diff --git a/crates/ui-egui/src/bidi.rs b/crates/ui-egui/src/bidi.rs
index c5809c601..e08c6b9df 100644
--- a/crates/ui-egui/src/bidi.rs
+++ b/crates/ui-egui/src/bidi.rs
@@ -393,345 +393,4 @@ fn mirrored(c: char) -> char {
 }
 
 #[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn text_without_rtl_is_borrowed_unchanged() {
-        for s in ["", "report.pdf", "日本語の文字.pdf", "a (b) [c]", "caf\u{00E9} \u{200E}x"] {
-            assert!(matches!(visual(s), Cow::Borrowed(v) if v == s), "{s:?}");
-        }
-    }
-
-    #[test]
-    fn arabic_words_swap_and_the_extension_stays_last() {
-        // The reported name: "one two.pdf" in Arabic.
-        assert_eq!(visual("واحد اثنين.pdf"), "اثنين واحد.pdf");
-        assert_eq!(visual("ملف.pdf"), "ملف.pdf");
-        assert_eq!(visual("تقرير نهائي جدا.pdf"), "جدا نهائي تقرير.pdf");
-    }
-
-    #[test]
-    fn latin_and_numbers_keep_their_own_order() {
-        assert_eq!(visual("report واحد اثنين final.pdf"), "report اثنين واحد final.pdf");
-        // A number inside right-to-left text reads left to right, to the left of what precedes it.
-        assert_eq!(visual("ملف 2024.pdf"), "2024 ملف.pdf");
-        assert_eq!(visual(r"C:\Users\me\واحد اثنين\a.pdf"), r"C:\Users\me\اثنين واحد\a.pdf");
-    }
-
-    #[test]
-    fn hebrew_and_brackets() {
-        assert_eq!(visual("שלום עולם.pdf"), "עולם שלום.pdf");
-        // Brackets between right-to-left words flip with the direction.
-        assert_eq!(visual("واحد (اثنين) ثلاثة.pdf"), "ثلاثة (اثنين) واحد.pdf");
-    }
-
-    #[test]
-    fn direction_controls_are_not_drawn() {
-        assert_eq!(visual("\u{202B}واحد اثنين\u{202C}.pdf"), "اثنين واحد.pdf");
-        assert_eq!(visual("\u{200F}واحد\u{061C}"), "واحد");
-    }
-
-    #[test]
-    fn rtl_labels_read_right_to_left() {
-        // No right-to-left characters: unchanged.
-        for s in ["", "Save as…", "{n} pages", "日本語"] {
-            assert_eq!(display_rtl(s), s);
-        }
-        assert_eq!(display_rtl("حفظ"), "حفظ");
-        // "Save as…": the second word and the ellipsis end up on the left.
-        assert_eq!(display_rtl("حفظ باسم…"), "…باسم حفظ");
-        // Latin words and numbers keep their own order inside the line.
-        assert_eq!(display_rtl("إنشاء PDF من ملف"), "ملف من PDF إنشاء");
-        assert_eq!(display_rtl("تصدير إلى Microsoft Word الآن"), "الآن Microsoft Word إلى تصدير");
-        assert_eq!(display_rtl("صالح لمدة 5 سنوات"), "سنوات 5 لمدة صالح");
-        // Keyboard shortcuts are not reversed.
-        assert_eq!(display_rtl("طباعة (⌘P)"), "(⌘P) طباعة");
-        assert_eq!(display_rtl("تدوير العرض (⇧⌘+)"), "(⇧⌘+) العرض تدوير");
-        assert_eq!(display_rtl("التمرير مع ⌘ أيضًا"), "أيضًا ⌘ مع التمرير");
-        assert_eq!(display_rtl("نص (عادي)"), "(عادي) نص");
-    }
-
-    #[test]
-    fn rtl_labels_keep_placeholders_whole() {
-        // Two placeholders around a colon stay together, left to right: a file name and its error.
-        assert_eq!(display_rtl("تعذّر فتح {name}: {e}"), "{name}: {e} فتح تعذّر");
-        assert_eq!(display_rtl("فشل {label}، السبب {e}"), "{e} السبب ،{label} فشل");
-        assert_eq!(display_rtl("{n} صفحات"), "صفحات {n}");
-        assert_eq!(display_rtl("الصفحة {p} من {n}"), "{n} من {p} الصفحة");
-        // Adjacent placeholders keep their order, as numbers around a slash would.
-        assert_eq!(display_rtl("جارٍ البحث… {s}/{p}"), "{s}/{p} …البحث جارٍ");
-        // Braces that are not a placeholder are ordinary punctuation.
-        assert_eq!(display_rtl("حرف } واحد"), "واحد { حرف");
-        let many = format!("ا {}", "{a} ".repeat(200));
-        assert_eq!(display_rtl(&many).matches("{a}").count(), 200);
-    }
-
-    #[test]
-    fn rtl_labels_keep_their_edges() {
-        // Edge spaces and separator dots stay where the code concatenates.
