test(growth): add zscore compute test

test/growth/calc/z_score_test.exs

@@ -0,0 +1,24 @@
+defmodule Growth.Calc.ZScoreTest do
+  @moduledoc false
+
+  use ExUnit.Case, async: true
+
+  import Growth.Data, only: [sample: 0]
+
+  doctest Growth.Calc.ZScore
+
+  alias Growth.Calc.ZScore
+
+  describe "compute/4" do
+    for %{key: key} = params <- sample() do
+      @tag params: params
+      test "returns a z-score given a measurement and box-cox fitted values #{key}", %{
+        params: params
+      } do
+        %{zscore: zscore, measure: measure, l: l, m: m, s: s} = params
+
+        assert_in_delta ZScore.compute(measure, l, m, s), zscore, 0.12
+      end
+    end
+  end
+end