diff --git a/README.md b/README.md
index c010ffc..0178fa8 100644
--- a/README.md
+++ b/README.md
@@ -29,7 +29,7 @@ targets: [
 
 - Supports the full [GeoJSON standard][6], with some exceptions (see [TODO.md][7])
 - Load and write GeoJSON objects from and to `[String:Any]`, `URL`, `Data` and `String`
-- Supports `Codable`
+- Supports `Codable` and `SwiftData` (see below)
 - Supports EPSG:3857 (web mercator) and EPSG:4326 (geodetic) conversions
 - Supports WKT/WKB, also with different projections
 - Spatial search with a R-tree
@@ -655,6 +655,24 @@ func projected(to newProjection: Projection) -> FeatureCollection
 
 This type is somewhat special since its initializers will accept any valid GeoJSON object and return a `FeatureCollection` with the input wrapped in `Feature` objects if the input are geometries, or by collecting the input if it’s a `Feature`.
 
+# SwiftData
+
+You need to use a transformer for using GeoJson with SwiftData (also have a look at the [SwiftData test cases](https://github.com/Outdooractive/gis-tools/blob/main/Tests/GISToolsTests/GeoJson/SwiftDataTests.swift)).
+
+First, register the transformer like this:
+```swift
+GeoJsonTransformer.register()
+```
+
+Then create your models like this:
+```swift
+@Attribute(.transformable(by: GeoJsonTransformer.name.rawValue)) var geoJson: GeoJson?
+@Attribute(.transformable(by: GeoJsonTransformer.name.rawValue)) var point: Point?
+...
+```
+
+This is necessary because SwiftData doesn't work well with the default Codable implementation, so you need to do the serialization for yourself...
+
 # WKB/WKT
 The following geometry types are supported: `point`, `linestring`, `linearring`, `polygon`, `multipoint`, `multilinestring`, `multipolygon`, `geometrycollection` and `triangle`. Please open an issue if you need more.
 
diff --git a/Sources/GISTools/GeoJson/GeoJsonCodable.swift b/Sources/GISTools/GeoJson/GeoJsonCodable.swift
index a4c979e..e22f1e8 100644
--- a/Sources/GISTools/GeoJson/GeoJsonCodable.swift
+++ b/Sources/GISTools/GeoJson/GeoJsonCodable.swift
@@ -89,6 +89,44 @@ extension Coordinate3D: Codable {
 
 }
 
+// MARK: - SwiftData compatibility (see the README)
+
+#if canImport(SwiftData)
+@objc(GeoJsonTransformer)
+public final class GeoJsonTransformer: ValueTransformer {
+
+    public static let name = NSValueTransformerName(rawValue: "GeoJsonTransformer")
+
+    public static func register() {
+        ValueTransformer.setValueTransformer(GeoJsonTransformer(), forName: name)
+    }
+
+    public override class func transformedValueClass() -> AnyClass {
+        // returns __SwiftValue
+        type(of: Point(Coordinate3D.zero) as AnyObject)
+    }
+
+    public override class func allowsReverseTransformation() -> Bool {
+        true
+    }
+
+    // Encode GeoJSON to Data
+    public override func transformedValue(_ value: Any?) -> Any? {
+        guard let geoJson = value as? GeoJson else { return nil }
+
+        return geoJson.asJsonData()
+    }
+
+    // Decode Data to GeoJSON
+    public override func reverseTransformedValue(_ value: Any?) -> Any? {
+        guard let data = value as? Data else { return nil }
+
+        return GeoJsonReader.geoJsonFrom(jsonData: data)
+    }
+
+}
+#endif
+
 // MARK: - Private
 
 private struct GeoJsonCodingKey: CodingKey {
diff --git a/Tests/GISToolsTests/GeoJson/FeatureCollectionTests.swift b/Tests/GISToolsTests/GeoJson/FeatureCollectionTests.swift
index b7f3721..be7fd96 100644
--- a/Tests/GISToolsTests/GeoJson/FeatureCollectionTests.swift
+++ b/Tests/GISToolsTests/GeoJson/FeatureCollectionTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class FeatureCollectionTests: XCTestCase {
 
-    private let featureCollectionJson = """
+    static let featureCollectionJson = """
     {
         "type": "FeatureCollection",
         "features": [{
@@ -56,7 +56,7 @@ final class FeatureCollectionTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let featureCollection = try XCTUnwrap(FeatureCollection(jsonString: featureCollectionJson))
+        let featureCollection = try XCTUnwrap(FeatureCollection(jsonString: FeatureCollectionTests.featureCollectionJson))
 
