1 files changed, 92 insertions, 0 deletions
diff --git a/kstore/store_test.go b/kstore/store_test.go
new file mode 100644
index 0000000..bbbd97a
--- /dev/null
+++ b/kstore/store_test.go
@@ -0,0 +1,92 @@
+package kstore
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type document struct {
+	Name  string `json:"name" yaml:"name"`
+	Count int    `json:"count" yaml:"count"`
+}
+
+func TestJSONRoundTrip(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "document.json")
+	want := document{Name: "example", Count: 3}
+
+	require.NoError(t, Save(path, want, JSON, 0o600))
+	got, err := Load[document](path, JSON)
+
+	require.NoError(t, err)
+	assert.Equal(t, want, got)
+}
+
+func TestYAMLRoundTrip(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "document.yaml")
+	want := document{Name: "example", Count: 3}
+
+	require.NoError(t, Save(path, want, YAML, 0o640))
+	got, err := Load[document](path, YAML)
+
+	require.NoError(t, err)
+	assert.Equal(t, want, got)
+}
+
+func TestLoadMalformedDocument(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "document.json")
+	require.NoError(t, os.WriteFile(path, []byte("not json"), 0o600))
+
+	_, err := Load[document](path, JSON)
+
+	assert.Error(t, err)
+}
+
+func TestLoadMissingDocument(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "missing.json")
+
+	_, err := Load[document](path, JSON)
+
+	assert.ErrorIs(t, err, os.ErrNotExist)
+}
+
+func TestSaveSetsRequestedPermissions(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "document.json")
+
+	require.NoError(t, Save(path, document{}, JSON, 0o640))
+	info, err := os.Stat(path)
+
+	require.NoError(t, err)
+	assert.Equal(t, os.FileMode(0o640), info.Mode().Perm())
+}
+
+func TestSaveFailedWriteLeavesExistingDocumentUnchanged(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "document.json")
+	require.NoError(t, Save(path, document{Name: "original"}, JSON, 0o600))
+
+	err := Save(filepath.Join(path, "child"), document{Name: "replacement"}, JSON, 0o600)
+
+	assert.Error(t, err)
+	loaded, loadErr := Load[document](path, JSON)
+	require.NoError(t, loadErr)
+	assert.Equal(t, "original", loaded.Name)
+}
+
+func TestSaveReturnsCodecErrors(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "document.json")
+	codec := failingCodec{err: errors.New("codec failed")}
+
+	err := Save(path, document{}, codec, 0o600)
+
+	assert.ErrorIs(t, err, codec.err)
+}
+
+type failingCodec struct{ err error }
+
+func (c failingCodec) Marshal(any) ([]byte, error) { return nil, c.err }
+
+func (c failingCodec) Unmarshal([]byte, any) error { return c.err }