diff --git a/Sources/TypedDate/TypedDate+Codable.swift b/Sources/TypedDate/TypedDate+Codable.swift
new file mode 100644
index 0000000..917e373
--- /dev/null
+++ b/Sources/TypedDate/TypedDate+Codable.swift
@@ -0,0 +1,118 @@
+import Foundation
+
+extension TypedDate: Codable {
+    public init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let date = try container.decode(Date.self, forKey: .date)
+        let calendar = Calendar.current
+
+        switch Components.self {
+        case is (Year).Type:
+            let dc = calendar.dateComponents([.year], from: date)
+            guard let date = calendar.date(from: dc),
+                  let year = dc.year
+            else {
+                throw TypedDateDecodingError.invalidDate
+            }
+            self.date = date
+            self.components = Year(year) as! Components
+
+        case is (Year, Month).Type:
+            let dc = calendar.dateComponents([.year, .month], from: date)
+            guard let date = calendar.date(from: dc),
+                  let year = dc.year,
+                  let month = dc.month
+            else {
+                throw TypedDateDecodingError.invalidDate
+            }
+            self.date = date
+            self.components = (Year(year), Month(month)) as! Components
+
+        case is (Year, Month, Day).Type:
+            let dc = calendar.dateComponents([.year, .month, .day], from: date)
+            guard let date = calendar.date(from: dc),
+                  let year = dc.year,
+                  let month = dc.month,
+                  let day = dc.day
+            else {
+                throw TypedDateDecodingError.invalidDate
+            }
+            self.date = date
+            self.components = (Year(year), Month(month), Day(day)) as! Components
+
+        case is (Year, Month, Day, Hour).Type:
+            let dc = calendar.dateComponents([.year, .month, .day, .hour], from: date)
+            guard let date = calendar.date(from: dc),
+                  let year = dc.year,
+                  let month = dc.month,
+                  let day = dc.day,
+                  let hour = dc.hour
+            else {
+                throw TypedDateDecodingError.invalidDate
+            }
+            self.date = date
+            self.components = (Year(year), Month(month), Day(day), Hour(hour)) as! Components
+
+        case is (Year, Month, Day, Hour, Minute).Type:
+            let dc = calendar.dateComponents([.year, .month, .day, .hour, .minute], from: date)
+            guard let date = calendar.date(from: dc),
+                  let year = dc.year,
+                  let month = dc.month,
+                  let day = dc.day,
+                  let hour = dc.hour,
+                  let minute = dc.minute
+            else {
+                throw TypedDateDecodingError.invalidDate
+            }
+            self.date = date
+            self.components = (Year(year), Month(month), Day(day), Hour(hour), Minute(minute)) as! Components
+
+        case is (Year, Month, Day, Hour, Minute, Second).Type:
+            let dc = calendar.dateComponents([.year, .month, .day, .hour, .minute, .second], from: date)
+            guard let date = calendar.date(from: dc),
+                  let year = dc.year,
+                  let month = dc.month,
+                  let day = dc.day,
+                  let hour = dc.hour,
+                  let minute = dc.minute,
+                  let second = dc.second
+            else {
+                throw TypedDateDecodingError.invalidDate
+            }
+            self.date = date
+            self.components = (Year(year), Month(month), Day(day), Hour(hour), Minute(minute), Second(second)) as! Components
+
+        case is (Year, Month, Day, Hour, Minute, Second, Nanosecond).Type:
+            let dc = calendar.dateComponents([.year, .month, .day, .hour, .minute, .second, .nanosecond], from: date)
+            guard let date = calendar.date(from: dc),
+                  let year = dc.year,
+                  let month = dc.month,
