Swift Test case Falling with Expectation - swift

Question

I am trying to run test case for Failure response . I have an empty json file into project and named it FailureResponse . This file is empty . I trying to count the number of array is empty for example ..
XCTAssertTrue(schools.count==0)
It should pass the test because the json file is empty .
same result fields like school name and School location etc but the problem is it showing error ..
testFailure(): Asynchronous wait failed: Exceeded timeout of 6 seconds, with unfulfilled expectations: "waiting for response".
View Model code...
import Foundation
import Combine
class ViewModel {
private let networkManager = NetworkManager()
#Published private(set) var school = [School]()
func getSchools() {
loadMoreSchools()
}
func loadMoreSchools() {
let newURL = NetworkURLs.baseURL
networkManager
.getModel([School].self, from: newURL) { [weak self] result in
switch result {
case .success(let schoolResponse):
self?.school = schoolResponse
print(schoolResponse)
case .failure(let error):
print(error)
}
}
}
func getSchoolName(by row: Int) -> String {
let schoolName = school[row]
return schoolName.schoolName.uppercased()
}
func getSchoolLocation(by row: Int) -> String {
return "\(school[row].location)"
}
}
Here is my Mock service call ..
class MockService: NetworkManagerProtocol {
var data: Data?
func getModel<Model>(_ type: Model.Type, from url: String, completion: #escaping (Result<Model, Alomafire_Project.NetworkError>) -> ()) where Model : Decodable, Model : Encodable {
if let data = data {
do {
let result = try JSONDecoder().decode(type, from: data)
completion(.success(result))
} catch (let error){
print(error)
}
}
}
}
Here is code for call the local Jason ..
func getData(json: String) throws -> Data {
guard let url = Bundle(for: Alomafire_ProjectTests.self).url(forResource: json, withExtension: "json")
else { return Data() }
return try Data(contentsOf: url)
}
Here is the test case ....
func testFailure() throws {
// Given
mockService.data = try getData(json: "FailureResponse")
var schools: [School] = []
let expectation = expectation(description: "waiting for response")
// When
viewModel?
.$school
.dropFirst()
.sink(receiveValue: { result in
schools = result
expectation.fulfill()
})
.store(in: &subscribers)
// viewModel?.getSchools()
// Then
waitForExpectations(timeout: 10.0)
XCTAssertTrue(schools.count==0)
}
Here is the debug result . it return 0 ..
Here is the screenshot of the result ..

Answer 1

You mention in the question that "the json file is empty." If that is the case, then this test will fail. The MockService assumes that the Data pulled from the json file will be decodable to the type requested. If it isn't the getModel(_:from:completion:) will never call the completion and the test will not complete in the specified time limit. Solve this by calling the completion closure even when the JSONDecoder response with an error.
Also, even if that mock emits the error properly, your ViewModel doesn't do anything with it that would cause the schools type to update.