How to cover TypeORM @Column decorator with Jest unit testing?

Question

I want to Unit and e2e test my applications as much as possible and my goal is a coverage of 101%. Problem right now with my setup is, that the @Column decorator from typeorm uses an arrow function to set a default value like the current timestamp on a database update. This arrow function is not covered with jest test coverage. Message is: statement not covered

I run the code coverage with: jest --coverage. My versions:

"jest": "^24.9.0",
"typeorm": "^0.2.20"

Jest configuration within package.json:

{
  "jest": {
    "moduleFileExtensions": [
      "js",
      "json",
      "ts"
    ],
    "rootDir": "src",
    "testRegex": ".spec.ts$",
    "transform": {
      "^.+\\.(t|j)s$": "ts-jest"
    },
    "coverageDirectory": "../build/coverage",
    "testEnvironment": "node",
    "coverageThreshold": {
      "global": {
        "branches": 80,
        "functions": 80,
        "lines": 80,
        "statements": -10
      }
    }
  },
}

My entity looks like this:

import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';

@Entity()
export class Role {
    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    tenantId: number;

    @Column({ type: 'timestamp', update: false, default: () => 'CURRENT_TIMESTAMP()' })
    createdAt: Date;

    @Column({ type: 'timestamp', default: () => 'CURRENT_TIMESTAMP()', onUpdate: 'CURRENT_TIMESTAMP()' })
    updatedAt: Date;
}

Coverage for this entity:

(to post an image i need 10 reputation -.-): https://i.ibb.co/FYQgstP/Screenshot-2019-11-07-11-46-45.png

Answer 1

This is the solution that worked for me, based off of @JayMcDoniel's answer.

• database type: postgreSQl
• testing: jest/chai

Functions class:

  export abstract class EntityDefaultFunctions {
    public static defaultNull = (): string => 'NULL';
    public static defaultZero = (): string => '0';
  }

Tests:

  expect(EntityDefaultFunctions.defaultNull()).to.equal('NULL');
  expect(EntityDefaultFunctions.defaultZero()).to.equal('0');

Example Entity Column definition:

  @Column('text', {
    default: EntityDefaultFunctions.defaultNull,
    name: 'somePropertyName'
  })