Add first test for encoder code.

.gitignore

@@ -0,0 +1 @@
+testdata/output/

encoder_test.go

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+/*
+ * Go interface to libheif
+ *
+ * Copyright (c) 2018-2024 struktur AG, Joachim Bauch <[email protected]>
+ *
+ * libheif is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version.
+ *
+ * libheif is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with libheif.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package libheif
+
+import (
+	"bytes"
+	"image"
+	_ "image/jpeg"
+	_ "image/png"
+	"os"
+	"path"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func loadImage(t *testing.T, filename string) image.Image {
+	t.Helper()
+	require := require.New(t)
+	data, err := os.ReadFile(filename)
+	require.NoError(err)
+
+	img, _, err := image.Decode(bytes.NewBuffer(data))
+	require.NoError(err)
+	return img
+}
+
+func TestEncoder(t *testing.T) {
+	codecs := map[CompressionFormat]string{
+		CompressionHEVC: "heif",
+		CompressionAV1:  "avif",
+	}
+
+	outdir := "testdata/output"
+	err := os.MkdirAll(outdir, 0755)
+	require.NotErrorIs(t, err, os.ErrExist)
+
+	for codec, ext := range codecs {
+		codec := codec
+		ext := ext
+		t.Run(ext, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+			require.True(HaveEncoderForFormat(codec))
+
+			img := loadImage(t, "testdata/example-1.jpg")
+			ctx, err := EncodeFromImage(img, codec, 75, LosslessModeDisabled, LoggingLevelFull)
+			require.NoError(err)
+
+			output := path.Join(outdir, "example-1."+ext)
+			assert.NoError(ctx.WriteToFile(output))
+
+			var out bytes.Buffer
+			assert.NoError(ctx.Write(&out))
+
+			if assert.FileExists(output) {
+				if data, err := os.ReadFile(output); assert.NoError(err) {
+					assert.Equal(len(data), out.Len())
+				}
+			}
+		})
+	}
+
+}