-        assert_eq!(display_rtl(" (صفحة {p})"), " ({p} صفحة)");
-        assert_eq!(display_rtl(" · محمي بكلمة مرور"), " · مرور بكلمة محمي");
-        assert_eq!(display_rtl("سلسلة المفاتيح  ·  "), "المفاتيح سلسلة  ·  ");
-        // A caption's colon stays next to its widget; a sentence's colon ends the sentence.
-        assert_eq!(display_rtl("الاسم:"), "الاسم:");
-        assert_eq!(display_rtl("صادرة عن: "), "عن صادرة: ");
-        assert_eq!(display_rtl("اختر المعرّف الرقمي الذي تريد استخدامه:"), ":استخدامه تريد الذي الرقمي المعرّف اختر");
-        // Each line is its own paragraph.
-        assert_eq!(display_rtl("تعذّر عرض الصفحة.\n{e}"), ".الصفحة عرض تعذّر\n{e}");
-    }
-
-    #[test]
-    fn rtl_labels_never_panic_on_odd_input() {
-        let long = "ا {n} ".repeat(20_000);
-        for s in [
-            "ا{",
-            "ا}",
-            "ا{}",
-            "ا{{{",
-            "}ا{",
-            "ا\u{E000}{n}",
-            "⌘",
-            "ا ⌘",
-            "⌘ا⌘{",
-            "ا (⇧⌘",
-            "\u{064B}:",
-            ":",
-            "ا:",
-            " : ا : ",
-            "ا\n\n\nب",
-            "\u{202E}ا{n}",
-            long.as_str(),
-        ] {
-            let v = display_rtl(s);
-            assert!(v.chars().count() <= s.chars().count(), "{:?}", s.chars().take(12).collect::<String>());
-        }
-    }
-
-    /// `wrap` with a width of `n` characters.
-    fn wrap_at(text: &str, n: usize) -> Vec<Line> {
-        wrap(text, |s| s.chars().count() <= n)
-    }
-
-    fn rtl(text: &str) -> Line {
-        Line { text: text.to_owned(), rtl: true }
-    }
-
-    fn ltr(text: &str) -> Line {
-        Line { text: text.to_owned(), rtl: false }
-    }
-
-    /// Check that a Persian paragraph, including words joined by a zero-width non-joiner, reaches epaint as
-    /// one logical right-to-left run.
-    #[test]
-    fn persian_paragraph_keeps_logical_order_for_epaint() {
-        // The line stays in reading order; epaint shapes and reorders it (see `on_screen`).
-        assert_eq!(wrap_at("من به مدرسه می‌روم", 80), [rtl("من به مدرسه می‌روم")]);
-        // The zero-width non-joiner keeps a word whole, so the shaper gets it as one run.
-        assert_eq!(wrap_at("کتاب‌ها", 80), [rtl("کتاب‌ها")]);
-    }
-
-    /// Check that Arabic text wraps into lines in logical reading order rather than visual order.
-    #[test]
-    fn arabic_lines_break_in_reading_order() {
-        // The first words go on the first line, in logical order for epaint to reorder.
-        assert_eq!(wrap_at("واحد اثنين ثلاثة أربعة", 11), [rtl("واحد اثنين"), rtl("ثلاثة أربعة")]);
-        assert_eq!(wrap_at("واحد اثنين ثلاثة أربعة", 80), [rtl("واحد اثنين ثلاثة أربعة")]);
-    }
-
-    /// Check that each paragraph takes its base direction from its first strong character, not from leading
-    /// numbers or neutral text.
-    #[test]
-    fn base_direction_comes_from_the_first_strong_character() {
-        // Latin first: a left-to-right paragraph with an Arabic phrase inside it.
-        assert_eq!(wrap_at("See واحد اثنين here", 80), [ltr("See واحد اثنين here")]);
-        // Persian first: right to left, with the Latin words and number in reading order.
-        assert_eq!(wrap_at("فایل PDF نسخه 2 است", 80), [rtl("فایل PDF نسخه 2 است")]);
-        assert_eq!(wrap_at("سلام Hello World", 80), [rtl("سلام Hello World")]);
-        // Leading neutrals and numbers don't decide it.
-        assert_eq!(wrap_at("12. واحد اثنين", 80), [rtl("12. واحد اثنين")]);
-        // Each paragraph finds its own direction.
-        assert_eq!(wrap_at("واحد اثنين\nOK then\n\nשלום עולם", 80), [rtl("واحد اثنين"), ltr("OK then"), ltr(""), rtl("שלום עולם")]);
-    }
-
-    /// Check that right-to-left punctuation and brackets stay in logical order for epaint to mirror when
-    /// displaying.
-    #[test]
-    fn rtl_punctuation_and_brackets() {
-        // Logical text: epaint mirrors punctuation and brackets for display.
-        assert_eq!(wrap_at("سلام دنیا.", 80), [rtl("سلام دنیا.")]);
-        assert_eq!(wrap_at("واحد (اثنين) ثلاثة", 80), [rtl("واحد (اثنين) ثلاثة")]);
-        assert_eq!(wrap_at("آیا آماده است؟", 80), [rtl("آیا آماده است؟")]);
-    }
-
-    /// Check that Persian and Arabic-Indic digits stay in logical order inside a right-to-left paragraph.