         XCTAssertEqual(featureCollection.type, GeoJsonType.featureCollection)
         XCTAssertEqual(featureCollection.projection, .epsg4326)
@@ -94,7 +94,7 @@ final class FeatureCollectionTests: XCTestCase {
     }
 
     func testMap() throws {
-        var featureCollection = try XCTUnwrap(FeatureCollection(jsonString: featureCollectionJson))
+        var featureCollection = try XCTUnwrap(FeatureCollection(jsonString: FeatureCollectionTests.featureCollectionJson))
 
         let prop0: String? = featureCollection.features.first?.property(for: "prop0")
         XCTAssertEqual(prop0, "value0")
@@ -110,7 +110,7 @@ final class FeatureCollectionTests: XCTestCase {
     }
 
     func testCompactMap() throws {
-        var featureCollection = try XCTUnwrap(FeatureCollection(jsonString: featureCollectionJson))
+        var featureCollection = try XCTUnwrap(FeatureCollection(jsonString: FeatureCollectionTests.featureCollectionJson))
 
         XCTAssertEqual(featureCollection.features.count, 3)
 
@@ -123,7 +123,7 @@ final class FeatureCollectionTests: XCTestCase {
     }
 
     func testFilter() throws {
-        var featureCollection = try XCTUnwrap(FeatureCollection(jsonString: featureCollectionJson))
+        var featureCollection = try XCTUnwrap(FeatureCollection(jsonString: FeatureCollectionTests.featureCollectionJson))
 
         XCTAssertEqual(featureCollection.features.count, 3)
 
@@ -135,7 +135,7 @@ final class FeatureCollectionTests: XCTestCase {
     }
 
     func testEnumerate() throws {
-        let featureCollection = try XCTUnwrap(FeatureCollection(jsonString: featureCollectionJson))
+        let featureCollection = try XCTUnwrap(FeatureCollection(jsonString: FeatureCollectionTests.featureCollectionJson))
 
         let expected: [(Int, Int, Coordinate3D)] = [
             (0, 0, Coordinate3D(latitude: 0.5, longitude: 102.0)),
@@ -165,7 +165,7 @@ final class FeatureCollectionTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let featureCollection = try XCTUnwrap(FeatureCollection(jsonString: featureCollectionJson))
+        let featureCollection = try XCTUnwrap(FeatureCollection(jsonString: FeatureCollectionTests.featureCollectionJson))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -174,7 +174,7 @@ final class FeatureCollectionTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let featureCollectionData = try XCTUnwrap(FeatureCollection(jsonString: featureCollectionJson)?.asJsonData(prettyPrinted: true))
+        let featureCollectionData = try XCTUnwrap(FeatureCollection(jsonString: FeatureCollectionTests.featureCollectionJson)?.asJsonData(prettyPrinted: true))
         let featureCollection = try JSONDecoder().decode(FeatureCollection.self, from: featureCollectionData)
 
         XCTAssertEqual(featureCollection.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/FeatureTests.swift b/Tests/GISToolsTests/GeoJson/FeatureTests.swift
index 7f51af6..05c39c6 100644
--- a/Tests/GISToolsTests/GeoJson/FeatureTests.swift
+++ b/Tests/GISToolsTests/GeoJson/FeatureTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class FeatureTests: XCTestCase {
 
-    private let featureJson = """
+    static let featureJson = """
     {
        "type": "Feature",
        "geometry": {
@@ -30,7 +30,7 @@ final class FeatureTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let feature = try XCTUnwrap(Feature(jsonString: featureJson))
+        let feature = try XCTUnwrap(Feature(jsonString: FeatureTests.featureJson))
 
         XCTAssertEqual(feature.type, GeoJsonType.feature)
         XCTAssertEqual(feature.projection, .epsg4326)
@@ -44,7 +44,7 @@ final class FeatureTests: XCTestCase {
         XCTAssertEqual(feature.id, .string("abcd.1234"))
     }
 
-    private let featureJsonWithIntId = """
+    static let featureJsonWithIntId = """
     {
        "type": "Feature",
        "geometry": {
@@ -71,7 +71,7 @@ final class FeatureTests: XCTestCase {
     """
 
     func testLoadJsonWithIntId() throws {
-        let feature = try XCTUnwrap(Feature(jsonString: featureJsonWithIntId))
+        let feature = try XCTUnwrap(Feature(jsonString: FeatureTests.featureJsonWithIntId))
 
