Supports "createMany" model method

src/factory.ts

@@ -6,6 +6,7 @@ import {
   EntityInstance,
   ModelDictionary,
   PrimaryKeyType,
+  RelationKind,
 } from './glossary'
 import { first } from './utils/first'
 import { executeQuery } from './query/executeQuery'
@@ -14,6 +15,7 @@ import { createModel } from './model/createModel'
 import { invariant } from './utils/invariant'
 import { updateEntity } from './model/updateEntity'
 import { OperationError, OperationErrorType } from './errors/OperationError'
+import { getRandomNumber } from './utils/getRandomNumber'
 
 /**
  * Create a database with the given models.
@@ -31,6 +33,7 @@ export function factory<Dictionary extends ModelDictionary>(
       modelName,
       props,
       db,
+      acc,
     )
     return acc
   }, {})
@@ -39,7 +42,12 @@ export function factory<Dictionary extends ModelDictionary>(
 function createModelApi<
   Dictionary extends ModelDictionary,
   ModelName extends string
->(modelName: ModelName, declaration: ModelDeclaration, db: Database) {
+>(
+  modelName: ModelName,
+  declaration: ModelDeclaration,
+  db: Database,
+  factory: FactoryAPI<Dictionary>,
+) {
   let modelPrimaryKey: PrimaryKeyType
 
   const api: ModelAPI<Dictionary, ModelName> = {
@@ -70,6 +78,36 @@ function createModelApi<
 
       return entity
     },
+    createMany(count, options) {
+      const resolvedCount = count || getRandomNumber(5, 10)
+      const getRelations = options?.relations
+        ? () =>
+            Object.entries(options.relations).reduce((acc, [key, count]) => {
+              const propDeclaration = declaration[key]
+
+              if ('__type' in propDeclaration) {
+                const isManyOfRelationType =
+                  propDeclaration.__type === RelationKind.ManyOf
+                const relationalModel = factory[propDeclaration.modelName]
+                const records = isManyOfRelationType
+                  ? relationalModel.createMany(count as number)
+                  : relationalModel.create()
+
+                acc[key] = records
+              }
+
+              return acc
+            }, {})
+        : null
+
+      const createdEntities = new Array(resolvedCount)
+        .fill(null)
+        .map<EntityInstance<any, any>>(() => {
+          return api.create(getRelations?.())
+        })
+
+      return createdEntities
+    },
     count(query) {
       if (!query) {
         return db[modelName].size

src/glossary.ts

@@ -105,6 +105,14 @@ export interface ModelAPI<
   create(
     initialValues?: Partial<Value<Dictionary[ModelName], Dictionary>>,
   ): EntityInstance<Dictionary, ModelName>
+  /**
+   * Create multiple entities for the model.
+   * @param count Amount of models to create.
+   */
+  createMany(
+    count?: number,
+    options?: CreateManyOptions<Dictionary[ModelName]>,
+  ): EntityInstance<Dictionary, ModelName>[]
   /**
    * Return the total number of entities.
    */
@@ -182,4 +190,19 @@ export type Value<
     : ReturnType<T[K]>
 }
 
+type SubType<P, Condition> = Pick<
+  P,
+  {
+    [K in keyof P]: P[K] extends Condition ? K : never
+  }[keyof P]
+>
+
+interface CreateManyOptions<T extends Record<string, any>> {
+  relations: {
+    [K in keyof SubType<T, OneOf<any> | ManyOf<any>>]: T[K] extends ManyOf<any>
+      ? number
+      : boolean
+  }
+}
+
 export type Database = Record<KeyType, Map<string, EntityInstance<any, any>>>

src/utils/getRandomNumber.ts

@@ -0,0 +1,8 @@
+/**
+ * Return a random number in range.
+ * @param min The lowest number to return.
+ * @param max The highest number to return.
+ */
+export function getRandomNumber(min: number = 5, max: number = 50) {
+  return Math.floor(Math.random() * (max - min + 1) + min)
+}

test/model/createMany.test.ts

@@ -0,0 +1,64 @@
+import { name, random } from 'faker'
+import { factory, manyOf, oneOf, primaryKey } from '../../src'
+
+test('creates multiple entities with a fixed count', () => {
+  const db = factory({
+    user: {
+      id: primaryKey(random.uuid),
+      firstName: name.firstName,
+    },
+  })
+
+  db.user.createMany(5)
+
+  const allUsers = db.user.getAll()
+  expect(allUsers).toHaveLength(5)
+})
+
+test('allows to specify count of relational entities to create', () => {
+  const db = factory({
+    user: {
+      id: primaryKey(random.uuid),
+      country: oneOf('country'),
+      posts: manyOf('post'),
+    },
+    post: {
+      id: primaryKey(random.uuid),
+      title: random.words,
+    },
+    country: {
+      id: primaryKey(random.uuid),
+      name: random.word,
+    },
+  })
+
+  db.user.createMany(3, {
+    relations: {
+      /**
+       * @todo How to specify that multiple entities should reuse the same relational model?
+       * I.e. multiple users from the same country.
+       *
+       * @todo `Boolean` value of `oneOf` relation has no sense:
+       * an entity cannot be created without all relational models specified.
+       */
+      country: false,
+      posts: 2,
+    },
+  })
+
+  const allUsers = db.user.getAll()
+  const allPosts = db.post.getAll()
+  const allCountries = db.country.getAll()
+
+  expect(allUsers).toHaveLength(3)
+  // Each of 3 random "user" should have "2" posts created.
+  expect(allPosts).toHaveLength(6)
+  // Each of 3 random "user" should have its own "country".
+  expect(allCountries).toHaveLength(3)
+
+  allUsers.forEach((user, index) => {
+    expect(user.posts).toHaveLength(2)
+    expect(user.country).toHaveProperty('id', allCountries[index].id)
+    expect(user.country).toHaveProperty('name', allCountries[index].name)
+  })
+})