test: unit tests for heading conversion, image alt, content facts and related settings

- ConvertContentH1 and ConvertTranslationH1 for post bodies and category
  pillar text
- SetImageAlt with several matches, repeated alt attributes and markup
  that only looks like an img
- the content facts outline, images, decorative images and embeds
- the related-posts mode and count

classes/headings_test.go

@@ -28,3 +28,41 @@ func TestConvertH1(t *testing.T) {
 		}
 	}
 }
+
+// TestConvertContentH1 pins the body pair: content_html's count when its
+// HTML had H1s, content's otherwise (a markdown body's H1 is only in its
+// rendered HTML), both converted.
+func TestConvertContentH1(t *testing.T) {
+	c, h, n := ConvertContentH1("# Title\n\ntext", "<h1>Title</h1><p>text</p>")
+	if c != "# Title\n\ntext" || h != "<h2>Title</h2><p>text</p>" || n != 1 {
+		t.Fatalf("markdown body = %q %q %d", c, h, n)
+	}
+	c, h, n = ConvertContentH1("<h1>a</h1><h1>b</h1>", "")
+	if c != "<h2>a</h2><h2>b</h2>" || h != "" || n != 2 {
+		t.Fatalf("HTML body without rendered HTML = %q %q %d", c, h, n)
+	}
+	if _, _, n := ConvertContentH1("<p>x</p>", "<p>x</p>"); n != 0 {
+		t.Fatal("no H1, nothing converted")
+	}
+	if CountH1(`<h1>a</h1><div><h1 class="x">b</h1></div><h2>c</h2>`) != 2 || CountH1("") != 0 {
+		t.Fatal("CountH1 is wrong")
+	}
+}
+
+// TestConvertTranslationH1 pins a locale's translated attributes,
+// changed in place: content and content_html converted, other attributes
+// and values that are not strings left alone (a category's pillar text
+// takes the same path as a post body).
+func TestConvertTranslationH1(t *testing.T) {
+	attrs := map[string]any{"title": "<h1>not content</h1>", "content": "<h1>Pillar</h1><p>x</p>", "content_html": 5}
+	if n := ConvertTranslationH1(attrs); n != 1 || attrs["content"] != "<h2>Pillar</h2><p>x</p>" || attrs["title"] != "<h1>not content</h1>" || attrs["content_html"] != 5 {
+		t.Fatalf("attrs = %v n=%d", attrs, n)
+	}
+	both := map[string]any{"content": "# T", "content_html": "<h1>T</h1>"}
+	if n := ConvertTranslationH1(both); n != 1 || both["content_html"] != "<h2>T</h2>" || both["content"] != "# T" {
+		t.Fatalf("both = %v n=%d", both, n)
+	}
+	if ConvertTranslationH1(nil) != 0 || ConvertTranslationH1(map[string]any{"title": "x"}) != 0 {
+		t.Fatal("nothing to convert")
+	}
+}