         XCTAssertEqual(feature.id, .int(1234))
         XCTAssertEqual(feature.projection, .epsg4326)
@@ -89,7 +89,7 @@ final class FeatureTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let feature = try XCTUnwrap(Feature(jsonString: featureJson))
+        let feature = try XCTUnwrap(Feature(jsonString: FeatureTests.featureJson))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -98,7 +98,7 @@ final class FeatureTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let featureData = try XCTUnwrap(Feature(jsonString: featureJson)?.asJsonData(prettyPrinted: true))
+        let featureData = try XCTUnwrap(Feature(jsonString: FeatureTests.featureJson)?.asJsonData(prettyPrinted: true))
         let feature = try JSONDecoder().decode(Feature.self, from: featureData)
 
         XCTAssertEqual(feature.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/GeometryCollectionTests.swift b/Tests/GISToolsTests/GeoJson/GeometryCollectionTests.swift
index a16547c..e738c13 100644
--- a/Tests/GISToolsTests/GeoJson/GeometryCollectionTests.swift
+++ b/Tests/GISToolsTests/GeoJson/GeometryCollectionTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class GeometryCollectionTests: XCTestCase {
 
-    private let geometryCollectionJson = """
+    static let geometryCollectionJson = """
     {
         "type": "GeometryCollection",
         "geometries": [{
@@ -21,7 +21,7 @@ final class GeometryCollectionTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let geometryCollection = try XCTUnwrap(GeometryCollection(jsonString: geometryCollectionJson))
+        let geometryCollection = try XCTUnwrap(GeometryCollection(jsonString: GeometryCollectionTests.geometryCollectionJson))
 
         XCTAssertNotNil(geometryCollection)
         XCTAssertEqual(geometryCollection.type, GeoJsonType.geometryCollection)
@@ -44,7 +44,7 @@ final class GeometryCollectionTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let geometryCollection = try XCTUnwrap(GeometryCollection(jsonString: geometryCollectionJson))
+        let geometryCollection = try XCTUnwrap(GeometryCollection(jsonString: GeometryCollectionTests.geometryCollectionJson))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -53,7 +53,7 @@ final class GeometryCollectionTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let geometryCollectionData = try XCTUnwrap(GeometryCollection(jsonString: geometryCollectionJson)?.asJsonData(prettyPrinted: true))
+        let geometryCollectionData = try XCTUnwrap(GeometryCollection(jsonString: GeometryCollectionTests.geometryCollectionJson)?.asJsonData(prettyPrinted: true))
         let geometryCollection = try JSONDecoder().decode(GeometryCollection.self, from: geometryCollectionData)
 
         XCTAssertEqual(geometryCollection.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/LineStringTests.swift b/Tests/GISToolsTests/GeoJson/LineStringTests.swift
index 4d5b17f..260259a 100644
--- a/Tests/GISToolsTests/GeoJson/LineStringTests.swift
+++ b/Tests/GISToolsTests/GeoJson/LineStringTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class LineStringTests: XCTestCase {
 
-    private let lineStringJson = """
+    static let lineStringJson = """
     {
         "type": "LineString",
         "coordinates": [
@@ -15,7 +15,7 @@ final class LineStringTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let lineString = try XCTUnwrap(LineString(jsonString: lineStringJson))
+        let lineString = try XCTUnwrap(LineString(jsonString: LineStringTests.lineStringJson))
 
         XCTAssertEqual(lineString.type, GeoJsonType.lineString)
         XCTAssertEqual(lineString.projection, .epsg4326)
@@ -52,7 +52,7 @@ final class LineStringTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let lineString = try XCTUnwrap(LineString(jsonString: lineStringJson))
+        let lineString = try XCTUnwrap(LineString(jsonString: LineStringTests.lineStringJson))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -61,7 +61,7 @@ final class LineStringTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let lineStringData = try XCTUnwrap(LineString(jsonString: lineStringJson)?.asJsonData(prettyPrinted: true))
+        let lineStringData = try XCTUnwrap(LineString(jsonString: LineStringTests.lineStringJson)?.asJsonData(prettyPrinted: true))
         let lineString = try JSONDecoder().decode(LineString.self, from: lineStringData)
 
         XCTAssertEqual(lineString.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/MultiLineStringTests.swift b/Tests/GISToolsTests/GeoJson/MultiLineStringTests.swift
index b2efb2d..2189b76 100644
--- a/Tests/GISToolsTests/GeoJson/MultiLineStringTests.swift
+++ b/Tests/GISToolsTests/GeoJson/MultiLineStringTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class MultiLineStringTests: XCTestCase {
 
