Let it conform to `Codable`.

Sources/TimeSpecification/TimeSpecification.swift

@@ -58,6 +58,25 @@ public struct TimeSpecification {
   }
 }
 
+extension TimeSpecification: Codable {
+  public enum CodingKeys: String, CodingKey {
+    case seconds, nanoseconds
+  }
+  
+  public func encode(to encoder: Encoder) throws {
+    var container = encoder.container(keyedBy: CodingKeys.self)
+    try container.encode(self.seconds, forKey: .seconds)
+    try container.encode(self.nanoseconds, forKey: .nanoseconds)
+  }
+  
+  public init(from decoder: Decoder) throws {
+    let container = try decoder.container(keyedBy: CodingKeys.self)
+    let seconds = try container.decode(Int64.self, forKey: .seconds)
+    let nanoseconds = try container.decode(Int32.self, forKey: .nanoseconds)
+    self.init(seconds: seconds, nanoseconds: nanoseconds)
+  }
+}
+
 extension TimeSpecification: Equatable {
   public static func ==(lhs:TimeSpecification, rhs:TimeSpecification) -> Bool {
     return lhs.seconds == rhs.seconds && lhs.nanoseconds == rhs.nanoseconds

Tests/TimeSpecificationTests/TimeSpecificationTests.swift

@@ -8,6 +8,8 @@
 import XCTest
 @testable import TimeSpecification
 
+import Foundation
+
 class TimeSpecificationTests: XCTestCase {
   func test_normalization() {
     let N1 = TimeSpecification(seconds:0, nanoseconds:1_234_567_890)
@@ -17,6 +19,15 @@ class TimeSpecificationTests: XCTestCase {
     XCTAssertTrue(N2.seconds == -3 && N2.nanoseconds == 765_432_110, "Normalization Test 2")
   }
   
+  func test_codable() throws {
+    let spec = TimeSpecification(seconds: 123, nanoseconds: 456_789)
+    let encoded = try JSONEncoder().encode(spec)
+    XCTAssertEqual(String(data: encoded, encoding: .utf8), #"{"seconds":123,"nanoseconds":456789}"#)
+    
+    let decoded = try JSONDecoder().decode(TimeSpecification.self, from: encoded)
+    XCTAssertEqual(decoded, spec)
+  }
+  
   func test_comparison() {
     let C1 = TimeSpecification(seconds:100, nanoseconds:100)
     let C2 = TimeSpecification(seconds: 98, nanoseconds:2_000_000_100)

Tests/TimeSpecificationTests/XCTestManifests.swift

@@ -6,7 +6,10 @@ extension TimeSpecificationTests {
     //   `swift test --generate-linuxmain`
     // to regenerate.
     static let __allTests__TimeSpecificationTests = [
+        ("test_codable", test_codable),
         ("test_comparison", test_comparison),
+        ("test_date", test_date),
+        ("test_description", test_description),
         ("test_floatLiteral", test_floatLiteral),
         ("test_integerLiteral", test_integerLiteral),
         ("test_normalization", test_normalization),