diff --git a/main_test.go b/main_test.go
new file mode 100644
index 0000000..e282404
--- /dev/null
+++ b/main_test.go
@@ -0,0 +1,75 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestLoadConfig(t *testing.T) {
+	t.Run("it loads config", func(t *testing.T) {
+		path := path.Join(t.TempDir(), "config.json")
+
+		file, err := os.Create(path)
+		require.NoError(t, err, "failed to create temp file")
+		defer file.Close()
+
+		config := Config{
+			BaseURL:    "https://example.com",
+			Token:      "token",
+			UserID:     42,
+			ProjectIDs: []int{43, 44},
+		}
+
+		err = json.NewEncoder(file).Encode(config)
+		require.NoError(t, err, "failed to write to temp file")
+
+		loadedConfig, err := loadConfig(path)
+		require.NoError(t, err)
+		require.Equal(t, config, loadedConfig)
+	})
+}
+
+func TestLoadState(t *testing.T) {
+	t.Run("it loads state", func(t *testing.T) {
+		path := path.Join(t.TempDir(), "state.json")
+
+		file, err := os.Create(path)
+		require.NoError(t, err, "failed to create temp file")
+		defer file.Close()
+
+		state := NewState()
+		state.AddNote(MergeRequest{}, Note{})
+
+		err = json.NewEncoder(file).Encode(state)
+		require.NoError(t, err, "failed to write to temp file")
+
+		loadedState, err := loadState(path)
+		require.NoError(t, err)
+		require.Equal(t, state, loadedState)
+	})
+}
+
+func TestSaveState(t *testing.T) {
+	t.Run("it saves state", func(t *testing.T) {
+		path := path.Join(t.TempDir(), "state.json")
+
+		state := NewState()
+		state.AddNote(MergeRequest{}, Note{})
+
+		err := saveState(path, state)
+		require.NoError(t, err)
+
+		file, err := os.Open(path)
+		require.NoError(t, err)
+		defer file.Close()
+
+		savedState := NewState()
+		err = json.NewDecoder(file).Decode(&savedState)
+		require.NoError(t, err)
+		require.Equal(t, state, savedState)
+	})
+}