-    #[test]
-    fn persian_digits_go_to_the_shaper_reversed() {
-        // Persian and Arabic-Indic digits stay in logical order; epaint's shaper preserves their
-        // left-to-right reading inside the right-to-left paragraph.
-        assert_eq!(wrap_at("سال ۱۴۰۲ شمسی", 80), [rtl("سال ۱۴۰۲ شمسی")]);
-        assert_eq!(wrap_at("صفحه ١٢", 80), [rtl("صفحه ١٢")]);
-        assert_eq!(wrap_at("ب۱۲", 80), [rtl("ب۱۲")]);
-    }
-
-    #[test]
-    fn wrapping_handles_odd_widths_and_input() {
-        assert_eq!(wrap_at("", 10), Vec::<Line>::new());
-        // A word wider than the line is broken between characters.
-        assert_eq!(wrap_at("abcdefghij واحد", 4), [ltr("abcd"), ltr("efgh"), ltr("ij"), ltr("واحد")]);
-        // Extra spaces between words don't make empty lines; \r\n is one break.
-        assert_eq!(wrap_at("واحد    اثنين\r\nب", 5), [rtl("واحد"), rtl("اثنين"), rtl("ب")]);
-        // Nothing fits: one character per line, never an endless loop.
-        assert_eq!(wrap("واحد", |_| false).len(), 4);
-        let long = "ا ب ۱ (ج) ".repeat(5_000);
-        for s in ["\u{202E}ا\u{202C}b", "\u{064B}", "\n\n", "\u{2029}ا", long.as_str()] {
-            let lines = wrap_at(s, 7);
-            let shown: usize = lines.iter().map(|l| l.text.chars().count()).sum();
-            assert!(shown <= s.chars().count(), "{:?}", s.chars().take(12).collect::<String>());
-        }
-    }
-
-    /// The characters egui puts on screen for each line of `text`, left to right, zero-width
-    /// ones left out, with the interface fonts.
-    fn on_screen(text: &str) -> Vec<String> {
-        let ctx = egui::Context::default();
-        ctx.set_fonts(crate::theme::font_definitions());
-        let mut shown = Vec::new();
-        let output = ctx.run_ui(egui::RawInput::default(), |ui| {
-            for line in wrap(text, |_| true) {
-                let galley = ui.painter().layout_no_wrap(line.text, egui::FontId::proportional(13.0), egui::Color32::WHITE);
-                let atlas = ui.fonts_mut(|fonts| fonts.image());
-                let mut visual = String::new();
-                for row in &galley.rows {
-                    // 0.37 keeps glyphs in logical order for selection. Read their actual
-                    // positions to test visual order instead of assuming vector order.
-                    let mut glyphs: Vec<_> = row.glyphs.iter().filter(|g| g.advance_width > 0.0).collect();
-                    glyphs.sort_by(|a, b| a.pos.x.total_cmp(&b.pos.x));
-                    visual.extend(glyphs.into_iter().map(|g| match g.chr {
-                        // `chr` remains logical even when the shaper mirrors the painted
-                        // bracket. Read the bitmap's middle-row ink to check what is visible.
-                        '(' | ')' => {
-                            let [x0, y0] = g.uv_rect.min.map(usize::from);
-                            let [x1, y1] = g.uv_rect.max.map(usize::from);
-                            let y = usize::midpoint(y0, y1);
-                            let ink: Vec<f32> = (x0..x1).map(|x| f32::from(atlas[(x, y)].a())).collect();
-                            let total: f32 = ink.iter().sum();
-                            assert!(total > 0.0 && !ink.is_empty(), "a bracket must have visible ink");
-                            let center = ink.iter().enumerate().map(|(i, alpha)| i as f32 * alpha).sum::<f32>() / total;
-                            if center < (ink.len() - 1) as f32 / 2.0 { '(' } else { ')' }
-                        }
-                        _ => g.chr,
-                    }));
-                }
-                shown.push(visual);
-            }
-        });
-        output.drop_without_applying_deltas();
-        shown
-    }
-
-    fn rev(s: &str) -> String {
-        s.chars().rev().collect()
-    }
-
-    #[test]
-    fn egui_draws_lines_in_reading_order() {
-        // Only with an Arabic-script face (the craft-fonts build input, as in CI); without one
-        // egui has no shaper run to check.
-        if pdfcraft_fonts::ui_arabic_fonts().is_empty() {
-            return;
-        }
-        assert_eq!(on_screen("من به مدرسه می\u{200C}روم"), [rev("من به مدرسه میروم")]);
-        assert_eq!(on_screen("فایل PDF نسخه 2 است"), [format!("{} 2 {} PDF {}", rev("است"), rev("نسخه"), rev("فایل"))]);
-        assert_eq!(on_screen("سال ۱۴۰۲ شمسی"), [format!("{} ۱۴۰۲ {}", rev("شمسی"), rev("سال"))]);
-        assert_eq!(on_screen("ب۱۲"), ["۱۲ب"]);
-        assert_eq!(on_screen("See واحد اثنين here"), [format!("See {} {} here", rev("اثنين"), rev("واحد"))]);
-        assert_eq!(on_screen("واحد (اثنين)."), [format!(".({}) {}", rev("اثنين"), rev("واحد"))]);
-    }
-
-    /// A file name keeps its extension at the visual end even when the first strong word is
-    /// Arabic: with an explicit `LeftToRight` base, `.pdf` is right of every Arabic glyph.
