test: add DynamicDecodable unit tests

Author: soumyamahunt

Package.swift

@@ -32,7 +32,7 @@ let package = Package(
             name: "DynamicCodableKitTests",
             dependencies: ["DynamicCodableKit"],
             resources: [
-                .process("JSONs"),
+                .process("DynamicDecodingContextCodingKey/JSONs"),
             ]
         ),
     ],

Tests/DynamicCodableKitTests/DynamicDecodable.swift

@@ -1,7 +1,39 @@
 import XCTest
 @testable import DynamicCodableKit
 
+extension Int: DynamicDecodable {}
+
 final class DynamicDecodableTests: XCTestCase {
+    func testDefaultDownCasting() throws {
+        let value: Decodable = try 5.castAs(type: Decodable.self, codingPath: [])
+        XCTAssertEqual(value as? Int, 5)
+    }
+    func testDefaultDownCastingFailure() throws {
+        XCTAssertThrowsError(try 5.castAs(type: String.self, codingPath: []))
+    }
+    func testDefaultOptionalDownCasting() throws {
+        let value: Decodable? = 5.castAs(type: Decodable?.self, codingPath: [])
+        XCTAssertEqual(value as? Int, 5)
+    }
+    func testDefaultOptionalDownCastingFailure() throws {
+        let value: String? = 5.castAs(type: String?.self, codingPath: [])
+        XCTAssertNil(value)
+    }
+    func testDefaultCollectionDownCasting() throws {
+        let value: [Decodable] = try [5, 6, 7].castAs(type: [Decodable].self, codingPath: [])
+        XCTAssertEqual(value as! Array<Int>, [5, 6, 7])
+        let set: Set<AnyHashable> = try ([5, 6, 7] as Set).castAs(type: Set<AnyHashable>.self, codingPath: [])
+        XCTAssertEqual(set, [5, 6, 7] as Set)
+    }
+    func testDefaultCollectionCastingForSingleValue() throws {
+        let value: [Decodable] = try 5.castAs(type: [Decodable].self, codingPath: [])
+        XCTAssertEqual(value as! Array<Int>, [5])
+        let set: Set<AnyHashable> = try 5.castAs(type: Set<AnyHashable>.self, codingPath: [])
+        XCTAssertEqual(set, [5] as Set)
+    }
+    func testDefaultCollectionDownCastingFailure() throws {
+        XCTAssertThrowsError(try [5, 6, 7].castAs(type: [String].self, codingPath: []))
+    }
     func testCastingToExistential() throws {
         let textPost = TextPost(
             id: UUID(),