diff --git a/sample_dataset/metabase/sample_dataset/generate.clj b/sample_dataset/metabase/sample_dataset/generate.clj
index fdeec5267a26201492d73b20ca4b1a835e1945a6..d51dd122abcb8ec9472e1af37607a1f90efc8246 100644
--- a/sample_dataset/metabase/sample_dataset/generate.clj
+++ b/sample_dataset/metabase/sample_dataset/generate.clj
@@ -295,7 +295,7 @@
   (let [n (count xs)]
     (map-indexed (fn [i x]
                    ; Limit the noise to [0.1, 2.1].
-                   (update x k * (+ 1 (* (/ i n) (- (rand 2) 0.9)))))
+                   (update x k * (+ 1 (* (/ i n) (- (* 2 (rand)) 0.9)))))
                  xs)))
 
 (defn- add-seasonality
diff --git a/src/metabase/feature_extraction/insights.clj b/src/metabase/feature_extraction/insights.clj
index 3271b223f7fe999464ed8b54ac1c3c79ead2906b..b2c2d35bfdba2f0d9554475531b55316a5f00309 100644
--- a/src/metabase/feature_extraction/insights.clj
+++ b/src/metabase/feature_extraction/insights.clj
@@ -83,7 +83,7 @@
   [resolution series]
   (when resolution
     (transduce
-     (comp (x/partition (ts/period-length resolution) 1
+     (comp (x/partition (ts/period-length resolution)
                         (comp (map second)
                               (x/reduce h/histogram)))
            (map-indexed (fn [idx histogram]
@@ -104,7 +104,7 @@
                                      (- (* n s-xx) (sq s-x))))
                                (- n 2)
                                (- (* n s-xx) (sq s-x)))]
-            (when (and (not= slope 0)
+            (when (and (not= slope 0.0)
                        (math/significant? (/ slope slope-error)
                                           (d/t-distribution (- n 2))
                                           (/ 0.05 2)))
@@ -183,8 +183,8 @@
    https://en.wikipedia.org/wiki/Stationary_process"
   [series resolution]
   (when-let [n (ts/period-length resolution)]
-    (transduce (comp (x/partition n 1 (comp (map second)
-                                            (x/reduce h/histogram)))
+    (transduce (comp (x/partition n  (comp (map second)
+                                          (x/reduce h/histogram)))
                      (map (fn [histogram]
                             {:mean (h.impl/mean histogram)
                              :var  (h.impl/variance histogram)}))
@@ -193,7 +193,7 @@
                  ([] true)
                  ([acc] acc)
                  ([_ [{mean1 :mean var1 :var} {mean2 :mean var2 :var}]]
-                  (if (= var1 var2 0)
+                  (if (= var1 var2 0.0)
                     true
                     (let [t (/ (- mean1 mean2)
                                (num/sqrt (/ (+ var1 var2) n)))
diff --git a/test/metabase/feature_extraction/insights_test.clj b/test/metabase/feature_extraction/insights_test.clj
new file mode 100644
index 0000000000000000000000000000000000000000..3a47a4db900abff4dc2d4ac0c4d4737d9df9e35d
--- /dev/null
+++ b/test/metabase/feature_extraction/insights_test.clj
@@ -0,0 +1,32 @@
+(ns metabase.feature-extraction.insights-test
+  (:require [expectations :refer :all]
+            [medley.core :as m]
+            [metabase.feature-extraction.insights :refer :all]))
+
+(expect
+  [true
+   nil]
+  (map :stationary [(stationary {:series     (m/indexed (repeat 100 1))
+                                 :resolution :month})
+                    (stationary {:series     (m/indexed (range 100))
+                                 :resolution :month})]))
+
+(expect
+  [{:mode :increasing}
+   {:mode :increasing}
+   nil]
+  (map :variation-trend
+       [(variation-trend {:series (map-indexed
+                                   (fn [i x]
+                                     [i (* x (+ 1 (* (/ i 100)
+                                                     (- (* 2 (rand)) 0.9))))])
+                                   (repeatedly 100 #(rand-int 10)))
+                          :resolution :month})
+        (variation-trend {:series (map-indexed
+                                   (fn [i x]
+                                     [i (* x (+ 1 (* (/ (- 100 i) 100)
+                                                     (- (* 2 (rand)) 0.9))))])
+                                   (repeatedly 100 rand))
+                          :resolution :month})
+        (variation-trend {:series (m/indexed (repeat 100 1))
+                          :resolution :month})]))