diff --git a/.gitignore b/.gitignore
index 4fb759d..61a2fbc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 node_modules
 dist
 npm-debug.log
-coverage
\ No newline at end of file
+coverage
+/vscode
\ No newline at end of file
diff --git a/.vscode/launch.json b/.vscode/launch.json
new file mode 100644
index 0000000..1176953
--- /dev/null
+++ b/.vscode/launch.json
@@ -0,0 +1,29 @@
+{
+  // Use IntelliSense to learn about possible attributes.
+  // Hover to view descriptions of existing attributes.
+  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "type": "node",
+      "name": "vscode-jest-tests.v2",
+      "request": "launch",
+      "args": [
+        "--runInBand",
+        "--watchAll=false",
+        "--testNamePattern",
+        "${jest.testNamePattern}",
+        "--runTestsByPath",
+        "${jest.testFile}"
+      ],
+      "cwd": "${workspaceFolder}",
+      "console": "integratedTerminal",
+      "internalConsoleOptions": "neverOpen",
+      // "disableOptimisticBPs": true,
+      "program": "${workspaceFolder}/node_modules/.bin/jest",
+      "windows": {
+        "program": "${workspaceFolder}/node_modules/jest/bin/jest"
+      }
+    }
+  ]
+}
diff --git a/src/index.test.ts b/src/index.test.ts
index f3b13a9..e0410de 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -1,7 +1,111 @@
-//write tests here
+import { UserAPI, IUser, IUserRecord } from './index'
 
-describe('Tests will go here!', () => {
-  it('should pass', () => {
-    expect(true).toBeTruthy()
+const seedUsers: Readonly<IUserRecord> = {
+  "1": { id: "1", name: "andy", favColor: "blue", age: 247 },
+  "2": { id: "2", name: "Andy",  favColor: "purple", age: 150 },
+  "3": { id: "3", name: "Sarah", favColor: "Blue", age: 200} 
+}
+
+describe(UserAPI, () => {
+  const userAPI = new UserAPI(seedUsers)
+
+  it('check that UserAPI is initialized', () => {
+    expect(userAPI).toBeInstanceOf(UserAPI)
+  })
+
+  describe('getUser()', () => {
+    const userAPI = new UserAPI(seedUsers)
+
+    it("getUsers() returns intitial seed data", () => {
+      const actual = userAPI.getUsers()
+      const expected = Object.values(seedUsers)
+      expect(actual).toEqual(expected)
+    })
+  })
+  
+  describe('addUser()', () => {
+    const userAPI = new UserAPI(seedUsers)
+
+    it('addUser() adds new user to the dataset', () => {
+      const user: IUser = { name: "Sarah", favColor: "Blue", age: 150 } 
+      const newUser: IUser = userAPI.addUser(user)
+      const actual: ReadonlyArray<IUser> = userAPI.getUsers()
+      const expected: ReadonlyArray<IUser> = Object.values({...seedUsers, newUser})
+      expect(actual).toEqual(expected)
+    })
+    
+    it("addUser() throws error when duplicating user info", () => {
+      const userDuplicate = { name: "andy", favColor: "blue", age: 247 }
+      const actual= () => {userAPI.addUser(userDuplicate)}
+      expect(actual).toThrow(Error)
+    })
+    
+    it("addUser() throws error supplied with pre-existing user.id", () => {
+      const userWithId = seedUsers['1']
+      const actual = () => {userAPI.addUser(userWithId)}
+      expect(actual).toThrow(Error)
+    })
+  })
+  
+  describe('getUserById()', () => {
+    const userAPI = new UserAPI(seedUsers)
+
+    it('getUserById() returns expected user', () => {
+      const actual: IUser = userAPI.getUserById("2")
+      const expected: IUser = seedUsers['2']
+      expect(actual).toEqual(expected)
+    })
+  
+    it('getUserById() throws error if user with id is not found', () => {
+      const actual = () => userAPI.getUserById("100")
+      expect(actual).toThrow(ReferenceError)
+    })
+  })
+  
+  describe('deleteUserById()', () => {
+    const userAPI = new UserAPI(seedUsers)
+
+    it('deleteUserById() deletes user with given id', () => {
+      userAPI.deleteUserById("1")
+      const actual: ReadonlyArray<IUser> = userAPI.getUsers()
+      const expected: ReadonlyArray<IUser> = [ seedUsers['2'], seedUsers['3'] ]
+
+      expect(actual).toEqual(expected)
+    })
+    
