1 files changed, 78 insertions, 0 deletions
diff --git a/internal/compression/compression_test.go b/internal/compression/compression_test.go
new file mode 100644
index 0000000..5279dfe
--- /dev/null
+++ b/internal/compression/compression_test.go
@@ -0,0 +1,78 @@
+// Copyright 2020 Google LLC All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package compression
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"github.com/google/go-containerregistry/internal/and"
+	"github.com/google/go-containerregistry/internal/gzip"
+	"github.com/google/go-containerregistry/internal/zstd"
+)
+
+type Compressor = func(rc io.ReadCloser) io.ReadCloser
+type Decompressor = func(rc io.ReadCloser) (io.ReadCloser, error)
+
+func testPeekCompression(t *testing.T,
+	compressionExpected string,
+	compress Compressor,
+	decompress Decompressor,
+) {
+	content := "This is the input string."
+	contentBuf := bytes.NewBufferString(content)
+
+	compressed := compress(io.NopCloser(contentBuf))
+	compressionDetected, pr, err := PeekCompression(compressed)
+	if err != nil {
+		t.Error("PeekCompression() =", err)
+	}
+
+	if got := string(compressionDetected); got != compressionExpected {
+		t.Errorf("PeekCompression(); got %q, content %q", got, compressionExpected)
+	}
+
+	decompressed, err := decompress(withCloser(pr, compressed))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	b, err := io.ReadAll(decompressed)
+	if err != nil {
+		t.Error("ReadAll() =", err)
+	}
+
+	if got := string(b); got != content {
+		t.Errorf("ReadAll(); got %q, content %q", got, content)
+	}
+}
+
+func TestPeekCompression(t *testing.T) {
+	testPeekCompression(t, "gzip", gzip.ReadCloser, gzip.UnzipReadCloser)
+	testPeekCompression(t, "zstd", zstd.ReadCloser, zstd.UnzipReadCloser)
+
+	nopCompress := func(rc io.ReadCloser) io.ReadCloser { return rc }
+	nopDecompress := func(rc io.ReadCloser) (io.ReadCloser, error) { return rc, nil }
+
+	testPeekCompression(t, "none", nopCompress, nopDecompress)
+}
+
+func withCloser(pr PeekReader, rc io.ReadCloser) io.ReadCloser {
+	return &and.ReadCloser{
+		Reader:    pr,
+		CloseFunc: rc.Close,
+	}
+}