MVVM-C ViewModel Unit Tests

CountryListViewModelTests.swift

import XCTest
@testable import MVVMCDemo

class CountryListViewModelTests: XCTestCase {

    func testEndpoint() {
        let requestManager = LocalRequestManager()
        let sut = CountryListViewModel(requestManager: requestManager)
        sut.searchFor(keyword: "test")
        
        XCTAssertEqual(requestManager.endPoint?.urlPath, .name)
        XCTAssertEqual(requestManager.endPoint?.pathComponent, "test")
        XCTAssertEqual(requestManager.endPoint?.httpMethod, .get)
    }

    func testLoading() {
        let requestManager = LocalRequestManager()
        let sut = CountryListViewModel(requestManager: requestManager)

        let expectation = XCTestExpectation(description: "didChangeState() for CountryListViewModel should be called.")
        
        var changedStates: [(isLoading: Bool, loadingMessage: String?)] = []
        
        sut.didChangeState = { (isLoading, loadingMessage) in
            changedStates.append((isLoading, loadingMessage))
            
            if !isLoading && loadingMessage == nil {
                expectation.fulfill()
            }
        }
        
        sut.searchFor(keyword: "test")
        
        wait(for: [expectation], timeout: 2)
        
        let expectedStates = [(isLoading: true, loadingMessage:"Loading countries..."),
                              (isLoading: false, loadingMessage: nil)]
        
        XCTAssertEqual(changedStates.map{ $0.isLoading }, expectedStates.map{ $0.isLoading })
        XCTAssertEqual(changedStates.map{ $0.loadingMessage }, expectedStates.map{ $0.loadingMessage })
    }
    
    func testLoadingErrorDelegate() {
        let requestManager = LocalRequestManager()
        let sut = CountryListViewModel(requestManager: requestManager)

        let expectation = XCTestExpectation(description: "didFailLoading() for CountryListViewModel should be called.")
        
        let loadingErrorDelegate = LoadingErrorDelegateStub()
        loadingErrorDelegate.didFailLoadingCompletion = {
            expectation.fulfill()
        }
        sut.loadingErrorDelegate = loadingErrorDelegate
        
        sut.searchFor(keyword: "invalid search string")
        wait(for: [expectation], timeout: 2)
    }
    
    func testCountryListDatasource() {
        let requestManager = LocalRequestManager()
        let sut = CountryListViewModel(requestManager: requestManager)

        let expectation = XCTestExpectation(description: "didUpdate() for CountryListViewModel should be called.")
        
        sut.didUpdate = {
            expectation.fulfill()
            
            let expectedRowCount = 11
            XCTAssertEqual(sut.screenTitle, "Countries")
            XCTAssertEqual(sut.numberOfSections, 1)
            XCTAssertEqual(sut.numberOfRows(in: 0), expectedRowCount)
            
            let range = 0..<expectedRowCount
            range.forEach { (row) in
                
                XCTAssertNotNil(sut.country(at: IndexPath(row: row, section: 0)))
                _ = sut.itemForRow(at: IndexPath(row: row, section: 0))
            }
        }
        
        XCTAssertEqual(sut.screenTitle, "Countries")
        XCTAssertEqual(sut.numberOfSections, 1)
        XCTAssertEqual(sut.numberOfRows(in: 0), 0)
        
        sut.searchFor(keyword: "")
        
        wait(for: [expectation], timeout: 2)
    }
    
    func testCountryListDatasourceWithSearchString() {
        let requestManager = LocalRequestManager()
        let sut = CountryListViewModel(requestManager: requestManager)

        let expectation = XCTestExpectation(description: "didUpdate() for CountryListViewModel should be called.")
        
        sut.didUpdate = {
            expectation.fulfill()
            
            let expectedRowCount = 5
            XCTAssertEqual(sut.screenTitle, "Countries")
            XCTAssertEqual(sut.numberOfSections, 1)
            XCTAssertEqual(sut.numberOfRows(in: 0), expectedRowCount)
            
            for i in 0..<expectedRowCount {
                XCTAssertNotNil(sut.country(at: IndexPath(row: i, section: 0)))
                _ = sut.itemForRow(at: IndexPath(row: i, section: 0))
            }
        }
        
        XCTAssertEqual(sut.screenTitle, "Countries")
        XCTAssertEqual(sut.numberOfSections, 1)
        XCTAssertEqual(sut.numberOfRows(in: 0), 0)
        
        sut.searchFor(keyword: "ind")
        
        wait(for: [expectation], timeout: 2)
    }
}

private class LoadingErrorDelegateStub: CountryListViewModelLoadingErrorDelegate {
    
    var didFailLoadingCompletion: (() -> Void)?
    
    func didFailLoading(error: Error) {
        didFailLoadingCompletion?()
    }
}