-    private let multiLineStringJson = """
+    static let multiLineStringJson = """
     {
         "type": "MultiLineString",
         "coordinates": [
@@ -21,7 +21,7 @@ final class MultiLineStringTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let multiLineString = try XCTUnwrap(MultiLineString(jsonString: multiLineStringJson))
+        let multiLineString = try XCTUnwrap(MultiLineString(jsonString: MultiLineStringTests.multiLineStringJson))
 
         XCTAssertNotNil(multiLineString)
         XCTAssertEqual(multiLineString.type, GeoJsonType.multiLineString)
@@ -50,7 +50,7 @@ final class MultiLineStringTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let multiLineString = try XCTUnwrap(MultiLineString(jsonString: multiLineStringJson))
+        let multiLineString = try XCTUnwrap(MultiLineString(jsonString: MultiLineStringTests.multiLineStringJson))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -59,7 +59,7 @@ final class MultiLineStringTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let multiLineStringData = try XCTUnwrap(MultiLineString(jsonString: multiLineStringJson)?.asJsonData(prettyPrinted: true))
+        let multiLineStringData = try XCTUnwrap(MultiLineString(jsonString: MultiLineStringTests.multiLineStringJson)?.asJsonData(prettyPrinted: true))
         let multiLineString = try JSONDecoder().decode(MultiLineString.self, from: multiLineStringData)
 
         XCTAssertEqual(multiLineString.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/MultiPointTests.swift b/Tests/GISToolsTests/GeoJson/MultiPointTests.swift
index 4dc0ef1..7e83220 100644
--- a/Tests/GISToolsTests/GeoJson/MultiPointTests.swift
+++ b/Tests/GISToolsTests/GeoJson/MultiPointTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class MultiPointTests: XCTestCase {
 
-    private let multiPointJson = """
+    static let multiPointJson = """
     {
         "type": "MultiPoint",
         "coordinates": [
@@ -15,7 +15,7 @@ final class MultiPointTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let multiPoint = try XCTUnwrap(MultiPoint(jsonString: multiPointJson))
+        let multiPoint = try XCTUnwrap(MultiPoint(jsonString: MultiPointTests.multiPointJson))
 
         XCTAssertNotNil(multiPoint)
         XCTAssertEqual(multiPoint.type, GeoJsonType.multiPoint)
@@ -35,7 +35,7 @@ final class MultiPointTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let multiPoint = try XCTUnwrap(MultiPoint(jsonString: multiPointJson))
+        let multiPoint = try XCTUnwrap(MultiPoint(jsonString: MultiPointTests.multiPointJson))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -44,7 +44,7 @@ final class MultiPointTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let multiPointData = try XCTUnwrap(MultiPoint(jsonString: multiPointJson)?.asJsonData(prettyPrinted: true))
+        let multiPointData = try XCTUnwrap(MultiPoint(jsonString: MultiPointTests.multiPointJson)?.asJsonData(prettyPrinted: true))
         let multiPoint = try JSONDecoder().decode(MultiPoint.self, from: multiPointData)
 
         XCTAssertEqual(multiPoint.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/MultiPolygonTests.swift b/Tests/GISToolsTests/GeoJson/MultiPolygonTests.swift
index 59b7693..ab8366c 100644
--- a/Tests/GISToolsTests/GeoJson/MultiPolygonTests.swift
+++ b/Tests/GISToolsTests/GeoJson/MultiPolygonTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class MultiPolygonTests: XCTestCase {
 
-    private let multiPolygonJson = """
+    static let multiPolygonJson = """
     {
         "type": "MultiPolygon",
         "coordinates": [
@@ -38,7 +38,7 @@ final class MultiPolygonTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let multiPolygon = try XCTUnwrap(MultiPolygon(jsonString: multiPolygonJson))
+        let multiPolygon = try XCTUnwrap(MultiPolygon(jsonString: MultiPolygonTests.multiPolygonJson))
 
