diff --git a/monitor/map.go b/monitor/map.go
index 4404b1d..f50a7e5 100644
--- a/monitor/map.go
+++ b/monitor/map.go
@@ -1,7 +1,10 @@
 package monitor
 
 import (
+	"fmt"
 	"io/ioutil"
+	"os"
+	"path/filepath"
 	"predictor/env"
 	"predictor/log"
 	"predictor/predictions"
@@ -11,13 +14,19 @@ import (
 	geojson "github.com/paulmach/go.geojson"
 )
 
+// Interface to overwrite for testing purposes.
+var getAllThings = things.Things.Range
+
+// Interface to overwrite for testing purposes.
+var getCurrentPrediction = predictions.GetCurrentPrediction
+
 // Write geojson data that can be used to visualize the predictions.
 // The geojson file is written to the static directory.
 func WriteGeoJSONMap() {
 	// Write the geojson to the file.
 	locationFeatureCollection := geojson.NewFeatureCollection() // Locations of traffic lights.
 	laneFeatureCollection := geojson.NewFeatureCollection()     // Lanes of traffic lights.
-	things.Things.Range(func(key, value interface{}) bool {
+	getAllThings(func(key, value interface{}) bool {
 		thingName := key.(string)
 		thing := value.(things.Thing)
 
@@ -30,7 +39,7 @@ func WriteGeoJSONMap() {
 		lat, lng := coordinate[1], coordinate[0]
 
 		// Check if there is a prediction for this thing.
-		prediction, predictionOk := predictions.GetCurrentPrediction(thingName)
+		prediction, predictionOk := getCurrentPrediction(thingName)
 		// Build the properties.
 		properties := make(map[string]interface{})
 		if predictionOk {
@@ -62,19 +71,33 @@ func WriteGeoJSONMap() {
 		return true
 	})
 
+	// Make sure the directory exists, otherwise create it.
+	locationsFilePath := fmt.Sprintf("%s/status/predictions-locations.geojson", env.StaticPath)
+	err := os.MkdirAll(filepath.Dir(locationsFilePath), os.ModePerm)
+	if err != nil {
+		log.Error.Println("Error creating dirs for geojson:", err)
+		return
+	}
 	locationsGeoJson, err := locationFeatureCollection.MarshalJSON()
 	if err != nil {
 		log.Error.Println("Error marshalling geojson:", err)
 		return
 	}
-	ioutil.WriteFile(env.StaticPath+"/status/predictions-locations.geojson", locationsGeoJson, 0644)
+	ioutil.WriteFile(locationsFilePath, locationsGeoJson, 0644)
 
+	// Make sure the directory exists, otherwise create it.
+	lanesFilePath := fmt.Sprintf("%s/status/predictions-lanes.geojson", env.StaticPath)
+	err = os.MkdirAll(filepath.Dir(lanesFilePath), os.ModePerm)
+	if err != nil {
+		log.Error.Println("Error creating dirs for geojson:", err)
+		return
+	}
 	lanesGeoJson, err := laneFeatureCollection.MarshalJSON()
 	if err != nil {
 		log.Error.Println("Error marshalling geojson:", err)
 		return
 	}
-	ioutil.WriteFile(env.StaticPath+"/status/predictions-lanes.geojson", lanesGeoJson, 0644)
+	ioutil.WriteFile(lanesFilePath, lanesGeoJson, 0644)
 }
 
