diff --git a/tests/test_app.py b/tests/test_app.py
index af0df46..227a3d3 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -6,6 +6,7 @@ from datetime import datetime, timedelta, timezone
 
 import pytest
 
+from somafm_tui import config
 from somafm_tui.api import Song
 from somafm_tui.app import SomaFMApp
 from somafm_tui.widgets.help import HelpScreen
@@ -70,11 +71,11 @@ async def test_boot_navigation_filter_favourite_visualizer_help() -> None:
         assert app.index == 0
 
         modes = set()
-        for _ in range(3):
+        for _ in range(len(config.VISUALIZERS)):
             await pilot.press("v")
             await pilot.pause()
             modes.add(app.visualizer)
-        assert modes == {"both", "bars", "wave"}
+        assert modes == set(config.VISUALIZERS)
 
         await pilot.press("question_mark")
         await pilot.pause()
diff --git a/tests/test_spectrum_panel.py b/tests/test_spectrum_panel.py
new file mode 100644
index 0000000..46954af
--- /dev/null
+++ b/tests/test_spectrum_panel.py
@@ -0,0 +1,103 @@
+"""Rendering tests for the waterfall, radial and braille visualisers."""
+
+from __future__ import annotations
+
+import math
+
+from somafm_tui import config
+from somafm_tui.spectrum import Frame, SpectrumEngine
+from somafm_tui.widgets.spectrum import (
+    VISUALIZER_LABELS,
+    WATERFALL_HISTORY,
+    SpectrumPanel,
+)
+
+
+def make_frame(level: float = 0.7) -> Frame:
+    bands = tuple(0.12 + 0.8 * max(0.0, math.sin(index / 4.0)) for index in range(72))
+    peaks = tuple(min(1.0, value + 0.05) for value in bands)
+    wave = tuple(level * math.sin(point / 9.0) for point in range(192))
+    return Frame(bands=bands, peaks=peaks, wave=wave, level=level, status="monitor")
+
+
+def make_panel() -> SpectrumPanel:
+    return SpectrumPanel(SpectrumEngine())
+
+
+def test_every_visualizer_has_a_border_label() -> None:
+    assert set(VISUALIZER_LABELS) == set(config.VISUALIZERS)
+
+
+def test_waterfall_records_one_column_per_tick() -> None:
+    panel = make_panel()
+    frame = make_frame()
+    panel._record(frame, tick=1)
+    panel._record(frame, tick=2)
+    panel._record(frame, tick=2)  # a second render in the same tick
+    assert len(panel._history) == 2
+    for tick in range(3, WATERFALL_HISTORY + 20):
+        panel._record(frame, tick)
+    assert len(panel._history) == WATERFALL_HISTORY
+
+
+def test_waterfall_scrolls_spectrogram_with_bass_at_the_bottom() -> None:
+    panel = make_panel()
+    # Quieter highs, louder bass, so the bottom rows must be fuller.
+    rising = Frame(
+        bands=tuple((71 - index) / 71 for index in range(72)),
+        peaks=tuple((71 - index) / 71 for index in range(72)),
+        wave=(0.0,) * 192,
+        level=0.5,
+        status="monitor",
+    )
+    for tick in range(30):
+        panel._record(rising, tick)
+    lines = panel._waterfall(40, 12, dim=False)
+    assert len(lines) == 12
+    assert {len(line.plain) for line in lines} == {40}
+    chars = "".join(line.plain for line in lines)
+    assert any(char in chars for char in "░▒▓█")
+    # History that does not fill the panel is padded blank on the left.
+    assert lines[0].plain[:9].strip() == ""
+    filled = [sum(1 for char in line.plain if char != " ") for line in lines]
+    assert filled[-1] > filled[0]
+
+
+def test_radial_spectrum_draws_a_ring_inside_the_panel() -> None:
+    panel = make_panel()
+    lines = panel._radial(make_frame(), 61, 21, phase=0, dim=False)
+    assert len(lines) == 21
+    assert {len(line.plain) for line in lines} == {61}
+    text = "".join(line.plain for line in lines)
+    assert text.count("█") > 10
+    assert text.count("·") > 4
+    # The corners are outside the circle.
+    assert lines[2].plain[:6].strip() == ""
+    assert lines[2].plain[-6:].strip() == ""
+
+
+def test_radial_falls_back_to_bars_when_too_small() -> None:
+    panel = make_panel()
+    lines = panel._radial(make_frame(), 12, 4, phase=0, dim=False)
+    assert len(lines) == 4
+    assert {len(line.plain) for line in lines} == {12}
+    assert any(char in "".join(line.plain for line in lines) for char in "█▄▅")
+
+
+def test_braille_oscilloscope_uses_subcell_dots() -> None:
+    panel = make_panel()
+    lines = panel._braille(make_frame(0.9), 40, 8, phase=0, dim=False)
+    assert len(lines) == 8
+    assert {len(line.plain) for line in lines} == {40}
+    chars = "".join(line.plain for line in lines)
+    assert all(char == " " or 0x2800 <= ord(char) <= 0x28FF for char in chars)
+    dots = [char for char in chars if 0x2800 <= ord(char) <= 0x28FF]
+    assert len(dots) > 20
+
+
+def test_braille_keeps_a_baseline_when_silent() -> None:
+    panel = make_panel()
+    silent = Frame((0.0,) * 72, (0.0,) * 72, (0.0,) * 192, 0.0, "idle")
+    lines = panel._braille(silent, 20, 6, phase=0, dim=True)
+    chars = "".join(line.plain for line in lines)
+    assert any(0x2800 <= ord(char) <= 0x28FF for char in chars)