BindingTester

Trying to implement Unit Tests for @Binding properties in a ViewModel

ViewModel to be tested

class SheetViewModel: ObservableObject {

  @Binding var isPresented: Bool
  
  func onClose() {
    isPresented = false // To be unit tested
  }
  
  init(isPresented: Binding<Bool>) {
    _isPresented = isPresented

Unit tests try out – not working

func test1() {
  let viewModel = SheetViewModel(isPresented: .constant(true))

  XCTAssertTrue(viewModel.isPresented)
  viewModel.onClose()
  XCTAssertFalse(viewModel.isPresented)
}


func test2() {
  @State var isSheetDisplayed: Bool = true
  let viewModel = SheetViewModel(isPresented: $isSheetDisplayed) // Accessing State's value outside of being installed on a View.

  XCTAssertTrue(viewModel.isPresented)
  viewModel.onClose()
  XCTAssertFalse(viewModel.isPresented)
}


func test3() {
  let isSheetDisplayed: Binding<Bool> = .constant(true)
  let viewModel = SheetViewModel(isPresented: isSheetDisplayed)

  XCTAssertTrue(viewModel.isPresented)
  viewModel.onClose()
  XCTAssertFalse(viewModel.isPresented)
}

GitHub

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