implement a simplest schema test

jest.config.js

@@ -0,0 +1,4 @@
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+};

package.json

@@ -4,7 +4,8 @@
     "description": "",
     "main": "src/app.js",
     "scripts": {
-        "dev": "ts-node-dev --respawn src/app.ts"
+        "dev": "ts-node-dev --respawn src/app.ts",
+        "test": "jest"
     },
     "keywords": [],
     "author": "",
@@ -17,6 +18,10 @@
     },
     "devDependencies": {
         "@types/graphql": "^14.2.0",
+        "@types/jest": "^24.0.13",
+        "class-transformer": "^0.2.3",
+        "jest": "^24.8.0",
+        "ts-jest": "^24.0.2",
         "ts-node-dev": "^1.0.0-pre.39",
         "typescript": "^3.5.1"
     }

src/User.ts

@@ -1,4 +1,4 @@
-import { ObjectType, Field } from "type-graphql"
+import { Field, ObjectType } from "type-graphql";
 
 @ObjectType()
 export class User {

src/User/UserResolver.spec.ts

@@ -0,0 +1,22 @@
+import { callSchema } from "../callSchema";
+
+const usersQuery = `
+query {
+    users {
+        id
+    }
+}`
+
+describe("user resolver", () => {
+    it("should return an empty array when no users are in sample", async () => {
+        const response = await callSchema({
+            source: usersQuery,
+        })
+
+        expect(response).toMatchObject({
+            data: {
+                users: [],
+            },
+        })
+    })
+})

src/User/UserResolver.ts

@@ -1,13 +1,13 @@
-import "reflect-metadata"
-import { Resolver, Query } from "type-graphql"
-import { User } from "../User"
+import "reflect-metadata";
+import { Query, Resolver } from "type-graphql";
+import { User } from "../User";
 
 @Resolver()
 export class UserResolver {
-    private recipesCollection: User[] = []
+    private usersCollection: User[] = []
 
     @Query(returns => [User])
     async users() {
-        return await this.recipesCollection
+        return await this.usersCollection
     }
 }

src/app.ts

@@ -1,6 +1,6 @@
-import { ApolloServer } from "apollo-server"
-import { buildSchema } from "type-graphql"
-import { UserResolver } from "./User/UserResolver"
+import { ApolloServer } from "apollo-server";
+import { buildSchema } from "type-graphql";
+import { UserResolver } from "./User/UserResolver";
 
 const PORT = process.env.PORT || 4000
 

src/callSchema.ts

@@ -0,0 +1,18 @@
+import { graphql, GraphQLSchema } from "graphql"
+import { createSchema } from "./createSchema"
+
+interface Options {
+    source: string
+}
+
+let schema: GraphQLSchema
+
+export const callSchema = async ({ source }: Options) => {
+    if (!schema) {
+        schema = await createSchema()
+    }
+    return graphql({
+        schema,
+        source,
+    })
+}

src/createSchema.ts

@@ -0,0 +1,7 @@
+import { buildSchema } from "type-graphql";
+import { UserResolver } from "./User/UserResolver";
+
+export const createSchema = () =>
+    buildSchema({
+        resolvers: [UserResolver],
+    })