Improve D&D validation reliability

internal/modules/dnd/shared/source_ref_coverage_test.go

@@ -0,0 +1,69 @@
+package shared
+
+import (
+	"testing"
+
+	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
+)
+
+func TestChunkCoverageRequiresCompleteDocumentOrderedSpan(t *testing.T) {
+	doc := coverageDocument(30, 10, 20, 40)
+	index := source.NewDocumentIndex(doc)
+
+	for _, test := range []struct {
+		name  string
+		chunk *source.Chunk
+		ref   source.SourceRef
+		want  bool
+	}{
+		{name: "complete non-monotonic span", chunk: coverageChunk(doc.ID, 30, 10, 20), ref: coverageRef(doc.ID, 30, 20), want: true},
+		{name: "single unit", chunk: coverageChunk(doc.ID, 10), ref: coverageRef(doc.ID, 10, 10), want: true},
+		{name: "missing middle unit", chunk: coverageChunk(doc.ID, 30, 20), ref: coverageRef(doc.ID, 30, 20)},
+		{name: "only endpoints", chunk: coverageChunk(doc.ID, 30, 40), ref: coverageRef(doc.ID, 30, 40)},
+		{name: "reversed", chunk: coverageChunk(doc.ID, 30, 10), ref: coverageRef(doc.ID, 10, 30)},
+		{name: "wrong source", chunk: coverageChunk(doc.ID, 30), ref: coverageRef("other", 30, 30)},
+		{name: "missing endpoint", chunk: coverageChunk(doc.ID, 30), ref: coverageRef(doc.ID, 30, 999)},
+		{name: "nil chunk", ref: coverageRef(doc.ID, 30, 30)},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			coverage := NewChunkCoverage(test.chunk)
+			if got := coverage.Contains(index, doc, test.ref); got != test.want {
+				t.Fatalf("Contains() = %t, want %t", got, test.want)
+			}
+		})
+	}
+	if NewChunkCoverage(coverageChunk(doc.ID, 30)).Contains(source.DocumentIndex{}, nil, coverageRef(doc.ID, 30, 30)) {
+		t.Fatal("Contains() with nil document and zero index = true, want false")
+	}
+}
+
+func TestChunkCoverageDoesNotRetainMutableChunkState(t *testing.T) {
+	doc := coverageDocument(1, 2)
+	chunk := coverageChunk(doc.ID, 1, 2)
+	coverage := NewChunkCoverage(chunk)
+	chunk.SourceID = "changed"
+	chunk.Units[0].ID = 99
+	if !coverage.Contains(source.NewDocumentIndex(doc), doc, coverageRef(doc.ID, 1, 2)) {
+		t.Fatal("Contains() changed after mutating source chunk")
+	}
+}
+
+func coverageDocument(ids ...int) *source.SourceDocument {
+	doc := &source.SourceDocument{ID: "session", Units: make([]source.SourceUnit, len(ids))}
+	for index, id := range ids {
+		doc.Units[index] = source.SourceUnit{ID: id}
+	}
+	return doc
+}
+
+func coverageChunk(sourceID string, ids ...int) *source.Chunk {
+	chunk := &source.Chunk{SourceID: sourceID, Units: make([]source.SourceUnit, len(ids))}
+	for index, id := range ids {
+		chunk.Units[index] = source.SourceUnit{ID: id}
+	}
+	return chunk
+}
+
+func coverageRef(sourceID string, start, end int) source.SourceRef {
+	return source.SourceRef{SourceID: sourceID, StartUnitID: start, EndUnitID: end}
+}