-    #[test]
-    fn file_names_are_laid_out_left_to_right() {
-        if pdfcraft_fonts::ui_arabic_fonts().is_empty() {
-            return;
-        }
-        let ctx = egui::Context::default();
-        ctx.set_fonts(crate::theme::font_definitions());
-        let mut positions: Vec<(char, f32)> = Vec::new();
-        ctx.run_ui(egui::RawInput::default(), |ui| {
-            let galley = layout_ltr(ui, "واحد اثنين.pdf", egui::FontId::proportional(13.0), egui::Color32::WHITE);
-            positions = galley.rows.iter().flat_map(|row| row.glyphs.iter().map(|g| (g.chr, g.pos.x))).collect();
-        })
-        .drop_without_applying_deltas();
-        let rightmost_arabic = positions.iter().filter(|(c, _)| is_rtl_script(*c)).map(|(_, x)| *x).fold(f32::MIN, f32::max);
-        let leftmost_extension = positions.iter().filter(|(c, _)| matches!(*c, '.' | 'p' | 'd' | 'f')).map(|(_, x)| *x).fold(f32::MAX, f32::min);
-        assert!(rightmost_arabic < leftmost_extension, "the extension must stay to the right: {positions:?}");
-        let last = positions.iter().filter(|(c, _)| !c.is_whitespace()).max_by(|a, b| a.1.total_cmp(&b.1));
-        assert_eq!(last.map(|(c, _)| *c), Some('f'), "the painted line ends in the extension");
-    }
-
-    /// Arabic/Kurdish labels get an explicit right-to-left paragraph, even when their first
-    /// strong character is Latin. With English the same text stays left to right.
-    #[test]
-    fn arabic_ui_labels_use_an_explicit_paragraph_direction() {
-        if pdfcraft_fonts::ui_arabic_fonts().is_empty() {
-            return;
-        }
-        let previous = crate::i18n::current();
-        let ctx = egui::Context::default();
-        ctx.set_fonts(crate::theme::font_definitions());
-        let read = |lang: &str| {
-            crate::i18n::set_current(crate::i18n::Lang::from_code(lang).expect("registered language"));
-            let mut got = None;
-            ctx.run_ui(egui::RawInput::default(), |ui| {
-                let galley = layout_ui(ui, "PDF واحد", egui::FontId::proportional(13.0), egui::Color32::WHITE);
-                let positions: Vec<_> = galley.rows.iter().flat_map(|row| row.glyphs.iter().map(|g| (g.chr, g.pos.x))).collect();
-                got = Some((galley.job.direction, positions));
-            })
-            .drop_without_applying_deltas();
-            got.expect("one layout")
-        };
-        let (direction, positions) = read("ar");
-        crate::i18n::set_current(previous);
-        assert_eq!(direction, egui::epaint::text::TextDirection::RightToLeft);
-        let p = positions.iter().find(|(c, _)| *c == 'P').map(|(_, x)| *x).expect("a Latin P");
-        let rightmost_arabic = positions.iter().filter(|(c, _)| is_rtl_script(*c)).map(|(_, x)| *x).fold(f32::MIN, f32::max);
-        assert!(p > rightmost_arabic, "in an RTL paragraph the first Latin run is at the right: {positions:?}");
-
-        let (direction, positions) = read("en");
-        crate::i18n::set_current(previous);
-        assert_eq!(direction, egui::epaint::text::TextDirection::Auto);
-        let p = positions.iter().find(|(c, _)| *c == 'P').map(|(_, x)| *x).expect("a Latin P");
-        let leftmost_arabic = positions.iter().filter(|(c, _)| is_rtl_script(*c)).map(|(_, x)| *x).fold(f32::MAX, f32::min);
-        assert!(p < leftmost_arabic, "with English the Latin run stays at the left: {positions:?}");
-    }
-
-    #[test]
-    fn single_line_with_its_own_direction() {
-        assert!(matches!(visual_auto("Ada Lovelace"), Cow::Borrowed("Ada Lovelace")));
-        assert_eq!(visual_auto("علی رضایی"), "رضایی علی");
-        assert_eq!(visual_auto("علی 2"), "2 علی");
-        assert_eq!(visual_auto("Team علی رضایی"), "Team رضایی علی");
-    }
-
-    #[test]
-    fn odd_input_never_panics() {
-        let long = "ا ب ".repeat(20_000);
-        let odd = [
-            "\u{064B}",
-            "\u{064B}\u{064C} \u{0301}",
-            "\u{202E}\u{202E}\u{202E}ا",
-            "\u{2067}ا\u{2066}b",
-            "ا\nب\r\nج\u{2029}د",
-            "\u{FEFF}ا\u{0000}ب",
-            "ا\u{10FFFF}\u{E000}ب",
-            "((((ا]]]]",
-            long.as_str(),
-        ];
-        for s in odd {
-            let v = visual(s);
-            assert!(v.chars().count() <= s.chars().count(), "{:?}", s.chars().take(12).collect::<String>());
-        }
-    }
-}
+mod tests;
diff --git a/crates/ui-egui/src/bidi/tests.rs b/crates/ui-egui/src/bidi/tests.rs
new file mode 100644
index 000000000..e57feebe2
--- /dev/null
+++ b/crates/ui-egui/src/bidi/tests.rs
@@ -0,0 +1,340 @@
+use super::*;
+
+#[test]
+fn text_without_rtl_is_borrowed_unchanged() {
+    for s in ["", "report.pdf", "日本語の文字.pdf", "a (b) [c]", "caf\u{00E9} \u{200E}x"] {
+        assert!(matches!(visual(s), Cow::Borrowed(v) if v == s), "{s:?}");
+    }
+}
+
+#[test]
+fn arabic_words_swap_and_the_extension_stays_last() {
+    // The reported name: "one two.pdf" in Arabic.