         XCTAssertEqual(multiPolygon.type, GeoJsonType.multiPolygon)
         XCTAssertEqual(multiPolygon.projection, .epsg4326)
@@ -57,7 +57,7 @@ final class MultiPolygonTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let multiPolygon = try XCTUnwrap(MultiPolygon(jsonString: multiPolygonJson))
+        let multiPolygon = try XCTUnwrap(MultiPolygon(jsonString: MultiPolygonTests.multiPolygonJson))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -66,7 +66,7 @@ final class MultiPolygonTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let multiPolygonData = try XCTUnwrap(MultiPolygon(jsonString: multiPolygonJson)?.asJsonData(prettyPrinted: true))
+        let multiPolygonData = try XCTUnwrap(MultiPolygon(jsonString: MultiPolygonTests.multiPolygonJson)?.asJsonData(prettyPrinted: true))
         let multiPolygon = try JSONDecoder().decode(MultiPolygon.self, from: multiPolygonData)
 
         XCTAssertEqual(multiPolygon.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/PointTests.swift b/Tests/GISToolsTests/GeoJson/PointTests.swift
index c82052b..7885f59 100644
--- a/Tests/GISToolsTests/GeoJson/PointTests.swift
+++ b/Tests/GISToolsTests/GeoJson/PointTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class PointTests: XCTestCase {
 
-    private let pointJson = """
+    static let pointJson = """
     {
         "type": "Point",
         "coordinates": [100.0, 0.0],
@@ -12,7 +12,7 @@ final class PointTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let point =  try XCTUnwrap(Point(jsonString: pointJson))
+        let point = try XCTUnwrap(Point(jsonString: PointTests.pointJson))
 
         XCTAssertEqual(point.type, GeoJsonType.point)
         XCTAssertEqual(point.projection, .epsg4326)
@@ -31,7 +31,7 @@ final class PointTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let point = try XCTUnwrap(Point(jsonString: pointJson))
+        let point = try XCTUnwrap(Point(jsonString: PointTests.pointJson))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -40,7 +40,7 @@ final class PointTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let pointData = try XCTUnwrap(Point(jsonString: pointJson)?.asJsonData(prettyPrinted: true))
+        let pointData = try XCTUnwrap(Point(jsonString: PointTests.pointJson)?.asJsonData(prettyPrinted: true))
         let point = try JSONDecoder().decode(Point.self, from: pointData)
 
         XCTAssertEqual(point.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/PolygonTests.swift b/Tests/GISToolsTests/GeoJson/PolygonTests.swift
index b0c1384..58be6b9 100644
--- a/Tests/GISToolsTests/GeoJson/PolygonTests.swift
+++ b/Tests/GISToolsTests/GeoJson/PolygonTests.swift
@@ -3,7 +3,7 @@ import XCTest
 
 final class PolygonTests: XCTestCase {
 
-    private let polygonJsonNoHole = """
+    static let polygonJsonNoHole = """
     {
         "type": "Polygon",
         "coordinates": [
@@ -19,7 +19,7 @@ final class PolygonTests: XCTestCase {
     }
     """
 
-    let polygonJsonWithHoles = """
+    static let polygonJsonWithHoles = """
     {
         "type": "Polygon",
         "coordinates": [
@@ -43,7 +43,7 @@ final class PolygonTests: XCTestCase {
     """
 
     func testLoadJson() throws {
-        let polygonNoHole = try XCTUnwrap(Polygon(jsonString: polygonJsonNoHole))
+        let polygonNoHole = try XCTUnwrap(Polygon(jsonString: PolygonTests.polygonJsonNoHole))
 
         XCTAssertEqual(polygonNoHole.type, GeoJsonType.polygon)
         XCTAssertEqual(polygonNoHole.projection, .epsg4326)
@@ -51,7 +51,7 @@ final class PolygonTests: XCTestCase {
         XCTAssertEqual(polygonNoHole.foreignMember(for: "other"), "something else")
         XCTAssertEqual(polygonNoHole[foreignMember: "other"], "something else")
 
-        let polygonWithHoles = try XCTUnwrap(Polygon(jsonString: polygonJsonWithHoles))
+        let polygonWithHoles = try XCTUnwrap(Polygon(jsonString: PolygonTests.polygonJsonWithHoles))
 