+                  let day = dc.day,
+                  let hour = dc.hour,
+                  let minute = dc.minute,
+                  let second = dc.second
+            else {
+                throw TypedDateDecodingError.invalidDate
+            }
+            let nanosecond = dc.nanosecond ?? 0
+            self.date = date
+            self.components = (Year(year), Month(month), Day(day), Hour(hour), Minute(minute), Second(second), Nanosecond(nanosecond)) as! Components
+
+        default: throw TypedDateDecodingError.invalidComponents
+        }
+    }
+
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(date, forKey: .date)
+    }
+
+    public enum CodingKeys: CodingKey {
+        case date
+    }
+}
+
+public enum TypedDateDecodingError: Error {
+    case invalidDate
+    case invalidComponents
+}
diff --git a/Sources/TypedDate/TypedDate+fillIn.swift b/Sources/TypedDate/TypedDate+fill.swift
similarity index 100%
rename from Sources/TypedDate/TypedDate+fillIn.swift
rename to Sources/TypedDate/TypedDate+fill.swift
diff --git a/Sources/TypedDate/TypedDate.swift b/Sources/TypedDate/TypedDate.swift
index 29a800b..3e2c30f 100644
--- a/Sources/TypedDate/TypedDate.swift
+++ b/Sources/TypedDate/TypedDate.swift
@@ -5,119 +5,3 @@ public struct TypedDate<Components: Sendable>: Sendable {
 
     let components: Components
 }
-
-extension TypedDate: Codable {
-    public init(from decoder: Decoder) throws {
-        let container = try decoder.container(keyedBy: CodingKeys.self)
-        let date = try container.decode(Date.self, forKey: .date)
-        let calendar = Calendar.current
-
-        switch Components.self {
-        case is (Year).Type:
-            let dc = calendar.dateComponents([.year], from: date)
-            guard let date = calendar.date(from: dc),
-                  let year = dc.year
-            else {
-                throw TypedDateDecodingError.invalidDate
-            }
-            self.date = date
-            self.components = Year(year) as! Components
-
-        case is (Year, Month).Type:
-            let dc = calendar.dateComponents([.year, .month], from: date)
-            guard let date = calendar.date(from: dc),
-                  let year = dc.year,
-                  let month = dc.month
-            else {
-                throw TypedDateDecodingError.invalidDate
-            }
-            self.date = date
-            self.components = (Year(year), Month(month)) as! Components
-
-        case is (Year, Month, Day).Type:
-            let dc = calendar.dateComponents([.year, .month, .day], from: date)
-            guard let date = calendar.date(from: dc),
-                  let year = dc.year,
-                  let month = dc.month,
-                  let day = dc.day
-            else {
-                throw TypedDateDecodingError.invalidDate
-            }
-            self.date = date
-            self.components = (Year(year), Month(month), Day(day)) as! Components
-
-        case is (Year, Month, Day, Hour).Type:
-            let dc = calendar.dateComponents([.year, .month, .day, .hour], from: date)
-            guard let date = calendar.date(from: dc),
-                  let year = dc.year,
-                  let month = dc.month,
-                  let day = dc.day,
-                  let hour = dc.hour
-            else {
-                throw TypedDateDecodingError.invalidDate
-            }
-            self.date = date
-            self.components = (Year(year), Month(month), Day(day), Hour(hour)) as! Components
-
-        case is (Year, Month, Day, Hour, Minute).Type:
-            let dc = calendar.dateComponents([.year, .month, .day, .hour, .minute], from: date)
-            guard let date = calendar.date(from: dc),
-                  let year = dc.year,
-                  let month = dc.month,
-                  let day = dc.day,
-                  let hour = dc.hour,
-                  let minute = dc.minute
-            else {
-                throw TypedDateDecodingError.invalidDate
-            }
-            self.date = date
