Add tests for Checked

Tests/CheckedTests/CheckedTests.swift

@@ -1,5 +1,40 @@
-final class DecodedTests: XCTestCase {
-    func testChecked() throws {
-        // TODO: implement
+import Checked
+import Decoded
+import XCTest
+
+final class CheckedTests: XCTestCase {
+    func test_directPropertyAccess() throws {
+        struct Gadget: Decodable {
+            let name: Decoded<String>
+        }
+
+        let decoded = try decode(#"{"name":"arduino"}"#, as: Gadget.self)
+        let checked = try decoded.checked()
+        XCTAssertEqual(checked.name, "arduino")
+    }
+
+    func test_directPropertyAccess_nested() throws {
+        struct CarRequest: Decodable {
+            struct Engine: Decodable {
+                let cylinderVolume: Decoded<Double>
+            }
+            let engine: Decoded<Engine>
+        }
+
+        let decoded = try decode(#"{"engine":{"cylinderVolume": 0.9}}"#, as: CarRequest.self)
+        let checked = try decoded.checked()
+        XCTAssertEqual(checked.engine.cylinderVolume, 0.9)
+    }
+
+    func test_checkingFailedDecodingThrowsError() throws {
+        let decoded = try decode("0", as: String.self)
+
+        XCTAssertThrowsError(try decoded.checked()) { error in
+            guard error is DecodingErrors else {
+                XCTFail("expected error of type `DecodingErrors`")
+                return
+            }
+        }
     }
 }
+

Tests/CheckedTests/Helper/decode.swift

@@ -0,0 +1,8 @@
+import Decoded
+import Foundation
+
+let decoder = JSONDecoder()
+
+func decode<T: Decodable>(_ string: String, as _: T.Type = T.self) throws -> Decoded<T> {
+    try decoder.decode(Decoded<T>.self, from: string.data(using: .utf8)!)
+}