stabilize package ID relative to encode-decode format cycles

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

test/integration/encode_decode_cycle_test.go

@@ -0,0 +1,61 @@
+package integration
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/anchore/syft/syft"
+
+	"github.com/sergi/go-diff/diffmatchpatch"
+
+	"github.com/anchore/syft/syft/sbom"
+
+	"github.com/anchore/syft/syft/format"
+	"github.com/stretchr/testify/assert"
+)
+
+// TestEncodeDecodeEncodeCycleComparison is testing for differences in how SBOM documents get encoded on multiple cycles.
+// By encding and decoding the sbom we can compare the differences between the set of resulting objects. However,
+// this requires specific comparisons being done, and select redactions/omissions being made. Additionally, there are
+// already unit tests on each format encoder-decoder for properly functioning comparisons in depth, so there is no need
+// to do an object-to-object comparison. For this reason this test focuses on a bytes-to-bytes comparison after an
+// encode-decode-encode loop which will detect lossy behavior in both directions.
+func TestEncodeDecodeEncodeCycleComparison(t *testing.T) {
+	tests := []struct {
+		format format.Option
+	}{
+		{
+			format: format.JSONOption,
+		},
+	}
+	for _, test := range tests {
+		t.Run(string(test.format), func(t *testing.T) {
+
+			originalCatalog, _, d, src := catalogFixtureImage(t, "image-pkg-coverage")
+
+			originalSBOM := sbom.SBOM{
+				Artifacts: sbom.Artifacts{
+					PackageCatalog: originalCatalog,
+					Distro:         d,
+				},
+				Source: src.Metadata,
+			}
+
+			by1, err := syft.Encode(originalSBOM, test.format)
+			assert.NoError(t, err)
+
+			newSBOM, newFormat, err := syft.Decode(bytes.NewReader(by1))
+			assert.NoError(t, err)
+			assert.Equal(t, test.format, newFormat)
+
+			by2, err := syft.Encode(*newSBOM, test.format)
+			assert.NoError(t, err)
+
+			if !assert.True(t, bytes.Equal(by1, by2)) {
+				dmp := diffmatchpatch.New()
+				diffs := dmp.DiffMain(string(by1), string(by2), true)
+				t.Errorf("diff: %s", dmp.DiffPrettyText(diffs))
+			}
+		})
+	}
+}