test: add initial set of unit tests

.eslintrc

@@ -16,6 +16,9 @@
     "no-undef": "off",
     "no-use-before-define": "off",
     "no-unused-vars": "off",
-    "@typescript-eslint/no-unused-vars": ["error"]
+    "@typescript-eslint/no-unused-vars": ["error"],
+    "max-lines-per-function": "off",
+    "consistent-return": "off",
+    "jest/no-if": "off"
   }
 }

.gitignore

@@ -3,3 +3,6 @@ node_modules/
 
 # Build output directory
 dist
+
+# Test coverage directory
+coverage

jest.config.js

@@ -0,0 +1,6 @@
+/** @type {import('ts-jest').JestConfigWithTsJest} */
+module.exports = {
+  preset: "ts-jest",
+  testEnvironment: "node",
+  testRegex: ".+\\.test\\.ts$",
+};

package.json

@@ -9,9 +9,10 @@
     "build": "npm-run-all build:cjs build:esm",
     "build:cjs": "tsc -p tsconfig.build.json",
     "build:esm": "tsc -p tsconfig.esm.json",
+    "test": "prisma generate && jest",
     "lint": "eslint ./src  --fix --ext .ts",
     "typecheck": "npm run build:cjs -- --noEmit && npm run build:esm -- --noEmit",
-    "validate": "kcd-scripts validate lint,typecheck",
+    "validate": "kcd-scripts validate lint,typecheck,test",
     "semantic-release": "semantic-release",
     "doctoc": "doctoc ."
   },
@@ -32,14 +33,22 @@
     "@prisma/client": "*"
   },
   "devDependencies": {
+    "@prisma/client": "^4.8.1",
+    "@types/faker": "^5.5.9",
+    "@types/jest": "^29.2.5",
     "@types/lodash": "^4.14.185",
     "@typescript-eslint/eslint-plugin": "^4.14.0",
     "@typescript-eslint/parser": "^4.14.0",
     "doctoc": "^2.2.0",
+    "dotenv": "^16.0.3",
     "eslint": "^7.6.0",
+    "faker": "^5.0.0",
+    "jest": "^29.3.1",
     "kcd-scripts": "^5.0.0",
     "npm-run-all": "^4.1.5",
+    "prisma": "^4.8.1",
     "semantic-release": "^17.0.2",
+    "ts-jest": "^29.0.3",
     "ts-node": "^9.1.1",
     "typescript": "^4.1.3"
   },

prisma/schema.prisma

@@ -0,0 +1,50 @@
+generator client {
+  provider = "prisma-client-js"
+}
+
+datasource db {
+  provider = "postgresql"
+  url      = env("DATABASE_URL")
+}
+
+model User {
+  id      Int       @id @default(autoincrement())
+  email   String    @unique
+  name    String?
+  posts   Post[]
+  profile Profile?
+  comments Comment[]
+}
+
+model Post {
+  id        Int       @id @default(autoincrement())
+  createdAt DateTime  @default(now())
+  updatedAt DateTime  @updatedAt
+  published Boolean   @default(false)
+  title     String
+  content   String?
+  author    User      @relation(fields: [authorId], references: [id])
+  authorId  Int
+  comments  Comment[]
+}
+
+model Comment {
+  id          Int       @id @default(autoincrement())
+  createdAt   DateTime  @default(now())
+  updatedAt   DateTime  @updatedAt
+  content     String
+  author      User      @relation(fields: [authorId], references: [id])
+  authorId    Int
+  post        Post      @relation(fields: [postId], references: [id])
+  postId      Int
+  repliedTo   Comment?  @relation("replies", fields: [repliedToId], references: [id])
+  repliedToId Int?
+  replies     Comment[] @relation("replies")
+}
+
+model Profile {
+  id     Int     @id @default(autoincrement())
+  bio    String?
+  user   User    @relation(fields: [userId], references: [id])
+  userId Int     @unique
+}

src/index.ts

@@ -1,5 +1,5 @@
 /* eslint-disable import/no-unresolved */
-// @ts-expect-error unable to generate prisma client before building
+// @ts-ignore unable to generate prisma client before building
 import { Prisma } from '@prisma/client';
 
 import get from 'lodash/get';
@@ -9,20 +9,8 @@ if (!Prisma.dmmf) {
   throw new Error('Prisma DMMF not found, please generate Prisma client using `npx prisma generate`');
 }
 
-type Field = {
-  kind:  "scalar" | "object" | "enum" | "list";
-  relationName?: string;
-  name: string;
-  type: string;
-}
-
-type Model = {
-  name: string;
-  fields: Field[];
-}
-
-const relationsByModel: Record<string, Field[]> = {};
-Prisma.dmmf.datamodel.models.forEach((model: Model) => {
+const relationsByModel: Record<string, Prisma.DMMF.Field[]> = {};
+Prisma.dmmf.datamodel.models.forEach((model: Prisma.DMMF.Model) => {
   relationsByModel[model.name] = model.fields.filter(
     (field) => field.kind === 'object' && field.relationName
   );
@@ -71,7 +59,7 @@ function isWriteOperation(key: any): key is NestedAction {
 
 function extractWriteInfo(
   params: NestedParams,
-  model: string,
+  model: Prisma.ModelName,
   argPath: string
 ): WriteInfo[] {
   const arg = get(params.args, argPath, {});
@@ -92,9 +80,9 @@ function extractWriteInfo(
 
 function extractNestedWriteInfo(
   params: NestedParams,
-  relation: Field
+  relation: Prisma.DMMF.Field
 ): WriteInfo[] {
-  const model = relation.type;
+  const model = relation.type as Prisma.ModelName;
 
   switch (params.action) {
     case 'upsert':