✨ Add missing tests for session bug fixes and uniform-spread?

Add indexed-access-with-default in fill_test.cljc to cover the two-arity
(nth fills i default) form on both valid and out-of-range indices, directly
exercising the CLJS Fills -nth path fixed in 593cf125.

Add segment-content->selrect-multi-line in path_data_test.cljc to cover
content->selrect on a subpath with multiple consecutive line-to commands
where move-p diverges from from-p, confirming the bounding box matches
both the expected coordinates and the reference implementation; this
guards the calculate-extremities fix in bb5a04c7.

Add types-uniform-spread? in colors_test.cljc to cover
app.common.types.color/uniform-spread?, which had no dedicated tests.
Exercises the uniform case (via uniform-spread), the two-stop edge case,
wrong-offset detection, and wrong-color detection.

Signed-off-by: Andrey Antukh <niwi@niwi.nz>

common/test/common_tests/colors_test.cljc

@@ -426,6 +426,27 @@
                {:color "#ffffff" :opacity 1.0 :offset 1.0}]]
     (t/is (false? (c/uniform-spread? stops)))))
 
+(t/deftest types-uniform-spread?
+  (t/testing "uniformly spread stops are detected as uniform"
+    (let [c1    {:color "#000000" :opacity 0.0 :offset 0.0}
+          c2    {:color "#ffffff" :opacity 1.0 :offset 1.0}
+          stops (colors/uniform-spread c1 c2 3)]
+      (t/is (true? (colors/uniform-spread? stops)))))
+  (t/testing "two-stop gradient is uniform by definition"
+    (let [stops [{:color "#ff0000" :opacity 1.0 :offset 0.0}
+                 {:color "#0000ff" :opacity 1.0 :offset 1.0}]]
+      (t/is (true? (colors/uniform-spread? stops)))))
+  (t/testing "stops with wrong offset are not uniform"
+    (let [stops [{:color "#000000" :opacity 0.0 :offset 0.0}
+                 {:color "#888888" :opacity 0.5 :offset 0.3}
+                 {:color "#ffffff" :opacity 1.0 :offset 1.0}]]
+      (t/is (false? (colors/uniform-spread? stops)))))
+  (t/testing "stops with correct offset but wrong color are not uniform"
+    (let [stops [{:color "#000000" :opacity 0.0 :offset 0.0}
+                 {:color "#aaaaaa" :opacity 0.5 :offset 0.5}
+                 {:color "#ffffff" :opacity 1.0 :offset 1.0}]]
+      (t/is (false? (colors/uniform-spread? stops))))))
+
 (t/deftest ac-interpolate-gradient
   (let [stops [{:color "#000000" :opacity 0.0 :offset 0.0}
                {:color "#ffffff" :opacity 1.0 :offset 1.0}]]

common/test/common_tests/types/fill_test.cljc

@@ -207,3 +207,18 @@
         fill1  (nth fills1 1)]
     (t/is (nil? fill1))
     (t/is (equivalent-fill? fill0 sample-fill-6))))
+
+(t/deftest indexed-access-with-default
+  (t/testing "nth with default returns fill for valid index"
+    ;; Regression: CLJS -nth with default had reversed d/in-range? args,
+    ;; so it always fell through to the default even for valid indices.
+    (let [fills    (types.fills/from-plain [sample-fill-6])
+          sentinel ::not-found
+          result   (nth fills 0 sentinel)]
+      (t/is (not= sentinel result))
+      (t/is (equivalent-fill? result sample-fill-6))))
+  (t/testing "nth with default returns default for out-of-range index"
+    (let [fills    (types.fills/from-plain [sample-fill-6])
+          sentinel ::not-found]
+      (t/is (= sentinel (nth fills 1 sentinel)))
+      (t/is (= sentinel (nth fills -1 sentinel))))))

common/test/common_tests/types/path_data_test.cljc

@@ -973,6 +973,31 @@
     (t/is (mth/close? 10.0 (:x2 rect) 0.1))
     (t/is (mth/close? 10.0 (:y2 rect) 0.1))))
 
+(t/deftest segment-content->selrect-multi-line
+  ;; Regression: calculate-extremities used move-p instead of from-p in
+  ;; the :line-to branch. For a subpath with multiple consecutive line-to
+  ;; commands, the selrect must still match the reference implementation.
+  (let [;; A subpath that starts away from the origin and has three
+        ;; line-to segments so that move-p diverges from from-p for the
+        ;; later segments.
+        segments [{:command :move-to :params {:x 5.0  :y 5.0}}
+                  {:command :line-to :params {:x 15.0 :y 0.0}}
+                  {:command :line-to :params {:x 20.0 :y 8.0}}
+                  {:command :line-to :params {:x 10.0 :y 12.0}}]
+        content  (path/content segments)
+        rect     (path.segment/content->selrect content)
+        ref-pts  (calculate-extremities segments)]
+
+    ;; Bounding box must enclose all four vertices exactly.
+    (t/is (some? rect))
+    (t/is (mth/close?  5.0 (:x1 rect) 0.1))
+    (t/is (mth/close?  0.0 (:y1 rect) 0.1))
+    (t/is (mth/close? 20.0 (:x2 rect) 0.1))
+    (t/is (mth/close? 12.0 (:y2 rect) 0.1))
+
+    ;; Must agree with the reference implementation.
+    (t/is (= ref-pts (calculate-extremities content)))))
+
 (t/deftest segment-content-center
   (let [content (path/content sample-content-square)
         center  (path.segment/content-center content)]