         XCTAssertEqual(polygonWithHoles.type, GeoJsonType.polygon)
         XCTAssertEqual(polygonWithHoles.projection, .epsg4326)
@@ -79,8 +79,8 @@ final class PolygonTests: XCTestCase {
     }
 
     func testEncodable() throws {
-        let polygonNoHole = try XCTUnwrap(Polygon(jsonString: polygonJsonNoHole))
-        let polygonWithHoles = try XCTUnwrap(Polygon(jsonString: polygonJsonWithHoles))
+        let polygonNoHole = try XCTUnwrap(Polygon(jsonString: PolygonTests.polygonJsonNoHole))
+        let polygonWithHoles = try XCTUnwrap(Polygon(jsonString: PolygonTests.polygonJsonWithHoles))
 
         let encoder = JSONEncoder()
         encoder.outputFormatting = [.prettyPrinted, .sortedKeys]
@@ -90,10 +90,10 @@ final class PolygonTests: XCTestCase {
     }
 
     func testDecodable() throws {
-        let polygonNoHoleData = try XCTUnwrap(Polygon(jsonString: polygonJsonNoHole)?.asJsonData(prettyPrinted: true))
+        let polygonNoHoleData = try XCTUnwrap(Polygon(jsonString: PolygonTests.polygonJsonNoHole)?.asJsonData(prettyPrinted: true))
         let polygonNoHole = try JSONDecoder().decode(Polygon.self, from: polygonNoHoleData)
 
-        let polygonWithHolesData = try XCTUnwrap(Polygon(jsonString: polygonJsonWithHoles)?.asJsonData(prettyPrinted: true))
+        let polygonWithHolesData = try XCTUnwrap(Polygon(jsonString: PolygonTests.polygonJsonWithHoles)?.asJsonData(prettyPrinted: true))
         let polygonWithHoles = try JSONDecoder().decode(Polygon.self, from: polygonWithHolesData)
 
         XCTAssertEqual(polygonNoHole.projection, .epsg4326)
diff --git a/Tests/GISToolsTests/GeoJson/SwiftDataTests.swift b/Tests/GISToolsTests/GeoJson/SwiftDataTests.swift
new file mode 100644
index 0000000..62a9684
--- /dev/null
+++ b/Tests/GISToolsTests/GeoJson/SwiftDataTests.swift
@@ -0,0 +1,61 @@
+@testable import GISTools
+import XCTest
+
+#if canImport(SwiftData)
+import SwiftData
+
+@available(macOS 14, iOS 17, watchOS 10, tvOS 17, *)
+final class SwiftDataTests: XCTestCase {
+
+    @Model
+    class GeoJsonModel {
+        @Attribute(.unique) var id: Int
+        @Attribute(.transformable(by: GeoJsonTransformer.name.rawValue)) var geoJson: GeoJson?
+
+        init(id: Int, geoJson: GeoJson) {
+            self.id = id
+            self.geoJson = geoJson
+        }
+    }
+
+    let container = {
+        GeoJsonTransformer.register()
+
+        let config = ModelConfiguration(isStoredInMemoryOnly: true)
+        return try! ModelContainer(for: GeoJsonModel.self, configurations: config)
+    }()
+
+    @MainActor
+    func testInsert() throws {
+        let geoJsonTests: [Int: GeoJson] = [
+            0: try XCTUnwrap(Point(jsonString: PointTests.pointJson)),
+            1: try XCTUnwrap(MultiPoint(jsonString: MultiPointTests.multiPointJson)),
+            2: try XCTUnwrap(Feature(jsonString: FeatureTests.featureJson)),
+            3: try XCTUnwrap(FeatureCollection(jsonString: FeatureCollectionTests.featureCollectionJson)),
+            4: try XCTUnwrap(GeometryCollection(jsonString: GeometryCollectionTests.geometryCollectionJson)),
+            5: try XCTUnwrap(LineString(jsonString: LineStringTests.lineStringJson)),
+            6: try XCTUnwrap(MultiLineString(jsonString: MultiLineStringTests.multiLineStringJson)),
+            7: try XCTUnwrap(Polygon(jsonString: PolygonTests.polygonJsonNoHole)),
+            8: try XCTUnwrap(MultiPolygon(jsonString: MultiPolygonTests.multiPolygonJson)),
+        ]
+
+        // Insert
+        for (id, geoJson) in geoJsonTests {
+            let model = GeoJsonModel(id: id, geoJson: geoJson)
+            container.mainContext.insert(model)
+        }
+
+        // Check
+        for (id, geoJson) in geoJsonTests {
+            var descriptor = FetchDescriptor<GeoJsonModel>(
+                predicate: #Predicate { $0.id == id },
+                sortBy: [SortDescriptor(\.id)])
+            descriptor.fetchLimit = 1
+
+            let result = try XCTUnwrap(container.mainContext.fetch(descriptor).first?.geoJson)
+            XCTAssertTrue(result.isEqualTo(geoJson))
+        }
+    }
+
+}
+#endif