Use parser function from station package

app.go

@@ -1,15 +1,15 @@
 package main
 
 import (
-	"github.com/kacpermalachowski/marshal-controller/pkg/station"
-	"github.com/kacpermalachowski/marshal-controller/pkg/td2"
 	"context"
 	"crypto/sha256"
 	"fmt"
 	"os"
 
+	"github.com/kacpermalachowski/marshal-controller/pkg/station"
+	"github.com/kacpermalachowski/marshal-controller/pkg/td2"
+
 	"github.com/wailsapp/wails/v2/pkg/runtime"
-	"gopkg.in/yaml.v3"
 )
 
 type App struct {
@@ -50,8 +50,7 @@ func (a *App) LoadStationFile() station.Definition {
 		return a.station
 	}
 
-	var station station.Definition
-	err = yaml.Unmarshal(data, &station)
+	station, err := station.ParseStationDefinition(data)
 	if err != nil {
 		runtime.LogError(a.ctx, fmt.Sprint(err))
 		return a.station

pkg/station/station.go

@@ -1,5 +1,11 @@
 package station
 
+import (
+	"fmt"
+
+	"gopkg.in/yaml.v3"
+)
+
 type Definition struct {
 	Hills []Hill `json:"hills" yaml:"hills"`
 }
@@ -8,3 +14,17 @@ type Hill struct {
 	Signal    string   `json:"signal" yaml:"signal"`
 	Repeaters []string `json:"repeaters" yaml:"repeaters"`
 }
+
+func ParseStationDefinition(data []byte) (Definition, error) {
+	var station Definition
+	err := yaml.Unmarshal(data, &station)
+	if err != nil {
+		return Definition{}, err
+	}
+
+	if len(station.Hills) == 0 {
+		return Definition{}, fmt.Errorf("the program is unusable without hills defined")
+	}
+
+	return station, err
+}

pkg/station/station_test.go

@@ -0,0 +1,94 @@
+package station_test
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/kacpermalachowski/marshal-controller/pkg/station"
+)
+
+func TestParseStationDefinition(t *testing.T) {
+	tc := []struct {
+		Name      string
+		Data      string
+		Expected  station.Definition
+		ExpectErr bool
+	}{
+		{
+			Name:      "No hills",
+			Data:      `hills:`,
+			ExpectErr: true,
+		},
+		{
+			Name: "Single hill and signal",
+			Data: `hills:
+  - signal: Tr1`,
+			Expected: station.Definition{
+				Hills: []station.Hill{
+					{
+						Signal: "Tr1",
+					},
+				},
+			},
+		},
+		{
+			Name: "Single hill with repeaters",
+			Data: `hills:
+  - signal: Tr1
+    repeaters:
+      - Tr2`,
+			Expected: station.Definition{
+				Hills: []station.Hill{
+					{
+						Signal: "Tr1",
+						Repeaters: []string{
+							"Tr2",
+						},
+					},
+				},
+			},
+		},
+		{
+			Name: "Multiple hill with repeaters",
+			Data: `hills:
+  - signal: Tr1
+    repeaters:
+      - Tr2
+  - signal: Tr3
+    repeaters:
+      - Tr4`,
+			Expected: station.Definition{
+				Hills: []station.Hill{
+					{
+						Signal: "Tr1",
+						Repeaters: []string{
+							"Tr2",
+						},
+					},
+					{
+						Signal: "Tr3",
+						Repeaters: []string{
+							"Tr4",
+						},
+					},
+				},
+			},
+		},
+	}
+
+	for _, c := range tc {
+		t.Run(c.Name, func(t *testing.T) {
+			def, err := station.ParseStationDefinition([]byte(c.Data))
+			if err != nil && !c.ExpectErr {
+				t.Errorf("Unexpected error occured: %s", err)
+			}
+			if c.ExpectErr && err == nil {
+				t.Error("Expected error, but no one occured")
+			}
+
+			if !reflect.DeepEqual(c.Expected, def) {
+				t.Errorf("Expected %v, but got %v", c.Expected, def)
+			}
+		})
+	}
+}