+    it('deleteUserById() throws error if user is not found', () => {
+      const actual =  () => {userAPI.deleteUserById("100")}
+      expect(actual).toThrow(ReferenceError)
+    })
+  })
+  
+  describe('searchUserbyName()', () => {
+    const userAPI = new UserAPI(seedUsers)
+
+    it('searchUserByName() returns all instances of given name, independant of capitals', () => {
+      const actual: ReadonlyArray<IUser> = userAPI.searchUserByName("Andy")
+      const expected: ReadonlyArray<IUser>= [ seedUsers['1'], seedUsers['2'] ]
+      expect(actual).toEqual(expected)
+    })
+    
+    it('searchUserByName() throws error if no user is found', () => {
+      const actual =  () => userAPI.searchUserByName("Jessica")
+      expect(actual).toThrow(ReferenceError)
+    })
+  })
+  
+  describe('searchUserFavoriteColor()', () => {
+    const userAPI = new UserAPI(seedUsers)
+
+    it('searchUserByFavoriteColor() returns all instances users with given fav color, independant of capitals', () => {
+      const actual: ReadonlyArray<IUser> = userAPI.searchUsersByFavoriteColor("blue")
+      const expected: ReadonlyArray<IUser> = [ seedUsers['1'], seedUsers['3'] ]
+      expect(actual).toEqual(expected)
+    })
+    
+    it('searchUserByFavoriteColor() throws error if no user is found with given fav color', () => {
+      const actual =  () => userAPI.searchUsersByFavoriteColor("Pink")
+      expect(actual).toThrow(ReferenceError)
+    })
   })
-})
\ No newline at end of file
+})
diff --git a/src/index.ts b/src/index.ts
index bb6b54e..e3e45bf 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1 +1,80 @@
-//Define class here
\ No newline at end of file
+export interface IUser {
+  readonly id?: string
+  readonly name: string
+  readonly favColor: string
+  readonly age: number
+}
+
+export type IUserRecord = Record<string, IUser>
+
+export class UserAPI {
+  private _users: Readonly<IUserRecord>
+
+  constructor(seedData: IUserRecord = {}) {
+    this._users = {...seedData}
+  } 
+
+  private _assignId(): string {
+    const id: Readonly<string> = Date.now().toString() + Math.floor(Math.random()*100)
+    return id
+  }
+  
+  addUser(user: IUser): IUser {
+    if (user.id) {
+      throw new SyntaxError("Please resubmit without pre-exisitng ID field.")
+    } 
+    const result = (Object.values(this._users)).some( existingUser => (
+      existingUser.name.toLowerCase() === user.name.toLowerCase() && 
+      existingUser.favColor.toLowerCase() === user.favColor.toLowerCase() && 
+      existingUser.age === user.age
+    ))
+    
+    if (result) {
+      throw new Error("A user with those properties already exists in the database.")
+    } 
+
+    const newUser = {...user, id: this._assignId()}
+    this._users = {...this._users, [newUser.id]: newUser}
+    return newUser
+  }
+
+  getUserById(id: string): IUser {
+    if (this._users[id]) {
+      return this._users[id]
+    }
+    throw new ReferenceError(`No user found with id ${id}.`)
+  }
+
+  getUsers(): Array<IUser> {
+    if (this._users === null || this._users === undefined) {
+      throw new Error(`User Dataset not found`)
+    }
+    return Object.values(this._users)
+  }
+
+  deleteUserById(id: string): IUser {
+    if (this._users[id]) {
+      const { [id]: deletedUser, ...rest } = this._users
+      this._users = {...rest}
+      return deletedUser
+    } 
+    throw new ReferenceError(`No user found with id ${id}.`)
+  }
+
+  searchUserByName(name: string): ReadonlyArray<IUser> {
+    const users = Object.values(this._users).filter( user => user.name.toLowerCase() === name.toLowerCase())
+    
+    if (users.length) {
+      return users
+    } 
+    throw new ReferenceError(`No user found with name ${name}`)
+  }
+
+  searchUsersByFavoriteColor(color: string): ReadonlyArray<IUser> {
+    const users = Object.values(this._users).filter( user => user.favColor.toLowerCase() === color.toLowerCase())
+    if (users.length) {
+      return users
+    } 
+    throw new ReferenceError(`No users favorite color is ${color}`)
+  }
+}