+    assert_eq!(visual("واحد اثنين.pdf"), "اثنين واحد.pdf");
+    assert_eq!(visual("ملف.pdf"), "ملف.pdf");
+    assert_eq!(visual("تقرير نهائي جدا.pdf"), "جدا نهائي تقرير.pdf");
+}
+
+#[test]
+fn latin_and_numbers_keep_their_own_order() {
+    assert_eq!(visual("report واحد اثنين final.pdf"), "report اثنين واحد final.pdf");
+    // A number inside right-to-left text reads left to right, to the left of what precedes it.
+    assert_eq!(visual("ملف 2024.pdf"), "2024 ملف.pdf");
+    assert_eq!(visual(r"C:\Users\me\واحد اثنين\a.pdf"), r"C:\Users\me\اثنين واحد\a.pdf");
+}
+
+#[test]
+fn hebrew_and_brackets() {
+    assert_eq!(visual("שלום עולם.pdf"), "עולם שלום.pdf");
+    // Brackets between right-to-left words flip with the direction.
+    assert_eq!(visual("واحد (اثنين) ثلاثة.pdf"), "ثلاثة (اثنين) واحد.pdf");
+}
+
+#[test]
+fn direction_controls_are_not_drawn() {
+    assert_eq!(visual("\u{202B}واحد اثنين\u{202C}.pdf"), "اثنين واحد.pdf");
+    assert_eq!(visual("\u{200F}واحد\u{061C}"), "واحد");
+}
+
+#[test]
+fn rtl_labels_read_right_to_left() {
+    // No right-to-left characters: unchanged.
+    for s in ["", "Save as…", "{n} pages", "日本語"] {
+        assert_eq!(display_rtl(s), s);
+    }
+    assert_eq!(display_rtl("حفظ"), "حفظ");
+    // "Save as…": the second word and the ellipsis end up on the left.
+    assert_eq!(display_rtl("حفظ باسم…"), "…باسم حفظ");
+    // Latin words and numbers keep their own order inside the line.
+    assert_eq!(display_rtl("إنشاء PDF من ملف"), "ملف من PDF إنشاء");
+    assert_eq!(display_rtl("تصدير إلى Microsoft Word الآن"), "الآن Microsoft Word إلى تصدير");
+    assert_eq!(display_rtl("صالح لمدة 5 سنوات"), "سنوات 5 لمدة صالح");
+    // Keyboard shortcuts are not reversed.
+    assert_eq!(display_rtl("طباعة (⌘P)"), "(⌘P) طباعة");
+    assert_eq!(display_rtl("تدوير العرض (⇧⌘+)"), "(⇧⌘+) العرض تدوير");
+    assert_eq!(display_rtl("التمرير مع ⌘ أيضًا"), "أيضًا ⌘ مع التمرير");
+    assert_eq!(display_rtl("نص (عادي)"), "(عادي) نص");
+}
+
+#[test]
+fn rtl_labels_keep_placeholders_whole() {
+    // Two placeholders around a colon stay together, left to right: a file name and its error.
+    assert_eq!(display_rtl("تعذّر فتح {name}: {e}"), "{name}: {e} فتح تعذّر");
+    assert_eq!(display_rtl("فشل {label}، السبب {e}"), "{e} السبب ،{label} فشل");
+    assert_eq!(display_rtl("{n} صفحات"), "صفحات {n}");
+    assert_eq!(display_rtl("الصفحة {p} من {n}"), "{n} من {p} الصفحة");
+    // Adjacent placeholders keep their order, as numbers around a slash would.
+    assert_eq!(display_rtl("جارٍ البحث… {s}/{p}"), "{s}/{p} …البحث جارٍ");
+    // Braces that are not a placeholder are ordinary punctuation.
+    assert_eq!(display_rtl("حرف } واحد"), "واحد { حرف");
+    let many = format!("ا {}", "{a} ".repeat(200));
+    assert_eq!(display_rtl(&many).matches("{a}").count(), 200);
+}
+
+#[test]
+fn rtl_labels_keep_their_edges() {
+    // Edge spaces and separator dots stay where the code concatenates.
