struct ChangePasswordRequest: Encodable {
    var email: String
    var newPassword: String
    var token: String
}

import XCTest
@testable import MyProject

class ChangePasswordRequestTests: XCTestCase {

    var changePasswordRequest: ChangePasswordRequest!

    override func tearDown() {
        // Put teardown code here. This method is called after the invocation of each test method in the class.
        changePasswordRequest = nil
        super.tearDown()
    }

    func testChangePasswordRequest() {

        // given
        let email = "abc@def.com.br"
        let newPassword = "abc123"
        let token =
        """
        rF1rHbYVCpcfyo6K2e7Q68QvKYdeOMt0vDXYehggGU3kx8XiuGmQylXabxbGAyUmSK9RnbL
        """

        // when
        changePasswordRequest = ChangePasswordRequest(email: email, newPassword: newPassword, token: token)

        let requestJSON = """
        {"email":"(email)","token":"(token)","newPassword":"(newPassword)"}
        """

        changePasswordRequest = ChangePasswordRequest(email: email, newPassword: newPassword, token: token)
        guard let encodedRequest = try? JSONEncoder().encode(changePasswordRequest) else {
            XCTFail()
            return
        }

        // then
        XCTAssertEqual(String(data: encodedRequest, encoding: .utf8)!, requestJSON, "Any JSON key differs from model.")

    }

}

class UserManager: UserManagerType {
 let database: DatabaseType
 init(database: DatabaseType) {
  self.database = database
 }

 func getUser(withId id: String) -> User? {
    return database.getItem(withPredicate: "id == (id)")
 }

 func getAdmins() -> [User] {
    return database.getItems(withPredicate: "type == admin")
 }
}

protocol DatabaseType {
   func getItems(withPredicate predicate: String) -> [User]
   func getItem(withPredicate predicate: String) -> User?
}

// create mock for database.
// Try to avoid any external dependencies in tests
class DatabaseMock: DatabaseType {
 var itemsToReturn: [User] = []
 var userToReturn: User?

 func getItems(withPredicate predicate: String) -> [User] {
   return itemsToReturn
 }

 func getItem(withPredicate predicate: String) -> User? {
   return userToReturn
 }
}

// actual test case
class UserManagerTests: XCTestCase {
  var database: DatabaseMock = DatabaseMock()
  var manager: UserManager!
  // setup before each test
  func setUp() {
    database = DatabaseMock()
    manager = UserManager(database: database)
  }

  func testReturnsCorrectUserForId() {
    let expectedUser = User(id: "123")
    database.userToReturn = expectedUser
    let actualUser = manager.getUser(withId: "123")
    XCTAssertNotNil(actualUser)
    XCTAsseerEqual(actualUser.id, expectedUser.id)
  }

  // other tests ...
}