This PropertyWrapper allow you to force a value when decoding a property

MockCodable.swift

import Foundation

/// This allow to force a default value when using codable
/// This will force `isEditMode` to always have `false` when decoding it
/// @MockCodable(defaultValue: false) public var isEditMode: Bool = true
@propertyWrapper 
public struct MockCodable<Value> {
  private var value: Value
  private var defaultValue: Value
  
  public init(wrappedValue: Value, defaultValue: Value) {
    self.value = wrappedValue
    self.defaultValue = defaultValue
  }
  
  public var wrappedValue: Value {
    get { value }
    set { self.value = newValue }
  }
}

extension MockCodable: Decodable where Value: Decodable {
  public init(from decoder: Decoder) throws {
    let container = try decoder.singleValueContainer()
    let extracted = try container.decode(Value.self)
    self.value = extracted
    self.defaultValue = extracted
  }
}

extension MockCodable: Encodable where Value: Encodable {
  public func encode(to encoder: Encoder) throws {
    var container = encoder.singleValueContainer()
    try container.encode(self.defaultValue)
  }
}

extension MockCodable: Equatable where Value: Equatable {
  public static func == (lhs: MockCodable<Value>, rhs: MockCodable<Value>) -> Bool {
    lhs.wrappedValue == rhs.wrappedValue
  }
}

extension MockCodable: Hashable where Value: Hashable {
  public func hash(into hasher: inout Hasher) {
    hasher.combine(wrappedValue)
  }
}