+    assert_eq!(display_rtl(" (صفحة {p})"), " ({p} صفحة)");
+    assert_eq!(display_rtl(" · محمي بكلمة مرور"), " · مرور بكلمة محمي");
+    assert_eq!(display_rtl("سلسلة المفاتيح  ·  "), "المفاتيح سلسلة  ·  ");
+    // A caption's colon stays next to its widget; a sentence's colon ends the sentence.
+    assert_eq!(display_rtl("الاسم:"), "الاسم:");
+    assert_eq!(display_rtl("صادرة عن: "), "عن صادرة: ");
+    assert_eq!(display_rtl("اختر المعرّف الرقمي الذي تريد استخدامه:"), ":استخدامه تريد الذي الرقمي المعرّف اختر");
+    // Each line is its own paragraph.
+    assert_eq!(display_rtl("تعذّر عرض الصفحة.\n{e}"), ".الصفحة عرض تعذّر\n{e}");
+}
+
+#[test]
+fn rtl_labels_never_panic_on_odd_input() {
+    let long = "ا {n} ".repeat(20_000);
+    for s in [
+        "ا{",
+        "ا}",
+        "ا{}",
+        "ا{{{",
+        "}ا{",
+        "ا\u{E000}{n}",
+        "⌘",
+        "ا ⌘",
+        "⌘ا⌘{",
+        "ا (⇧⌘",
+        "\u{064B}:",
+        ":",
+        "ا:",
+        " : ا : ",
+        "ا\n\n\nب",
+        "\u{202E}ا{n}",
+        long.as_str(),
+    ] {
+        let v = display_rtl(s);
+        assert!(v.chars().count() <= s.chars().count(), "{:?}", s.chars().take(12).collect::<String>());
+    }
+}
+
+/// `wrap` with a width of `n` characters.
+fn wrap_at(text: &str, n: usize) -> Vec<Line> {
+    wrap(text, |s| s.chars().count() <= n)
+}
+
+fn rtl(text: &str) -> Line {
+    Line { text: text.to_owned(), rtl: true }
+}
+
+fn ltr(text: &str) -> Line {
+    Line { text: text.to_owned(), rtl: false }
+}
+
+/// Check that a Persian paragraph, including words joined by a zero-width non-joiner, reaches epaint as
+/// one logical right-to-left run.
+#[test]
+fn persian_paragraph_keeps_logical_order_for_epaint() {
+    // The line stays in reading order; epaint shapes and reorders it (see `on_screen`).
+    assert_eq!(wrap_at("من به مدرسه می‌روم", 80), [rtl("من به مدرسه می‌روم")]);
+    // The zero-width non-joiner keeps a word whole, so the shaper gets it as one run.
+    assert_eq!(wrap_at("کتاب‌ها", 80), [rtl("کتاب‌ها")]);
+}
+
+/// Check that Arabic text wraps into lines in logical reading order rather than visual order.
+#[test]
+fn arabic_lines_break_in_reading_order() {
+    // The first words go on the first line, in logical order for epaint to reorder.
+    assert_eq!(wrap_at("واحد اثنين ثلاثة أربعة", 11), [rtl("واحد اثنين"), rtl("ثلاثة أربعة")]);
+    assert_eq!(wrap_at("واحد اثنين ثلاثة أربعة", 80), [rtl("واحد اثنين ثلاثة أربعة")]);
+}
+
+/// Check that each paragraph takes its base direction from its first strong character, not from leading
+/// numbers or neutral text.
+#[test]
+fn base_direction_comes_from_the_first_strong_character() {
+    // Latin first: a left-to-right paragraph with an Arabic phrase inside it.
+    assert_eq!(wrap_at("See واحد اثنين here", 80), [ltr("See واحد اثنين here")]);
+    // Persian first: right to left, with the Latin words and number in reading order.
+    assert_eq!(wrap_at("فایل PDF نسخه 2 است", 80), [rtl("فایل PDF نسخه 2 است")]);
+    assert_eq!(wrap_at("سلام Hello World", 80), [rtl("سلام Hello World")]);
+    // Leading neutrals and numbers don't decide it.
+    assert_eq!(wrap_at("12. واحد اثنين", 80), [rtl("12. واحد اثنين")]);
+    // Each paragraph finds its own direction.
+    assert_eq!(wrap_at("واحد اثنين\nOK then\n\nשלום עולם", 80), [rtl("واحد اثنين"), ltr("OK then"), ltr(""), rtl("שלום עולם")]);
+}
+
+/// Check that right-to-left punctuation and brackets stay in logical order for epaint to mirror when
+/// displaying.
+#[test]
+fn rtl_punctuation_and_brackets() {
+    // Logical text: epaint mirrors punctuation and brackets for display.
+    assert_eq!(wrap_at("سلام دنیا.", 80), [rtl("سلام دنیا.")]);
+    assert_eq!(wrap_at("واحد (اثنين) ثلاثة", 80), [rtl("واحد (اثنين) ثلاثة")]);
+    assert_eq!(wrap_at("آیا آماده است؟", 80), [rtl("آیا آماده است؟")]);
+}
+
+/// Check that Persian and Arabic-Indic digits stay in logical order inside a right-to-left paragraph.
