feat: Setup Unit Tests for Backend

backend/.gitignore

@@ -2,5 +2,6 @@
 /.env
 /build/
 
+coverage
 # emacs
 *~

backend/jest.config.js

@@ -0,0 +1,6 @@
+/** @type {import('ts-jest/dist/types').InitialOptionsTsJest} */
+module.exports = {
+  verbose: true,
+  preset: 'ts-jest',
+  collectCoverageFrom: ['src/**/*.ts', '!**/node_modules/**', '!**/?(*.)+test.ts'],
+}

backend/package.json

@@ -12,9 +12,11 @@
     "clean": "tsc --build --clean",
     "start": "node build/index.js",
     "dev": "nodemon -w src --ext ts --exec ts-node src/index.ts",
-    "lint": "eslint . --ext .js,.ts"
+    "lint": "eslint . --ext .js,.ts",
+    "test": "jest --coverage"
   },
   "dependencies": {
+    "@types/jest": "^27.0.2",
     "apollo-server-express": "^2.25.2",
     "axios": "^0.21.1",
     "class-validator": "^0.13.1",
@@ -22,9 +24,11 @@
     "dotenv": "^10.0.0",
     "express": "^4.17.1",
     "graphql": "^15.5.1",
+    "jest": "^27.2.4",
     "jsonwebtoken": "^8.5.1",
     "mysql2": "^2.3.0",
     "reflect-metadata": "^0.1.13",
+    "ts-jest": "^27.0.5",
     "type-graphql": "^1.1.1",
     "typeorm": "^0.2.37"
   },

backend/src/util/decay.test.ts

@@ -0,0 +1,11 @@
+import decayFunction from './decay'
+
+describe('utils/decay', () => {
+  it('has base 0.99999997802044727', () => {
+    const now = new Date()
+    now.setSeconds(1)
+    const oneSecondAgo = new Date(now.getTime())
+    oneSecondAgo.setSeconds(0)
+    expect(decayFunction(1.0, oneSecondAgo, now)).toBe(0.99999997802044727)
+  })
+})

backend/src/util/decay.ts

@@ -1,4 +1,6 @@
 export default function (amount: number, from: Date, to: Date): number {
+  // what happens when from > to
+  // Do we want to have negative decay?
   const decayDuration = (to.getTime() - from.getTime()) / 1000
   return amount * Math.pow(0.99999997802044727, decayDuration)
 }