Unit test for a password-change request

Question

I'm studying unit testing in swift and I would like to know if I'm doing the right way.

Here I have the model

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

And here the unit test

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 = "[email protected]"
 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.")
 }
}

I never worked with unit test. It's possible to improve this test?

Answer 1

Some hints on Unit tests.

• Use dependency injection to make testing easier
• Create mocks to eliminate all external dependencies in tests
• Test units of code (functions, methods, classes)

Example of testable class:

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?
} 

Tests:

// 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 ...
}

This is not the best example (because UserManager is just a wrapper around database) but I hope you have got some ideas of how write unit tests

Answer 2

You should think about WHAT you test.

You just test in your UnitTest the Json encoder. But i think the json encoder is still good tested and you not need to test it again.

You should test business logic (methods/functions) you have written and cover the code with the test