+#[test]
+fn persian_digits_go_to_the_shaper_reversed() {
+    // Persian and Arabic-Indic digits stay in logical order; epaint's shaper preserves their
+    // left-to-right reading inside the right-to-left paragraph.
+    assert_eq!(wrap_at("سال ۱۴۰۲ شمسی", 80), [rtl("سال ۱۴۰۲ شمسی")]);
+    assert_eq!(wrap_at("صفحه ١٢", 80), [rtl("صفحه ١٢")]);
+    assert_eq!(wrap_at("ب۱۲", 80), [rtl("ب۱۲")]);
+}
+
+#[test]
+fn wrapping_handles_odd_widths_and_input() {
+    assert_eq!(wrap_at("", 10), Vec::<Line>::new());
+    // A word wider than the line is broken between characters.
+    assert_eq!(wrap_at("abcdefghij واحد", 4), [ltr("abcd"), ltr("efgh"), ltr("ij"), ltr("واحد")]);
+    // Extra spaces between words don't make empty lines; \r\n is one break.
+    assert_eq!(wrap_at("واحد    اثنين\r\nب", 5), [rtl("واحد"), rtl("اثنين"), rtl("ب")]);
+    // Nothing fits: one character per line, never an endless loop.
+    assert_eq!(wrap("واحد", |_| false).len(), 4);
+    let long = "ا ب ۱ (ج) ".repeat(5_000);
+    for s in ["\u{202E}ا\u{202C}b", "\u{064B}", "\n\n", "\u{2029}ا", long.as_str()] {
+        let lines = wrap_at(s, 7);
+        let shown: usize = lines.iter().map(|l| l.text.chars().count()).sum();
+        assert!(shown <= s.chars().count(), "{:?}", s.chars().take(12).collect::<String>());
+    }
+}
+
+/// The characters egui puts on screen for each line of `text`, left to right, zero-width
+/// ones left out, with the interface fonts.
+fn on_screen(text: &str) -> Vec<String> {
+    let ctx = egui::Context::default();
+    ctx.set_fonts(crate::theme::font_definitions());
+    let mut shown = Vec::new();
+    let output = ctx.run_ui(egui::RawInput::default(), |ui| {
+        for line in wrap(text, |_| true) {
+            let galley = ui.painter().layout_no_wrap(line.text, egui::FontId::proportional(13.0), egui::Color32::WHITE);
+            let atlas = ui.fonts_mut(|fonts| fonts.image());
+            let mut visual = String::new();
+            for row in &galley.rows {
+                // 0.37 keeps glyphs in logical order for selection. Read their actual
+                // positions to test visual order instead of assuming vector order.
+                let mut glyphs: Vec<_> = row.glyphs.iter().filter(|g| g.advance_width > 0.0).collect();
+                glyphs.sort_by(|a, b| a.pos.x.total_cmp(&b.pos.x));
+                visual.extend(glyphs.into_iter().map(|g| match g.chr {
+                    // `chr` remains logical even when the shaper mirrors the painted
+                    // bracket. Read the bitmap's middle-row ink to check what is visible.
+                    '(' | ')' => {
+                        let [x0, y0] = g.uv_rect.min.map(usize::from);
+                        let [x1, y1] = g.uv_rect.max.map(usize::from);
+                        let y = usize::midpoint(y0, y1);
+                        let ink: Vec<f32> = (x0..x1).map(|x| f32::from(atlas[(x, y)].a())).collect();
+                        let total: f32 = ink.iter().sum();
+                        assert!(total > 0.0 && !ink.is_empty(), "a bracket must have visible ink");
+                        let center = ink.iter().enumerate().map(|(i, alpha)| i as f32 * alpha).sum::<f32>() / total;
+                        if center < (ink.len() - 1) as f32 / 2.0 { '(' } else { ')' }
+                    }
+                    _ => g.chr,
+                }));
+            }
+            shown.push(visual);
+        }
+    });
+    output.drop_without_applying_deltas();
+    shown
+}
+
+fn rev(s: &str) -> String {
+    s.chars().rev().collect()
+}
+
+#[test]
+fn egui_draws_lines_in_reading_order() {
+    // Only with an Arabic-script face (the craft-fonts build input, as in CI); without one
+    // egui has no shaper run to check.
+    if pdfcraft_fonts::ui_arabic_fonts().is_empty() {
+        return;
+    }
+    assert_eq!(on_screen("من به مدرسه می\u{200C}روم"), [rev("من به مدرسه میروم")]);
+    assert_eq!(on_screen("فایل PDF نسخه 2 است"), [format!("{} 2 {} PDF {}", rev("است"), rev("نسخه"), rev("فایل"))]);
+    assert_eq!(on_screen("سال ۱۴۰۲ شمسی"), [format!("{} ۱۴۰۲ {}", rev("شمسی"), rev("سال"))]);
+    assert_eq!(on_screen("ب۱۲"), ["۱۲ب"]);
+    assert_eq!(on_screen("See واحد اثنين here"), [format!("See {} {} here", rev("اثنين"), rev("واحد"))]);
+    assert_eq!(on_screen("واحد (اثنين)."), [format!(".({}) {}", rev("اثنين"), rev("واحد"))]);
+}
+
+/// A file name keeps its extension at the visual end even when the first strong word is
+/// Arabic: with an explicit `LeftToRight` base, `.pdf` is right of every Arabic glyph.
