fix: write non-ASCII test fixtures as JSON escape sequences

golden_test.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"os"
 	"sort"
+	"strings"
 	"testing"
 )
 
@@ -67,3 +68,26 @@ func readJSON(t *testing.T, path string, v any) {
 		t.Fatalf("%s: %v", path, err)
 	}
 }
+
+// TestFixturesAreASCII keeps the fixtures robust: invisible characters such as
+// U+2028 and U+2029 must be escape sequences in the JSON, because editors and tools
+// strip or normalise them when they are written raw (which once silently turned
+// the line_sep fixture into plain "abc").
+func TestFixturesAreASCII(t *testing.T) {
+	for _, path := range []string{"testdata/blocknote_fixtures.json", "testdata/blocknote_golden.json"} {
+		b, err := os.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for i, c := range b {
+			if c >= 0x80 && path == "testdata/blocknote_fixtures.json" {
+				t.Fatalf("%s has a raw non-ASCII byte at offset %d; write it as an escape sequence", path, i)
+			}
+		}
+		for _, r := range []rune{0x2028, 0x2029, 0xFEFF} {
+			if strings.ContainsRune(string(b), r) {
+				t.Errorf("%s contains a raw %U; write it as an escape sequence", path, r)
+			}
+		}
+	}
+}

js/golden.test.ts

@@ -35,8 +35,12 @@ describe("BlockNote markdown golden output", () => {
 		for (const name of Object.keys(fixtures).sort()) {
 			actual[name] = await render(fixtures[name]);
 		}
-		await expect(`${JSON.stringify(actual, null, 1)}\n`).toMatchFileSnapshot(
-			goldenPath,
-		);
+		// U+2028, U+2029 and U+FEFF are valid raw in JSON but editors and tools
+		// strip or normalise them, so write them as escapes.
+		const json = JSON.stringify(actual, null, 1)
+			.replaceAll("\u2028", "\\u2028")
+			.replaceAll("\u2029", "\\u2029")
+			.replaceAll("\uFEFF", "\\uFEFF");
+		await expect(`${json}\n`).toMatchFileSnapshot(goldenPath);
 	});
 });