-            self.components = (Year(year), Month(month), Day(day), Hour(hour), Minute(minute)) as! Components
-
-        case is (Year, Month, Day, Hour, Minute, Second).Type:
-            let dc = calendar.dateComponents([.year, .month, .day, .hour, .minute, .second], from: date)
-            guard let date = calendar.date(from: dc),
-                  let year = dc.year,
-                  let month = dc.month,
-                  let day = dc.day,
-                  let hour = dc.hour,
-                  let minute = dc.minute,
-                  let second = dc.second
-            else {
-                throw TypedDateDecodingError.invalidDate
-            }
-            self.date = date
-            self.components = (Year(year), Month(month), Day(day), Hour(hour), Minute(minute), Second(second)) as! Components
-
-        case is (Year, Month, Day, Hour, Minute, Second, Nanosecond).Type:
-            let dc = calendar.dateComponents([.year, .month, .day, .hour, .minute, .second, .nanosecond], from: date)
-            guard let date = calendar.date(from: dc),
-                  let year = dc.year,
-                  let month = dc.month,
-                  let day = dc.day,
-                  let hour = dc.hour,
-                  let minute = dc.minute,
-                  let second = dc.second
-            else {
-                throw TypedDateDecodingError.invalidDate
-            }
-            let nanosecond = dc.nanosecond ?? 0
-            self.date = date
-            self.components = (Year(year), Month(month), Day(day), Hour(hour), Minute(minute), Second(second), Nanosecond(nanosecond)) as! Components
-
-        default: throw TypedDateDecodingError.invalidDate
-        }
-    }
-
-    public func encode(to encoder: Encoder) throws {
-        var container = encoder.container(keyedBy: CodingKeys.self)
-        try container.encode(date, forKey: .date)
-    }
-
-    public enum CodingKeys: CodingKey {
-        case date
-    }
-}
-
-public enum TypedDateDecodingError: Error {
-    case invalidDate
-}
diff --git a/Tests/TypedDateTests/TypedDateCodableTests.swift b/Tests/TypedDateTests/TypedDateCodableTests.swift
new file mode 100644
index 0000000..a8a0350
--- /dev/null
+++ b/Tests/TypedDateTests/TypedDateCodableTests.swift
@@ -0,0 +1,37 @@
+import Foundation
+import Testing
+@testable import TypedDate
+
+@Suite
+struct TypedDateCodableTests {
+    let calendar: Calendar
+    let testSupport: TypedDateTestSupport
+
+    init() {
+        calendar = Calendar(identifier: .gregorian)
+        testSupport = TypedDateTestSupport.init(calendar: calendar)
+    }
+
+    @Test
+    func testCodable() throws {
+        let typedDate = testSupport.generateTypedNanosecondDate()
+        let jsonEncoder = JSONEncoder()
+        let data = try jsonEncoder.encode(typedDate)
+        let decoded1 = try JSONDecoder().decode(TypedDate<(Year, Month, Day, Hour, Minute, Second, Nanosecond)>.self, from: data)
+        testSupport.assertTypedDate(for: decoded1)
+        let decoded2 = try JSONDecoder().decode(TypedDate<(Year, Month, Day, Hour, Minute, Second)>.self, from: data)
+        testSupport.assertTypedDate(for: decoded2)
+        let decoded3 = try JSONDecoder().decode(TypedDate<(Year, Month, Day, Hour, Minute)>.self, from: data)
+        testSupport.assertTypedDate(for: decoded3)
+        let decoded4 = try JSONDecoder().decode(TypedDate<(Year, Month, Day, Hour)>.self, from: data)
+        testSupport.assertTypedDate(for: decoded4)
+        let decoded5 = try JSONDecoder().decode(TypedDate<(Year, Month, Day)>.self, from: data)
+        testSupport.assertTypedDate(for: decoded5)
+        let decoded6 = try JSONDecoder().decode(TypedDate<(Year, Month)>.self, from: data)
+        testSupport.assertTypedDate(for: decoded6)
+        let decoded7 = try JSONDecoder().decode(TypedDate<(Year, Month)>.self, from: data)
+        testSupport.assertTypedDate(for: decoded7)
+        let decoded8 = try JSONDecoder().decode(TypedDate<(Year)>.self, from: data)
+        testSupport.assertTypedDate(for: decoded8)
+    }
+}