Add breaks test

src/metabase/feature_extraction/timeseries.clj

@@ -147,8 +147,10 @@
                       range  (- (apply max window) (apply min window))
                       ql     (q left)
                       qr     (q right)]
-                  {:eta (/ (reduce + (map (comp k.math/sq -) ql qr))
-                           3 (k.math/sq range))
+                  {:eta (if (zero? range)
+                          0
+                          (/ (reduce + (map (comp k.math/sq -) ql qr))
+                             3 (k.math/sq range)))
                    :x   pivot
                    :idx idx}))
               (partition half-period 1 series)

test/metabase/feature_extraction/timeseries_test.clj

@@ -43,7 +43,14 @@
 (expect
   true
   (every? (decompose :month ts) [:trend :residual :seasonal]))
-
 (expect
   nil
   (decompose 100 ts))
+
+(expect
+  [[99]
+   []]
+  [
+   (breaks 12 (map vector (range) (concat (repeat 100 10)
+                                          (repeat 100 20))))
+   (breaks 12 (map vector (range) (take 100 (cycle (range 10)))))])