 func UpdateGeoJSONMapPeriodically() {
diff --git a/monitor/map_test.go b/monitor/map_test.go
new file mode 100644
index 0000000..899b7c4
--- /dev/null
+++ b/monitor/map_test.go
@@ -0,0 +1,138 @@
+package monitor
+
+import (
+	"fmt"
+	"os"
+	"predictor/env"
+	"predictor/predictions"
+	"predictor/things"
+	"testing"
+	"time"
+
+	geojson "github.com/paulmach/go.geojson"
+)
+
+func TestWriteGeoJSONMap(t *testing.T) {
+	laneTopology := things.LocationMultiLineString{
+		Type: "MultiLineString",
+		// Mock values
+		Coordinates: [][][]float64{
+			// Ingress lane
+			{
+				{
+					0, 0,
+				},
+				{
+					1, 0,
+				},
+			},
+			// Connection lane
+			{
+				{
+					1, 0,
+				},
+				{
+					2, 0,
+				},
+			},
+			// Egress lane
+			{
+				{
+					2, 0,
+				},
+				{
+					3, 0,
+				},
+			},
+		},
+	}
+	getAllThings = func(callback func(key, value interface{}) bool) {
+		callback(
+			"1337_1", things.Thing{
+				Name: "1337_1",
+				Properties: things.ThingProperties{
+					LaneType: "Radfahrer",
+				},
+				Locations: []things.Location{
+					{
+						Location: things.LocationGeoJson{
+							Geometry: laneTopology,
+						},
+					},
+				},
+			},
+		)
+	}
+	mockPrediction := predictions.Prediction{
+		ThingName:     "1337_1",
+		Now:           []byte{1, 1, 1, 1, 1, 3, 3, 3, 3, 3},
+		NowQuality:    []byte{100, 100, 100, 100, 100, 100, 100, 100, 100, 100},
+		Then:          []byte{1, 1, 1, 1, 1, 3, 3, 3, 3, 3},
+		ThenQuality:   []byte{100, 100, 100, 100, 100, 100, 100, 100, 100, 100},
+		ReferenceTime: time.Unix(0, 0),
+	}
+	getCurrentPrediction = func(thingName string) (predictions.Prediction, bool) {
+		return mockPrediction, true
+	}
+
+	tempDir := t.TempDir()
+	env.StaticPath = tempDir
+
+	locationsGeoJSONFilePath := fmt.Sprintf("%s/status/predictions-locations.geojson", tempDir)
+	lanesGeoJSONFilePath := fmt.Sprintf("%s/status/predictions-lanes.geojson", tempDir)
+
+	WriteGeoJSONMap()
+
+	locationsData, err := os.ReadFile(locationsGeoJSONFilePath)
+	if err != nil {
+		t.Errorf("failed to read locations geojson file")
+		t.FailNow()
+	}
+	lanesData, err := os.ReadFile(lanesGeoJSONFilePath)
+	if err != nil {
+		t.Errorf("failed to read lanes geojson file")
+		t.FailNow()
+	}
+	locationsGeoJSON, err := geojson.UnmarshalFeatureCollection(locationsData)
+	if err != nil {
+		t.Errorf("failed to unmarshal geojson feature collection")
+		t.FailNow()
+	}
+	lanesGeoJSON, err := geojson.UnmarshalFeatureCollection(lanesData)
+	if err != nil {
+		t.Errorf("failed to unmarshal geojson feature collection")
+	}
+	if len(locationsGeoJSON.Features) != 1 || len(lanesGeoJSON.Features) != 1 {
+		t.Errorf("more or less than one geojson feature detected")
+		t.FailNow()
+	}
+	unmarshaledLocationFeature := locationsGeoJSON.Features[0]
+	unmarshaledLaneFeature := lanesGeoJSON.Features[0]
+
+	type checker func(v interface{}) bool
+	propertyChecks := map[string]checker{
+		"prediction_available": func(v interface{}) bool {
+			return v.(bool) == true
+		},
+		"prediction_quality": func(v interface{}) bool {
+			return v.(float64) == 1.0
+		},
+		"prediction_time_diff": func(v interface{}) bool {
+			return v.(float64) > 0
+		},
+		"prediction_sg_id": func(v interface{}) bool {
+			return v.(string) == "1337_1"
+		},
+	}
+
+	for key, check := range propertyChecks {
+		v := unmarshaledLocationFeature.Properties[key]
+		if !check(v) {
+			t.Errorf("property check failed: %v", v)
+		}
+		v = unmarshaledLaneFeature.Properties[key]
+		if !check(v) {
+			t.Errorf("property check failed: %v", v)
+		}
+	}
+}
diff --git a/things/location.go b/things/location.go
index c127429..a48dfa7 100644
--- a/things/location.go
+++ b/things/location.go
@@ -2,16 +2,20 @@ package things
 
 // A location model from the SensorThings API.
 type Location struct {
-	Description  string   `json:"description"`
-	EncodingType string   `json:"encodingType"`
-	IotId        int      `json:"@iot.id"`
-	Location     struct { // GeoJSON
-		Type     string `json:"type"`
-		Geometry struct {
-			Type        string        `json:"type"` // MultiLineString
-			Coordinates [][][]float64 `json:"coordinates"`
-		} `json:"geometry"`
-		Name     string `json:"name"`
-		SelfLink string `json:"@iot.selfLink"`
-	} `json:"location"`
+	Description  string          `json:"description"`
+	EncodingType string          `json:"encodingType"`
+	IotId        int             `json:"@iot.id"`
+	Location     LocationGeoJson `json:"location"`
+}
+
+type LocationGeoJson struct {
+	Type     string                  `json:"type"`
+	Geometry LocationMultiLineString `json:"geometry"`
+	Name     string                  `json:"name"`
+	SelfLink string                  `json:"@iot.selfLink"`
+}
+
+type LocationMultiLineString struct {
+	Type        string        `json:"type"` // MultiLineString
+	Coordinates [][][]float64 `json:"coordinates"`
 }
diff --git a/things/thing.go b/things/thing.go
index 10a5cac..8cbcd11 100644
--- a/things/thing.go
+++ b/things/thing.go
@@ -4,15 +4,17 @@ import "fmt"
 
 // A traffic light thing from the SensorThings API.
 type Thing struct {
-	IotId       int    `json:"@iot.id"`
-	Name        string `json:"name"`
-	Description string `json:"description"`
-	Properties  struct {
-		LaneType        string `json:"laneType"`
-		TrafficLightsId string `json:"trafficLightsId"` // This is the crossing.
-	} `json:"properties"`
-	Datastreams []Datastream `json:"Datastreams"`
-	Locations   []Location   `json:"Locations"`
+	IotId       int             `json:"@iot.id"`
+	Name        string          `json:"name"`
+	Description string          `json:"description"`
+	Properties  ThingProperties `json:"properties"`
+	Datastreams []Datastream    `json:"Datastreams"`
+	Locations   []Location      `json:"Locations"`
+}
+
+type ThingProperties struct {
+	LaneType        string `json:"laneType"`
+	TrafficLightsId string `json:"trafficLightsId"` // This is the crossing.
 }
 
 // Get the lane of a thing. This is the connection lane of the thing.