+#[test]
+fn file_names_are_laid_out_left_to_right() {
+    if pdfcraft_fonts::ui_arabic_fonts().is_empty() {
+        return;
+    }
+    let ctx = egui::Context::default();
+    ctx.set_fonts(crate::theme::font_definitions());
+    let mut positions: Vec<(char, f32)> = Vec::new();
+    ctx.run_ui(egui::RawInput::default(), |ui| {
+        let galley = layout_ltr(ui, "واحد اثنين.pdf", egui::FontId::proportional(13.0), egui::Color32::WHITE);
+        positions = galley.rows.iter().flat_map(|row| row.glyphs.iter().map(|g| (g.chr, g.pos.x))).collect();
+    })
+    .drop_without_applying_deltas();
+    let rightmost_arabic = positions.iter().filter(|(c, _)| is_rtl_script(*c)).map(|(_, x)| *x).fold(f32::MIN, f32::max);
+    let leftmost_extension = positions.iter().filter(|(c, _)| matches!(*c, '.' | 'p' | 'd' | 'f')).map(|(_, x)| *x).fold(f32::MAX, f32::min);
+    assert!(rightmost_arabic < leftmost_extension, "the extension must stay to the right: {positions:?}");
+    let last = positions.iter().filter(|(c, _)| !c.is_whitespace()).max_by(|a, b| a.1.total_cmp(&b.1));
+    assert_eq!(last.map(|(c, _)| *c), Some('f'), "the painted line ends in the extension");
+}
+
+/// Arabic/Kurdish labels get an explicit right-to-left paragraph, even when their first
+/// strong character is Latin. With English the same text stays left to right.
+#[test]
+fn arabic_ui_labels_use_an_explicit_paragraph_direction() {
+    if pdfcraft_fonts::ui_arabic_fonts().is_empty() {
+        return;
+    }
+    let previous = crate::i18n::current();
+    let ctx = egui::Context::default();
+    ctx.set_fonts(crate::theme::font_definitions());
+    let read = |lang: &str| {
+        crate::i18n::set_current(crate::i18n::Lang::from_code(lang).expect("registered language"));
+        let mut got = None;
+        ctx.run_ui(egui::RawInput::default(), |ui| {
+            let galley = layout_ui(ui, "PDF واحد", egui::FontId::proportional(13.0), egui::Color32::WHITE);
+            let positions: Vec<_> = galley.rows.iter().flat_map(|row| row.glyphs.iter().map(|g| (g.chr, g.pos.x))).collect();
+            got = Some((galley.job.direction, positions));
+        })
+        .drop_without_applying_deltas();
+        got.expect("one layout")
+    };
+    let (direction, positions) = read("ar");
+    crate::i18n::set_current(previous);
+    assert_eq!(direction, egui::epaint::text::TextDirection::RightToLeft);
+    let p = positions.iter().find(|(c, _)| *c == 'P').map(|(_, x)| *x).expect("a Latin P");
+    let rightmost_arabic = positions.iter().filter(|(c, _)| is_rtl_script(*c)).map(|(_, x)| *x).fold(f32::MIN, f32::max);
+    assert!(p > rightmost_arabic, "in an RTL paragraph the first Latin run is at the right: {positions:?}");
+
+    let (direction, positions) = read("en");
+    crate::i18n::set_current(previous);
+    assert_eq!(direction, egui::epaint::text::TextDirection::Auto);
+    let p = positions.iter().find(|(c, _)| *c == 'P').map(|(_, x)| *x).expect("a Latin P");
+    let leftmost_arabic = positions.iter().filter(|(c, _)| is_rtl_script(*c)).map(|(_, x)| *x).fold(f32::MAX, f32::min);
+    assert!(p < leftmost_arabic, "with English the Latin run stays at the left: {positions:?}");
+}
+
+#[test]
+fn single_line_with_its_own_direction() {
+    assert!(matches!(visual_auto("Ada Lovelace"), Cow::Borrowed("Ada Lovelace")));
+    assert_eq!(visual_auto("علی رضایی"), "رضایی علی");
+    assert_eq!(visual_auto("علی 2"), "2 علی");
+    assert_eq!(visual_auto("Team علی رضایی"), "Team رضایی علی");
+}
+
+#[test]
+fn odd_input_never_panics() {
+    let long = "ا ب ".repeat(20_000);
+    let odd = [
+        "\u{064B}",
+        "\u{064B}\u{064C} \u{0301}",
+        "\u{202E}\u{202E}\u{202E}ا",
+        "\u{2067}ا\u{2066}b",
+        "ا\nب\r\nج\u{2029}د",
+        "\u{FEFF}ا\u{0000}ب",
+        "ا\u{10FFFF}\u{E000}ب",
+        "((((ا]]]]",
+        long.as_str(),
+    ];
+    for s in odd {
+        let v = visual(s);
+        assert!(v.chars().count() <= s.chars().count(), "{:?}", s.chars().take(12).collect::<String>());
+    }
+}