to contains
// Then it should return false or throw an error
// "length" is perfect for the test because it's real property on the array itself
test("given invalid parameters (array), returns false or throws an error", () => {
  expect(contains(["gitName", "age", "position"], "length")).toBe(false);
});

test("given invalid parameters (like null or undefined), returns false or throws an error", () => {
  expect(contains(null, "gitName")).toEqual(false);
});