1 files changed, 75 insertions, 0 deletions
diff --git a/internal/flamegraph/nativejson_test.go b/internal/flamegraph/nativejson_test.go
new file mode 100644
index 0000000..c76d327
--- /dev/null
+++ b/internal/flamegraph/nativejson_test.go
@@ -0,0 +1,75 @@
+package flamegraph
+
+import (
+	"encoding/json"
+	"os"
+	"testing"
+)
+
+type jsonNodeForTest struct {
+	Name     string            `json:"name"`
+	Value    uint64            `json:"value"`
+	Total    uint64            `json:"total"`
+	Children []jsonNodeForTest `json:"children"`
+}
+
+type jsonFlamegraphForTest struct {
+	Fields     []string        `json:"fields"`
+	CountField string          `json:"countField"`
+	Root       jsonNodeForTest `json:"root"`
+}
+
+func TestWriteJSONFromFileContainsFlamegraphTree(t *testing.T) {
+	dir := t.TempDir()
+	iorFile := writeTestIorZst(t, dir)
+
+	n := NewNativeSVG([]string{"comm", "path", "tracepoint"}, "count")
+	outFile, err := n.WriteJSONFromFile(iorFile)
+	if err != nil {
+		t.Fatalf("WriteJSONFromFile returned error: %v", err)
+	}
+
+	data, err := os.ReadFile(outFile)
+	if err != nil {
+		t.Fatalf("read output json: %v", err)
+	}
+
+	var payload jsonFlamegraphForTest
+	if err := json.Unmarshal(data, &payload); err != nil {
+		t.Fatalf("unmarshal output json: %v", err)
+	}
+
+	if payload.CountField != "count" {
+		t.Fatalf("count field = %q, want %q", payload.CountField, "count")
+	}
+	if len(payload.Fields) != 3 {
+		t.Fatalf("fields len = %d, want 3", len(payload.Fields))
+	}
+	if payload.Root.Name != "root" {
+		t.Fatalf("root name = %q, want %q", payload.Root.Name, "root")
+	}
+	if payload.Root.Total != 1 {
+		t.Fatalf("root total = %d, want 1", payload.Root.Total)
+	}
+	if len(payload.Root.Children) != 1 {
+		t.Fatalf("root children len = %d, want 1", len(payload.Root.Children))
+	}
+	if payload.Root.Children[0].Name != "tester" {
+		t.Fatalf("root child name = %q, want %q", payload.Root.Children[0].Name, "tester")
+	}
+}
+
+func TestWriteJSONFromFileCleansUpPartialOutputOnError(t *testing.T) {
+	dir := t.TempDir()
+	iorFile := writeTestIorZst(t, dir)
+
+	n := NewNativeSVG([]string{"invalidField"}, "count")
+	outFile, err := n.WriteJSONFromFile(iorFile)
+	if err == nil {
+		t.Fatal("expected error for invalid field, got nil")
+	}
+
+	if _, statErr := os.Stat(outFile); !os.IsNotExist(statErr) {
+		t.Fatalf("expected partial output to be removed, stat err=%v", statErr)
+	}
+}