diff --git a/crates/moon-core/src/config/detect_view/tests.rs b/crates/moon-core/src/config/detect_view/tests.rs
index 5480e711c..b3db645dd 100644
--- a/crates/moon-core/src/config/detect_view/tests.rs
+++ b/crates/moon-core/src/config/detect_view/tests.rs
@@ -73,3 +73,113 @@ fn detect_view_roundtrip_preserves_every_assignable_field() {
         );
     }
 }
+
+/// Mini is a 2×2 grid, medium a 2×3, and large a 3×3. Anything past large keeps the large grid.
+///
+/// Breakage: handing medium four slots, or an unknown size the mini grid, draws the wrong number
+/// of fields on the card. The products are the grids named on `detect_slot_count`, not its arms.
+#[test]
+fn slot_count_follows_the_card_grid() {
+    assert_eq!(detect_slot_count(DETECT_SIZE_MINI), 2 * 2);
+    assert_eq!(detect_slot_count(DETECT_SIZE_MEDIUM), 2 * 3);
+    assert_eq!(detect_slot_count(DETECT_SIZE_LARGE), 3 * 3);
+    assert_eq!(detect_slot_count(DETECT_SIZE_LARGE + 1), 3 * 3);
+}
+
+/// The colored server rail is at most five pixels. Zero stays off; one past the cap does not grow.
+///
+/// Breakage: dropping the cap, or stopping a pixel early, paints the server color across the coin.
+#[test]
+fn rail_width_clamps_to_five_pixels() {
+    let mut card = DetectSizeCfg {
+        rail_w: 0,
+        ..Default::default()
+    };
+    assert_eq!(card.rail_w_clamped(), 0);
+    card.rail_w = 5;
+    assert_eq!(card.rail_w_clamped(), 5);
+    card.rail_w = 6;
+    assert_eq!(card.rail_w_clamped(), 5);
+}
+
+/// The rail's gradient fade stops at the card's own width.
+///
+/// Breakage: forgetting the card width lets a stored gradient paint past the card.
+#[test]
+fn rail_gradient_clamps_to_the_card_width() {
+    let mut card = DetectSizeCfg {
+        w: 100,
+        rail_grad: 0,
+        ..Default::default()
+    };
+    assert_eq!(card.rail_grad_clamped(), 0);
+    card.rail_grad = 100;
+    assert_eq!(card.rail_grad_clamped(), 100);
+    card.rail_grad = 101;
+    assert_eq!(card.rail_grad_clamped(), 100);
+}
+
+/// The active size is mini, medium, or large. One past large stays large.
+///
+/// Breakage: clamping only as far as medium makes a stored large read as medium, and dropping the
+/// clamp lets a corrupt size through to the card picker.
+#[test]
+fn card_size_clamps_to_large() {
+    let mut cfg = DetectViewCfg {
+        size: DETECT_SIZE_MINI,
+        ..Default::default()
+    };
+    assert_eq!(cfg.size_clamped(), DETECT_SIZE_MINI);
+    cfg.size = DETECT_SIZE_MEDIUM;
+    assert_eq!(cfg.size_clamped(), DETECT_SIZE_MEDIUM);
+    cfg.size = DETECT_SIZE_LARGE;
+    assert_eq!(cfg.size_clamped(), DETECT_SIZE_LARGE);
+    cfg.size = DETECT_SIZE_LARGE + 1;
+    assert_eq!(cfg.size_clamped(), DETECT_SIZE_LARGE);
+}
+
+/// Delta figures show at most two decimal places. Zero stays a whole number.
+///
+/// Breakage: a cap of one hides a second place the user stored, and no cap prints a third.
+#[test]
+fn delta_decimals_clamp_to_two_places() {
+    let mut cfg = DetectViewCfg {
+        delta_decimals: 0,
+        ..Default::default()
+    };
+    assert_eq!(cfg.delta_decimals_clamped(), 0);
+    cfg.delta_decimals = 2;
+    assert_eq!(cfg.delta_decimals_clamped(), 2);
+    cfg.delta_decimals = 3;
+    assert_eq!(cfg.delta_decimals_clamped(), 2);
+}
+
+/// Chart-routed detects join the feed only for the group that asked, including the unnamed default
+/// group. A neighbour's flag, and a group that was never stored, stay out.
+///
+/// Breakage: reading any group's flag, or treating the empty name as "missing", either hides the
+/// window-default group's detects or shows another group's.
+#[test]
+fn add_to_chart_follows_only_the_named_group() {
+    let empty = DetectViewFile::default();
+    assert!(!empty.shows_add_to_chart(""));
+    assert!(!empty.shows_add_to_chart("alpha"));
+
+    let opted_in = DetectViewCfg {
+        show_add_to_chart: true,
+        ..Default::default()
+    };
+    let mut file = DetectViewFile::default();
+    file.set_group("alpha", opted_in);
+    assert!(file.shows_add_to_chart("alpha"));
+    assert!(!file.shows_add_to_chart("beta"));
+    assert!(!file.shows_add_to_chart(""));
+
+    let window_default = DetectViewCfg {
+        show_add_to_chart: true,
+        ..Default::default()
+    };
+    file.set_group("", window_default);
+    assert!(file.shows_add_to_chart(""));
+    assert!(!file.shows_add_to_chart("beta"));
+}